From 6d29442b4ba1d2a12a886a017d0d622edfac3ffa Mon Sep 17 00:00:00 2001
From: Martin Raspaud <martin.raspaud@smhi.se>
Date: Wed, 28 Aug 2024 13:19:45 +0200
Subject: [PATCH] Revert "Fix quotes"

This reverts commit bc9f8fccb2209b7d9787ae44d95bb827e7879560.
---
 doc/source/conf.py                            |  34 +--
 pygac/__init__.py                             |   2 +-
 pygac/calibration/noaa.py                     |  52 ++--
 pygac/configuration.py                        |   8 +-
 pygac/correct_tsm_issue.py                    |   2 +-
 pygac/gac_io.py                               | 184 +++++++-------
 pygac/gac_klm.py                              |   8 +-
 pygac/gac_reader.py                           |   6 +-
 pygac/klm_reader.py                           | 110 ++++-----
 pygac/lac_klm.py                              |   8 +-
 pygac/lac_reader.py                           |   4 +-
 pygac/patmosx_coeff_reader.py                 | 100 ++++----
 pygac/pod_reader.py                           |  84 +++----
 pygac/reader.py                               | 148 ++++++------
 pygac/runner.py                               |  16 +-
 pygac/tests/test_io.py                        |  42 ++--
 pygac/tests/test_klm.py                       |  20 +-
 .../test_noaa_calibration_coefficients.py     |  14 +-
 pygac/tests/test_pod.py                       |  56 ++---
 pygac/tests/test_reader.py                    | 224 +++++++++---------
 pygac/tests/test_utils.py                     |  18 +-
 pygac/utils.py                                |  46 ++--
 pyproject.toml                                |   2 +-
 23 files changed, 594 insertions(+), 594 deletions(-)

diff --git a/doc/source/conf.py b/doc/source/conf.py
index e0690849..388725e1 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -25,33 +25,33 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ["sphinx.ext.autodoc", "sphinx.ext.doctest", "sphinx.ext.todo",
-              "sphinx.ext.inheritance_diagram"]
+extensions = ['sphinx.ext.autodoc', 'sphinx.ext.doctest', 'sphinx.ext.todo',
+              'sphinx.ext.inheritance_diagram']
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ["_templates"]
+templates_path = ['_templates']
 
 # The suffix of source filenames.
-source_suffix = ".rst"
+source_suffix = '.rst'
 
 # The encoding of source files.
 #source_encoding = 'utf-8-sig'
 
 # The master toctree document.
-master_doc = "index"
+master_doc = 'index'
 
 # General information about the project.
-project = u"pygac"
-copyright = u"2014, Abhay Devasthale, Martin Raspaud and Adam Dybbroe"
+project = u'pygac'
+copyright = u'2014, Abhay Devasthale, Martin Raspaud and Adam Dybbroe'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = "0.1"
+version = '0.1'
 # The full version, including alpha/beta/rc tags.
-release = "0.1"
+release = '0.1'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -82,7 +82,7 @@
 #show_authors = False
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = "sphinx"
+pygments_style = 'sphinx'
 
 # A list of ignored prefixes for module index sorting.
 #modindex_common_prefix = []
@@ -92,7 +92,7 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = "default"
+html_theme = 'default'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
@@ -121,7 +121,7 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ["_static"]
+html_static_path = ['_static']
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
@@ -165,7 +165,7 @@
 #html_file_suffix = None
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = "pygacdoc"
+htmlhelp_basename = 'pygacdoc'
 
 
 # -- Options for LaTeX output --------------------------------------------------
@@ -179,8 +179,8 @@
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass [howto/manual]).
 latex_documents = [
-  ("index", "pygac.tex", u"pygac Documentation",
-   u"Abhay Devasthale, Martin Raspaud and Adam Dybbroe", "manual"),
+  ('index', 'pygac.tex', u'pygac Documentation',
+   u'Abhay Devasthale, Martin Raspaud and Adam Dybbroe', 'manual'),
 ]
 
 # The name of an image file (relative to this directory) to place at the top of
@@ -212,6 +212,6 @@
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
-    ("index", "pygac", u"pygac Documentation",
-     [u"Abhay Devasthale, Martin Raspaud and Adam Dybbroe"], 1)
+    ('index', 'pygac', u'pygac Documentation',
+     [u'Abhay Devasthale, Martin Raspaud and Adam Dybbroe'], 1)
 ]
diff --git a/pygac/__init__.py b/pygac/__init__.py
index 8d073303..8c97fc85 100644
--- a/pygac/__init__.py
+++ b/pygac/__init__.py
@@ -36,4 +36,4 @@
 # add a NullHandler to prevent messages in sys.stderr if the using application does
 # not use logging, but pygac makes logging calls of severity WARNING and greater.
 # See https://docs.python.org/3/howto/logging.html (Configuring Logging for a Library)
-logging.getLogger("pygac").addHandler(logging.NullHandler())
+logging.getLogger('pygac').addHandler(logging.NullHandler())
diff --git a/pygac/calibration/noaa.py b/pygac/calibration/noaa.py
index 32960024..f038816b 100644
--- a/pygac/calibration/noaa.py
+++ b/pygac/calibration/noaa.py
@@ -68,7 +68,7 @@ def calibrate(ds, custom_coeffs=None, coeffs_file=None):
     delta = (start_time.astype("datetime64[D]") - start_time.astype("datetime64[Y]")).astype(int)
     jday = delta.astype(int) + 1
 
-    corr = ds.attrs["sun_earth_distance_correction_factor"]
+    corr = ds.attrs['sun_earth_distance_correction_factor']
 
     # how many reflective channels are there ?
     tot_ref = channels.shape[2] - 3
@@ -108,9 +108,9 @@ def calibrate(ds, custom_coeffs=None, coeffs_file=None):
 
 class CoeffStatus(Enum):
     """Indicates the status of calibration coefficients."""
-    NOMINAL = "nominal"
-    PROVISIONAL = "provisional"
-    EXPERIMENTAL = "experimental"
+    NOMINAL = 'nominal'
+    PROVISIONAL = 'provisional'
+    EXPERIMENTAL = 'experimental'
 
 
 class Calibrator:
@@ -122,17 +122,17 @@ class Calibrator:
         default_coeffs: dictonary containing default values for all spacecrafts
     """
     version_hashs = {
-        "963af9b66268475ed500ad7b37da33c5": {
-            "name": "PATMOS-x, v2017r1",
-            "status": CoeffStatus.NOMINAL
+        '963af9b66268475ed500ad7b37da33c5': {
+            'name': 'PATMOS-x, v2017r1',
+            'status': CoeffStatus.NOMINAL
         },
-        "689386c822de18a07194ac7fd71652ea": {
-            "name": "PATMOS-x, v2017r1, with provisional coefficients for MetOp-C",
-            "status": CoeffStatus.PROVISIONAL
+        '689386c822de18a07194ac7fd71652ea': {
+            'name': 'PATMOS-x, v2017r1, with provisional coefficients for MetOp-C',
+            'status': CoeffStatus.PROVISIONAL
         },
-        "e8735ec394ecdb87b7edcd261e72d2eb": {
-            "name": "PATMOS-x, v2023",
-            "status": CoeffStatus.PROVISIONAL
+        'e8735ec394ecdb87b7edcd261e72d2eb': {
+            'name': 'PATMOS-x, v2023',
+            'status': CoeffStatus.PROVISIONAL
         },
     }
     fields = [
@@ -141,7 +141,7 @@ class Calibrator:
         "to_eff_blackbody_slope", "date_of_launch", "d", "spacecraft", "version"
     ]
 
-    Calibrator = namedtuple("Calibrator", fields)
+    Calibrator = namedtuple('Calibrator', fields)
     default_coeffs = None
     default_file = None
     default_version = None
@@ -178,21 +178,21 @@ def __new__(cls, spacecraft, custom_coeffs=None, coeffs_file=None):
         for key in ("dark_count", "gain_switch", "s0", "s1", "s2"):
             arraycoeffs[key] = np.array([
                 coeffs[channel][key]
-                for channel in ("channel_1", "channel_2", "channel_3a")
+                for channel in ('channel_1', 'channel_2', 'channel_3a')
             ], dtype=float)
         # thermal channels
         for key in ("centroid_wavenumber", "space_radiance",
                     "to_eff_blackbody_intercept", "to_eff_blackbody_slope"):
             arraycoeffs[key] = np.array([
                 coeffs[channel][key]
-                for channel in ("channel_3b", "channel_4", "channel_5")
+                for channel in ('channel_3b', 'channel_4', 'channel_5')
             ], dtype=float)
         arraycoeffs["b"] = np.array([
             [
                 coeffs[channel][key]
                 for key in ("b0", "b1", "b2")
             ]
-            for channel in ("channel_3b", "channel_4", "channel_5")
+            for channel in ('channel_3b', 'channel_4', 'channel_5')
         ], dtype=float)
         # thermometers
         # Note, that "thermometer_0" does not exists, and is filled with zeros to
@@ -205,7 +205,7 @@ def __new__(cls, spacecraft, custom_coeffs=None, coeffs_file=None):
             for d in range(5)
         ], dtype=float)
         # parse date of launch
-        date_of_launch_str = coeffs["date_of_launch"].replace("Z", "+00:00")
+        date_of_launch_str = coeffs["date_of_launch"].replace('Z', '+00:00')
         if sys.version_info < (3, 7):
             # Note that here any time information is lost
             import dateutil.parser
@@ -240,7 +240,7 @@ def read_coeffs(cls, coeffs_file):
         else:
             LOG.debug("Read PyGAC internal calibration coefficients.")
             coeffs_file = files("pygac") / "data/calibration.json"
-        with open(coeffs_file, mode="rb") as json_file:
+        with open(coeffs_file, mode='rb') as json_file:
             content = json_file.read()
             coeffs = json.loads(content)
             version = cls._get_coeffs_version(content)
@@ -253,10 +253,10 @@ def _get_coeffs_version(cls, coeff_file_content):
         digest = md5_hash.hexdigest()
         version_dict = cls.version_hashs.get(
             digest,
-            {"name": None, "status": None}
+            {'name': None, 'status': None}
         )
-        version = version_dict["name"]
-        status = version_dict["status"]
+        version = version_dict['name']
+        status = version_dict['status']
         if version is None:
             warning = "Unknown calibration coefficients version!"
             warnings.warn(warning, RuntimeWarning)
@@ -265,7 +265,7 @@ def _get_coeffs_version(cls, coeff_file_content):
             LOG.info('Identified calibration coefficients version "%s".',
                      version)
             if status != CoeffStatus.NOMINAL:
-                warning = "Using {} calibration coefficients".format(status)
+                warning = 'Using {} calibration coefficients'.format(status)
                 warnings.warn(warning, RuntimeWarning)
                 LOG.warning(warning)
         return version
@@ -536,9 +536,9 @@ def calibrate_thermal(counts, prt, ict, space, line_numbers, channel, cal):
         wlength = 3
 
     weighting_function = np.ones(wlength, dtype=float) / wlength
-    tprt_convolved = np.convolve(tprt, weighting_function, "same")
-    ict_convolved = np.convolve(ict, weighting_function, "same")
-    space_convolved = np.convolve(space, weighting_function, "same")
+    tprt_convolved = np.convolve(tprt, weighting_function, 'same')
+    ict_convolved = np.convolve(ict, weighting_function, 'same')
+    space_convolved = np.convolve(space, weighting_function, 'same')
 
     # take care of the beginning and end
     tprt_convolved[0:(wlength - 1) // 2] = tprt_convolved[(wlength - 1) // 2]
diff --git a/pygac/configuration.py b/pygac/configuration.py
index 4ceb7eed..9ca301e2 100644
--- a/pygac/configuration.py
+++ b/pygac/configuration.py
@@ -42,7 +42,7 @@ class FileNotFoundError(OSError):
 class Configuration(configparser.ConfigParser, object):
     """Configuration container for pygac."""
 
-    config_file = ""
+    config_file = ''
 
     def read(self, config_file):
         """Read and parse the configuration file
@@ -69,8 +69,8 @@ def read(self, config_file):
     def get(self, *args, **kwargs):
         """python 2 compatibility for fallback attribute"""
         if sys.version_info.major < 3:
-            if "fallback" in kwargs:
-                fallback = kwargs.pop("fallback")
+            if 'fallback' in kwargs:
+                fallback = kwargs.pop('fallback')
             else:
                 fallback = None
             try:
@@ -99,7 +99,7 @@ def get_config(initialized=True):
         try:
             config_file = os.environ["PYGAC_CONFIG_FILE"]
         except KeyError:
-            LOG.error("Environment variable PYGAC_CONFIG_FILE not set!")
+            LOG.error('Environment variable PYGAC_CONFIG_FILE not set!')
             raise
         _config.read(config_file)
     return _config
diff --git a/pygac/correct_tsm_issue.py b/pygac/correct_tsm_issue.py
index 12ea6027..f940125f 100644
--- a/pygac/correct_tsm_issue.py
+++ b/pygac/correct_tsm_issue.py
@@ -409,7 +409,7 @@ def std_filter(data, box_size):
     # need to surround the data with NaNs to calculate values at the boundary
     padded_data = np.pad(
         data, (border, border),
-        mode="constant",
+        mode='constant',
         constant_values=np.nan
     )
     windows = _rolling_window(padded_data, size)
diff --git a/pygac/gac_io.py b/pygac/gac_io.py
index 5c2311d6..8b08b2d5 100644
--- a/pygac/gac_io.py
+++ b/pygac/gac_io.py
@@ -52,20 +52,20 @@ def save_gac(satellite_name,
              gac_file, meta_data,
              output_file_prefix, avhrr_dir, qual_dir, sunsatangles_dir):
 
-    midnight_scanline = meta_data["midnight_scanline"]
-    miss_lines = meta_data["missing_scanlines"]
-    corr = meta_data["sun_earth_distance_correction_factor"]
+    midnight_scanline = meta_data['midnight_scanline']
+    miss_lines = meta_data['missing_scanlines']
+    corr = meta_data['sun_earth_distance_correction_factor']
 
     last_scan_line_number = qual_flags[-1, 0]
 
     # Strip invalid coordinates
     first_valid_lat, last_valid_lat = strip_invalid_lat(lats)
     if first_valid_lat > start_line:
-        LOG.info("New start_line chosen (due to invalid lat/lon "
-                 "info) = " + str(first_valid_lat))
+        LOG.info('New start_line chosen (due to invalid lat/lon '
+                 'info) = ' + str(first_valid_lat))
     if end_line > last_valid_lat:
-        LOG.info("New end_line chosen (due to invalid lat/lon "
-                 "info) = " + str(last_valid_lat))
+        LOG.info('New end_line chosen (due to invalid lat/lon '
+                 'info) = ' + str(last_valid_lat))
 
     # Check user-defined scanlines
     start_line, end_line = check_user_scanlines(
@@ -209,35 +209,35 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     t_obj = time.strptime(enddate + endtime[0:6], "%Y%m%d%H%M%S")
     endtime_sec1970 = calendar.timegm(t_obj)
 
-    LOG.info("Output file prefix = " + str(output_file_prefix))
-    LOG.info("AVHRR data will be written to " + str(avhrr_dir))
-    ofn = os.path.join(avhrr_dir, (output_file_prefix + "_avhrr_" +
-                                   satellite_name + "_99999_" +
-                                   startdate + "T" + starttime + "Z_" +
-                                   enddate + "T" + endtime + "Z.h5"))
+    LOG.info('Output file prefix = ' + str(output_file_prefix))
+    LOG.info('AVHRR data will be written to ' + str(avhrr_dir))
+    ofn = os.path.join(avhrr_dir, (output_file_prefix + '_avhrr_' +
+                                   satellite_name + '_99999_' +
+                                   startdate + 'T' + starttime + 'Z_' +
+                                   enddate + 'T' + endtime + 'Z.h5'))
 
-    LOG.info("Filename: " + str(os.path.basename(ofn)))
+    LOG.info('Filename: ' + str(os.path.basename(ofn)))
 
     fout = h5py.File(ofn, "w")
 
-    dset1 = fout.create_dataset("/image1/data", dtype="int16", data=ref1)
-    dset2 = fout.create_dataset("/image2/data", dtype="int16", data=ref2)
-    dset3 = fout.create_dataset("/image3/data", dtype="int16", data=bt3)
-    dset4 = fout.create_dataset("/image4/data", dtype="int16", data=bt4)
-    dset5 = fout.create_dataset("/image5/data", dtype="int16", data=bt5)
-    dset6 = fout.create_dataset("/image6/data", dtype="int16", data=ref3)
-    dset7 = fout.create_dataset("/where/lat/data", dtype="int32",
+    dset1 = fout.create_dataset("/image1/data", dtype='int16', data=ref1)
+    dset2 = fout.create_dataset("/image2/data", dtype='int16', data=ref2)
+    dset3 = fout.create_dataset("/image3/data", dtype='int16', data=bt3)
+    dset4 = fout.create_dataset("/image4/data", dtype='int16', data=bt4)
+    dset5 = fout.create_dataset("/image5/data", dtype='int16', data=bt5)
+    dset6 = fout.create_dataset("/image6/data", dtype='int16', data=ref3)
+    dset7 = fout.create_dataset("/where/lat/data", dtype='int32',
                                 data=arrLat_full)
-    dset8 = fout.create_dataset("/where/lon/data", dtype="int32",
+    dset8 = fout.create_dataset("/where/lon/data", dtype='int32',
                                 data=arrLon_full)
     del dset8
     channellist = []
-    channellist.append("channel1".encode("utf8"))
-    channellist.append("channel2".encode("utf8"))
-    channellist.append("channel3b".encode("utf8"))
-    channellist.append("channel4".encode("utf8"))
-    channellist.append("channel5".encode("utf8"))
-    channellist.append("channel3a".encode("utf8"))
+    channellist.append("channel1".encode('utf8'))
+    channellist.append("channel2".encode('utf8'))
+    channellist.append("channel3b".encode('utf8'))
+    channellist.append("channel4".encode('utf8'))
+    channellist.append("channel5".encode('utf8'))
+    channellist.append("channel3a".encode('utf8'))
     dset10 = fout.create_dataset("/how/channel_list",
                                  data=channellist)
     del dset10
@@ -282,8 +282,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g1.attrs["product"] = np.string_("SATCH")
     g1.attrs["quantity"] = np.string_("REFL")
-    g1.attrs["dataset_name"] = np.string_("Channel 1 reflectance")
-    g1.attrs["units"] = np.string_("%")
+    g1.attrs["dataset_name"] = np.string_('Channel 1 reflectance')
+    g1.attrs["units"] = np.string_('%')
     g1.attrs["gain"] = np.float32(0.01)
     g1.attrs["offset"] = np.float32(0.0)
     g1.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -295,8 +295,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g2.attrs["product"] = np.string_("SATCH")
     g2.attrs["quantity"] = np.string_("REFL")
-    g2.attrs["dataset_name"] = np.string_("Channel 2 reflectance")
-    g2.attrs["units"] = np.string_("%")
+    g2.attrs["dataset_name"] = np.string_('Channel 2 reflectance')
+    g2.attrs["units"] = np.string_('%')
     g2.attrs["gain"] = np.float32(0.01)
     g2.attrs["offset"] = np.float32(0.0)
     g2.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -308,8 +308,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g6.attrs["product"] = np.string_("SATCH")
     g6.attrs["quantity"] = np.string_("REFL")
-    g6.attrs["dataset_name"] = np.string_("Channel 3a reflectance")
-    g6.attrs["units"] = np.string_("%")
+    g6.attrs["dataset_name"] = np.string_('Channel 3a reflectance')
+    g6.attrs["units"] = np.string_('%')
     g6.attrs["gain"] = np.float32(0.01)
     g6.attrs["offset"] = np.float32(0.0)
     g6.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -321,8 +321,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g3.attrs["product"] = np.string_("SATCH")
     g3.attrs["quantity"] = np.string_("TB")
-    g3.attrs["dataset_name"] = np.string_("Channel 3b brightness temperature")
-    g3.attrs["units"] = np.string_("K")
+    g3.attrs["dataset_name"] = np.string_('Channel 3b brightness temperature')
+    g3.attrs["units"] = np.string_('K')
     g3.attrs["gain"] = np.float32(0.01)
     g3.attrs["offset"] = np.float32(273.15)
     g3.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -334,8 +334,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g4.attrs["product"] = np.string_("SATCH")
     g4.attrs["quantity"] = np.string_("TB")
-    g4.attrs["dataset_name"] = np.string_("Channel 4 brightness temperature")
-    g4.attrs["units"] = np.string_("K")
+    g4.attrs["dataset_name"] = np.string_('Channel 4 brightness temperature')
+    g4.attrs["units"] = np.string_('K')
     g4.attrs["gain"] = np.float32(0.01)
     g4.attrs["offset"] = np.float32(273.15)
     g4.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -347,8 +347,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g5.attrs["product"] = np.string_("SATCH")
     g5.attrs["quantity"] = np.string_("TB")
-    g5.attrs["dataset_name"] = np.string_("Channel 5 brightness temperature")
-    g5.attrs["units"] = np.string_("K")
+    g5.attrs["dataset_name"] = np.string_('Channel 5 brightness temperature')
+    g5.attrs["units"] = np.string_('K')
     g5.attrs["gain"] = np.float32(0.01)
     g5.attrs["offset"] = np.float32(273.15)
     g5.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -358,8 +358,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g5.attrs["startdate"] = np.string_(startdate)
     g5.attrs["enddate"] = np.string_(enddate)
 
-    g7.attrs["dataset_name"] = np.string_("Latitude")
-    g7.attrs["units"] = np.string_("Deg")
+    g7.attrs["dataset_name"] = np.string_('Latitude')
+    g7.attrs["units"] = np.string_('Deg')
     g7.attrs["gain"] = np.float32(0.0010)
     g7.attrs["offset"] = np.float32(0.0)
     g7.attrs["missingdata"] = np.int32(MISSING_DATA_LATLON)
@@ -369,8 +369,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g7.attrs["startdate"] = np.string_(startdate)
     g7.attrs["enddate"] = np.string_(enddate)
 
-    g8.attrs["dataset_name"] = np.string_("Longitude")
-    g8.attrs["units"] = np.string_("Deg")
+    g8.attrs["dataset_name"] = np.string_('Longitude')
+    g8.attrs["units"] = np.string_('Deg')
     g8.attrs["gain"] = np.float32(0.0010)
     g8.attrs["offset"] = np.float32(0.0)
     g8.attrs["missingdata"] = np.int32(MISSING_DATA_LATLON)
@@ -419,25 +419,25 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     fout.close()
 
-    LOG.info("Sun and Satellite viewing angles will be " +
-             "written to " + str(sunsatangles_dir))
+    LOG.info('Sun and Satellite viewing angles will be ' +
+             'written to ' + str(sunsatangles_dir))
     ofn = os.path.join(sunsatangles_dir,
-                       (output_file_prefix + "_sunsatangles_" +
-                        satellite_name + "_99999_" + startdate +
-                        "T" + starttime + "Z_" +
-                        enddate + "T" + endtime + "Z.h5"))
+                       (output_file_prefix + '_sunsatangles_' +
+                        satellite_name + '_99999_' + startdate +
+                        'T' + starttime + 'Z_' +
+                        enddate + 'T' + endtime + 'Z.h5'))
 
-    LOG.info("Filename: " + str(os.path.basename(ofn)))
+    LOG.info('Filename: ' + str(os.path.basename(ofn)))
     fout = h5py.File(ofn, "w")
 
-    dset1 = fout.create_dataset("/image1/data", dtype="int16", data=arrSZA)
-    dset2 = fout.create_dataset("/image2/data", dtype="int16", data=arrSTZ)
-    dset3 = fout.create_dataset("/image3/data", dtype="int16", data=arrRAA)
-    dset4 = fout.create_dataset("/image4/data", dtype="int16", data=arrSAA)
-    dset5 = fout.create_dataset("/image5/data", dtype="int16", data=arrSTA)
-    dset6 = fout.create_dataset("/where/lat/data", dtype="int32",
+    dset1 = fout.create_dataset("/image1/data", dtype='int16', data=arrSZA)
+    dset2 = fout.create_dataset("/image2/data", dtype='int16', data=arrSTZ)
+    dset3 = fout.create_dataset("/image3/data", dtype='int16', data=arrRAA)
+    dset4 = fout.create_dataset("/image4/data", dtype='int16', data=arrSAA)
+    dset5 = fout.create_dataset("/image5/data", dtype='int16', data=arrSTA)
+    dset6 = fout.create_dataset("/where/lat/data", dtype='int32',
                                 data=arrLat_full)
-    dset7 = fout.create_dataset("/where/lon/data", dtype="int32",
+    dset7 = fout.create_dataset("/where/lon/data", dtype='int32',
                                 data=arrLon_full)
 
     del dset4, dset5, dset6, dset7
@@ -450,12 +450,12 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g5 = fout.require_group("/image5")
     g6 = fout.require_group("/where")
 
-    g1.attrs["description"] = np.string_("Solar zenith angle")
-    g2.attrs["description"] = np.string_("Satellite zenith angle")
+    g1.attrs["description"] = np.string_('Solar zenith angle')
+    g2.attrs["description"] = np.string_('Satellite zenith angle')
     g3.attrs["description"] = np.string_(
-        "Relative satellite-sun azimuth angle")
-    g4.attrs["description"] = np.string_("Solar azimuth angle")
-    g5.attrs["description"] = np.string_("Satellite azimuth angle")
+        'Relative satellite-sun azimuth angle')
+    g4.attrs["description"] = np.string_('Solar azimuth angle')
+    g5.attrs["description"] = np.string_('Satellite azimuth angle')
     g6.attrs["num_of_pixels"] = np.int32(arrSZA.shape[1])
     g6.attrs["num_of_lines"] = np.int32(arrSZA.shape[0])
     g6.attrs["xscale"] = np.float32(0.0)
@@ -476,8 +476,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g1.attrs["product"] = np.string_("SUNZ")
     g1.attrs["quantity"] = np.string_("DEG")
-    g1.attrs["dataset_name"] = np.string_("Solar zenith angle")
-    g1.attrs["units"] = np.string_("Deg")
+    g1.attrs["dataset_name"] = np.string_('Solar zenith angle')
+    g1.attrs["units"] = np.string_('Deg')
     g1.attrs["gain"] = np.float32(0.01)
     g1.attrs["offset"] = np.float32(0.0)
     g1.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -489,8 +489,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g2.attrs["product"] = np.string_("SATZ")
     g2.attrs["quantity"] = np.string_("DEG")
-    g2.attrs["dataset_name"] = np.string_("Satellite zenith angle")
-    g2.attrs["units"] = np.string_("Deg")
+    g2.attrs["dataset_name"] = np.string_('Satellite zenith angle')
+    g2.attrs["units"] = np.string_('Deg')
     g2.attrs["gain"] = np.float32(0.01)
     g2.attrs["offset"] = np.float32(0.0)
     g2.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -503,8 +503,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g3.attrs["product"] = np.string_("SSAZD")
     g3.attrs["quantity"] = np.string_("DEG")
     g3.attrs["dataset_name"] = np.string_(
-        "Relative satellite-sun azimuth angle")
-    g3.attrs["units"] = np.string_("Deg")
+        'Relative satellite-sun azimuth angle')
+    g3.attrs["units"] = np.string_('Deg')
     g3.attrs["gain"] = np.float32(0.01)
     g3.attrs["offset"] = np.float32(0.0)
     g3.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -516,8 +516,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g4.attrs["product"] = np.string_("SUNA")
     g4.attrs["quantity"] = np.string_("DEG")
-    g4.attrs["dataset_name"] = np.string_("Solar azimuth angle")
-    g4.attrs["units"] = np.string_("Deg")
+    g4.attrs["dataset_name"] = np.string_('Solar azimuth angle')
+    g4.attrs["units"] = np.string_('Deg')
     g4.attrs["gain"] = np.float32(0.01)
     g4.attrs["offset"] = np.float32(0.0)
     g4.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -529,8 +529,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     g5.attrs["product"] = np.string_("SATA")
     g5.attrs["quantity"] = np.string_("DEG")
-    g5.attrs["dataset_name"] = np.string_("Satellite azimuth angle")
-    g5.attrs["units"] = np.string_("Deg")
+    g5.attrs["dataset_name"] = np.string_('Satellite azimuth angle')
+    g5.attrs["units"] = np.string_('Deg')
     g5.attrs["gain"] = np.float32(0.01)
     g5.attrs["offset"] = np.float32(0.0)
     g5.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -540,8 +540,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g5.attrs["startdate"] = np.string_(startdate)
     g5.attrs["enddate"] = np.string_(enddate)
 
-    g6.attrs["dataset_name"] = np.string_("Latitude")
-    g6.attrs["units"] = np.string_("Deg")
+    g6.attrs["dataset_name"] = np.string_('Latitude')
+    g6.attrs["units"] = np.string_('Deg')
     g6.attrs["gain"] = np.float32(0.0010)
     g6.attrs["offset"] = np.float32(0.0)
     g6.attrs["missingdata"] = np.int32(MISSING_DATA_LATLON)
@@ -551,8 +551,8 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g6.attrs["startdate"] = np.string_(startdate)
     g6.attrs["enddate"] = np.string_(enddate)
 
-    g7.attrs["dataset_name"] = np.string_("Longitude")
-    g7.attrs["units"] = np.string_("Deg")
+    g7.attrs["dataset_name"] = np.string_('Longitude')
+    g7.attrs["units"] = np.string_('Deg')
     g7.attrs["gain"] = np.float32(0.0010)
     g7.attrs["offset"] = np.float32(0.0)
     g7.attrs["missingdata"] = np.int32(MISSING_DATA_LATLON)
@@ -583,25 +583,25 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
 
     fout.close()
 
-    LOG.info("Quality flags will be " +
-             "written to " + str(qual_dir))
+    LOG.info('Quality flags will be ' +
+             'written to ' + str(qual_dir))
     ofn = os.path.join(qual_dir,
-                       (output_file_prefix + "_qualflags_" +
-                        satellite_name + "_99999_" + startdate +
-                        "T" + starttime + "Z_" +
-                        enddate + "T" + endtime + "Z.h5"))
+                       (output_file_prefix + '_qualflags_' +
+                        satellite_name + '_99999_' + startdate +
+                        'T' + starttime + 'Z_' +
+                        enddate + 'T' + endtime + 'Z.h5'))
 
-    LOG.info("Filename: " + str(os.path.basename(ofn)))
+    LOG.info('Filename: ' + str(os.path.basename(ofn)))
     fout = h5py.File(ofn, "w")
 
     g1 = fout.require_group("/qual_flags")
-    dset1 = g1.create_dataset("data", dtype="int16", data=qual_flags)
+    dset1 = g1.create_dataset("data", dtype='int16', data=qual_flags)
     del dset1
 
     g1.attrs["product"] = np.string_("QFLAG")
     g1.attrs["quantity"] = np.string_("INT")
-    g1.attrs["dataset_name"] = np.string_("Scanline quality flags")
-    g1.attrs["units"] = np.string_("None")
+    g1.attrs["dataset_name"] = np.string_('Scanline quality flags')
+    g1.attrs["units"] = np.string_('None')
     g1.attrs["gain"] = np.int32(1)
     g1.attrs["offset"] = np.int32(0)
     g1.attrs["missingdata"] = np.int32(MISSING_DATA)
@@ -615,13 +615,13 @@ def avhrrGAC_io(satellite_name, xutcs, startdate, enddate, starttime, endtime,
     g1.attrs["last_scan_line_number"] = last_scan_line_number
 
     g2 = fout.require_group("/ancillary")
-    dset2 = g2.create_dataset("missing_scanlines", dtype="int16",
+    dset2 = g2.create_dataset("missing_scanlines", dtype='int16',
                               data=miss_lines)
     del dset2
-    dset3 = g2.create_dataset("scanline_timestamps", dtype="int64",
-                              data=xutcs.astype("int64"))
-    dset3.attrs["units"] = "Milliseconds since 1970-01-01 00:00:00 UTC"
-    dset3.attrs["calendar"] = "standard"
+    dset3 = g2.create_dataset("scanline_timestamps", dtype='int64',
+                              data=xutcs.astype('int64'))
+    dset3.attrs['units'] = 'Milliseconds since 1970-01-01 00:00:00 UTC'
+    dset3.attrs['calendar'] = 'standard'
     g2.attrs["midnight_scanline"] = np.string_(midnight_scanline)
 
     fout.close()
diff --git a/pygac/gac_klm.py b/pygac/gac_klm.py
index 7d086974..3613ab01 100644
--- a/pygac/gac_klm.py
+++ b/pygac/gac_klm.py
@@ -134,10 +134,10 @@
                      ("frame_sync", ">u2", (6, )),
                      ("id", ">u2", (2, )),
                      ("time_code", ">u2", (4, )),
-                     ("telemetry", [("ramp_calibration", ">u2", (5, )),
-                                    ("PRT", ">u2", (3, )),
-                                    ("ch3_patch_temp", ">u2"),
-                                    ("spare", ">u2"), ]),
+                     ('telemetry', [("ramp_calibration", '>u2', (5, )),
+                                    ("PRT", '>u2', (3, )),
+                                    ("ch3_patch_temp", '>u2'),
+                                    ("spare", '>u2'), ]),
                      ("back_scan", ">u2", (30, )),
                      ("space_data", ">u2", (50, )),
                      ("sync_delta", ">u2"),
diff --git a/pygac/gac_reader.py b/pygac/gac_reader.py
index ecf3efeb..daa82e12 100644
--- a/pygac/gac_reader.py
+++ b/pygac/gac_reader.py
@@ -58,9 +58,9 @@ def _validate_header(cls, header):
         # call super to enter the Method Resolution Order (MRO)
         super(GACReader, cls)._validate_header(header)
         LOG.debug("validate header")
-        data_set_name = header["data_set_name"].decode()
+        data_set_name = header['data_set_name'].decode()
         # split header into parts
         creation_site, transfer_mode, platform_id = (
-            data_set_name.split(".")[:3])
-        if transfer_mode != "GHRR":
+            data_set_name.split('.')[:3])
+        if transfer_mode != 'GHRR':
             raise ReaderError('Improper transfer mode "%s"!' % transfer_mode)
diff --git a/pygac/klm_reader.py b/pygac/klm_reader.py
index db840a82..acc572ef 100644
--- a/pygac/klm_reader.py
+++ b/pygac/klm_reader.py
@@ -579,60 +579,60 @@ class KLM_QualityIndicator(IntFlag):
                                 ("zero_fill9", ">i2")])
 
 
-ars_header = np.dtype([("COST_number", "S6"),
-                       ("SAA_number", "S8"),
-                       ("order_creation_year", "S4"),
-                       ("order_creation_day_of_year", "S3"),
-                       ("processing_site_code", "S1"),
-                       ("processing_software", "S8"),
+ars_header = np.dtype([('COST_number', 'S6'),
+                       ('SAA_number', 'S8'),
+                       ('order_creation_year', 'S4'),
+                       ('order_creation_day_of_year', 'S3'),
+                       ('processing_site_code', 'S1'),
+                       ('processing_software', 'S8'),
                        # data selection criteria
-                       ("data_set_name", "S42"),
-                       ("ascii_blank_", "S2"),
-                       ("select_flag", "S1"),
-                       ("beginning_latitude", "S3"),
-                       ("ending_latitude", "S3"),
-                       ("beginning_longitude", "S4"),
-                       ("ending_longitude", "S4"),
-                       ("start_hour", "S2"),
-                       ("start_minute", "S2"),
-                       ("number_of_minutes", "S3"),
-                       ("appended_data_flag", "S1"),
-                       ("channel_select_flag", "S1", (20, )),
+                       ('data_set_name', 'S42'),
+                       ('ascii_blank_', 'S2'),
+                       ('select_flag', 'S1'),
+                       ('beginning_latitude', 'S3'),
+                       ('ending_latitude', 'S3'),
+                       ('beginning_longitude', 'S4'),
+                       ('ending_longitude', 'S4'),
+                       ('start_hour', 'S2'),
+                       ('start_minute', 'S2'),
+                       ('number_of_minutes', 'S3'),
+                       ('appended_data_flag', 'S1'),
+                       ('channel_select_flag', 'S1', (20, )),
                        # dataset summary
-                       ("ascii_blank__", "S29"),
-                       ("ascend_descend_flag", "S1"),
-                       ("first_latitude", "S3"),
-                       ("last_latitude", "S3"),
-                       ("first_longitude", "S4"),
-                       ("last_longitude", "S4"),
-                       ("data_format", "S20"),
-                       ("size_of_record", "S6"),
-                       ("number_of_records", "S6"),
+                       ('ascii_blank__', 'S29'),
+                       ('ascend_descend_flag', 'S1'),
+                       ('first_latitude', 'S3'),
+                       ('last_latitude', 'S3'),
+                       ('first_longitude', 'S4'),
+                       ('last_longitude', 'S4'),
+                       ('data_format', 'S20'),
+                       ('size_of_record', 'S6'),
+                       ('number_of_records', 'S6'),
                        # filler
-                       ("ascii_blank", "S319")
+                       ('ascii_blank', 'S319')
                        ])
 
 
 class KLMReader(Reader):
     """Reader for KLM data."""
 
-    spacecraft_names = {4: "noaa15",
-                        2: "noaa16",
-                        6: "noaa17",
-                        7: "noaa18",
-                        8: "noaa19",
-                        12: "metopa",
-                        11: "metopb",
-                        13: "metopc",
+    spacecraft_names = {4: 'noaa15',
+                        2: 'noaa16',
+                        6: 'noaa17',
+                        7: 'noaa18',
+                        8: 'noaa19',
+                        12: 'metopa',
+                        11: 'metopb',
+                        13: 'metopc',
                         }
-    spacecrafts_orbital = {4: "noaa 15",
-                           2: "noaa 16",
-                           6: "noaa 17",
-                           7: "noaa 18",
-                           8: "noaa 19",
-                           12: "metop 02",
-                           11: "metop 01",
-                           13: "metop 03",
+    spacecrafts_orbital = {4: 'noaa 15',
+                           2: 'noaa 16',
+                           6: 'noaa 17',
+                           7: 'noaa 18',
+                           8: 'noaa 19',
+                           12: 'metop 02',
+                           11: 'metop 01',
+                           13: 'metop 03',
                            }
 
     tsm_affected_intervals = TSM_AFFECTED_INTERVALS_KLM
@@ -659,7 +659,7 @@ def read(self, filename, fileobj=None):
         # file objects to (io.FileIO, io.BufferedReader, io.BufferedWriter)
         # see: numpy.compat.py3k.isfileobj
         self.filename = filename
-        LOG.info("Reading %s", self.filename)
+        LOG.info('Reading %s', self.filename)
         with file_opener(fileobj or filename) as fd_:
             self.ars_head, self.head = self.read_header(
                 filename, fileobj=fd_)
@@ -678,7 +678,7 @@ def read(self, filename, fileobj=None):
                     fd_.read(analog_telemetry_v2.itemsize),
                     dtype=analog_telemetry_v2, count=1)
             # LAC: 1, GAC: 2, ...
-            self.data_type = self.head["data_type_code"]
+            self.data_type = self.head['data_type_code']
             # read until end of file
             fd_.seek(self.offset + ars_offset, 0)
             buffer = fd_.read()
@@ -705,7 +705,7 @@ def read_header(cls, filename, fileobj=None):
             _ars_head, = np.frombuffer(
                 fd_.read(ars_header.itemsize),
                 dtype=ars_header, count=1)
-            if _ars_head["data_format"].startswith(b"NOAA Level 1b"):
+            if _ars_head['data_format'].startswith(b'NOAA Level 1b'):
                 ars_head = _ars_head.copy()
             else:
                 fd_.seek(0)
@@ -724,11 +724,11 @@ def _validate_header(cls, header):
         # call super to enter the Method Resolution Order (MRO)
         super(KLMReader, cls)._validate_header(header)
         LOG.debug("validate header")
-        data_set_name = header["data_set_name"].decode()
+        data_set_name = header['data_set_name'].decode()
         # split header into parts
         creation_site, transfer_mode, platform_id = (
-            data_set_name.split(".")[:3])
-        allowed_ids = ["NK", "NL", "NM", "NN", "NP", "M1", "M2", "M3"]
+            data_set_name.split('.')[:3])
+        allowed_ids = ['NK', 'NL', 'NM', 'NN', 'NP', 'M1', 'M2', 'M3']
         if platform_id not in allowed_ids:
             raise ReaderError('Improper platform id "%s"!' % platform_id)
 
@@ -741,7 +741,7 @@ def get_telemetry(self):
             space_counts: np.array
 
         """
-        prt_counts = np.mean(self.scans["telemetry"]["PRT"], axis=1)
+        prt_counts = np.mean(self.scans["telemetry"]['PRT'], axis=1)
 
         # getting ICT counts
 
@@ -775,14 +775,14 @@ def get_header_timestamp(self):
             A ValueError if the timestamp is corrupt.
 
         """
-        year = self.head["start_of_data_set_year"]
-        jday = self.head["start_of_data_set_day_of_year"]
-        msec = self.head["start_of_data_set_utc_time_of_day"]
+        year = self.head['start_of_data_set_year']
+        jday = self.head['start_of_data_set_day_of_year']
+        msec = self.head['start_of_data_set_utc_time_of_day']
         try:
             return self.to_datetime(self.to_datetime64(year=year, jday=jday,
                                                        msec=msec))
         except ValueError as err:
-            raise ValueError("Corrupt header timestamp: {0}".format(err))
+            raise ValueError('Corrupt header timestamp: {0}'.format(err))
 
     def _get_times(self):
         """Get the times of the scanlines."""
diff --git a/pygac/lac_klm.py b/pygac/lac_klm.py
index d202f6d2..ccefc3a4 100644
--- a/pygac/lac_klm.py
+++ b/pygac/lac_klm.py
@@ -133,10 +133,10 @@
                      ("frame_sync", ">u2", (6, )),
                      ("id", ">u2", (2, )),
                      ("time_code", ">u2", (4, )),
-                     ("telemetry", [("ramp_calibration", ">u2", (5, )),
-                                    ("PRT", ">u2", (3, )),
-                                    ("ch3_patch_temp", ">u2"),
-                                    ("spare", ">u2"), ]),
+                     ('telemetry', [("ramp_calibration", '>u2', (5, )),
+                                    ("PRT", '>u2', (3, )),
+                                    ("ch3_patch_temp", '>u2'),
+                                    ("spare", '>u2'), ]),
                      ("back_scan", ">u2", (30, )),
                      ("space_data", ">u2", (50, )),
                      ("sync_delta", ">u2"),
diff --git a/pygac/lac_reader.py b/pygac/lac_reader.py
index dd182937..5229d30b 100644
--- a/pygac/lac_reader.py
+++ b/pygac/lac_reader.py
@@ -56,9 +56,9 @@ def _validate_header(cls, header):
         # call super to enter the Method Resolution Order (MRO)
         super(LACReader, cls)._validate_header(header)
         LOG.debug("validate header")
-        data_set_name = header["data_set_name"].decode()
+        data_set_name = header['data_set_name'].decode()
         # split header into parts
         creation_site, transfer_mode, platform_id = (
-            data_set_name.split(".")[:3])
+            data_set_name.split('.')[:3])
         if transfer_mode not in ["LHRR", "HRPT", "FRAC"]:
             raise ReaderError('Improper transfer mode "%s"!' % transfer_mode)
diff --git a/pygac/patmosx_coeff_reader.py b/pygac/patmosx_coeff_reader.py
index b2cadfe3..33c2258b 100644
--- a/pygac/patmosx_coeff_reader.py
+++ b/pygac/patmosx_coeff_reader.py
@@ -37,35 +37,35 @@ class PatmosxReader:
     """Read PATMOS-x coefficient files tarballs."""
     # regular expression with named capturing groups to read an entire patmosx file
     regex = re.compile(
-        r"\s*(?P<sat_name>\w+)[^\n]*\n"
-        r"\s*(?P<solar_3b>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ew_3b>[eE0-9\.-]+)[^\n]*\n"
+        r'\s*(?P<sat_name>\w+)[^\n]*\n'
+        r'\s*(?P<solar_3b>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ew_3b>[eE0-9\.-]+)[^\n]*\n'
         r'\s*(?P<ch3b_Ns>[eE0-9\.-]+),?\s*(?P<ch3b_b0>[eE0-9\.-]+),?\s*(?P<ch3b_b1>[eE0-9\.-]+),?\s*(?P<ch3b_b2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch4_Ns>[eE0-9\.-]+),?\s*(?P<ch4_b0>[eE0-9\.-]+),?\s*(?P<ch4_b1>[eE0-9\.-]+),?\s*(?P<ch4_b2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch5_Ns>[eE0-9\.-]+),?\s*(?P<ch5_b0>[eE0-9\.-]+),?\s*(?P<ch5_b1>[eE0-9\.-]+),?\s*(?P<ch5_b2>[eE0-9\.-]+)[^\n]*\n'  # noqa
-        r"\s*(?P<nu_3b>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a1_3b>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a2_3b>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<nu_4>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a1_4>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a2_4>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<nu_5>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a1_5>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<a2_5>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch1_dark_count>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch2_dark_count>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch3a_dark_count>[eE0-9\.-]+)[^\n]*\n"
-        r"(?:[a-z]+[^\n]*\n)?"
+        r'\s*(?P<nu_3b>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a1_3b>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a2_3b>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<nu_4>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a1_4>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a2_4>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<nu_5>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a1_5>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<a2_5>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch1_dark_count>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch2_dark_count>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch3a_dark_count>[eE0-9\.-]+)[^\n]*\n'
+        r'(?:[a-z]+[^\n]*\n)?'
         r'\s*(?P<ch1_low_gain_S0>[eE0-9\.-]+)\s*(?P<ch1_low_gain_S1>[eE0-9\.-]+)\s*(?P<ch1_low_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch1_high_gain_S0>[eE0-9\.-]+)\s*(?P<ch1_high_gain_S1>[eE0-9\.-]+)\s*(?P<ch1_high_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch2_low_gain_S0>[eE0-9\.-]+)\s*(?P<ch2_low_gain_S1>[eE0-9\.-]+)\s*(?P<ch2_low_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch2_high_gain_S0>[eE0-9\.-]+)\s*(?P<ch2_high_gain_S1>[eE0-9\.-]+)\s*(?P<ch2_high_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch3a_low_gain_S0>[eE0-9\.-]+)\s*(?P<ch3a_low_gain_S1>[eE0-9\.-]+)\s*(?P<ch3a_low_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<ch3a_high_gain_S0>[eE0-9\.-]+)\s*(?P<ch3a_high_gain_S1>[eE0-9\.-]+)\s*(?P<ch3a_high_gain_S2>[eE0-9\.-]+)[^\n]*\n'  # noqa
-        r"\s*(?P<date_of_launch>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch1_gain_switches_count>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch2_gain_switches_count>[eE0-9\.-]+)[^\n]*\n"
-        r"\s*(?P<ch3a_gain_switches_count>[eE0-9\.-]+)[^\n]*\n"
+        r'\s*(?P<date_of_launch>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch1_gain_switches_count>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch2_gain_switches_count>[eE0-9\.-]+)[^\n]*\n'
+        r'\s*(?P<ch3a_gain_switches_count>[eE0-9\.-]+)[^\n]*\n'
         r'\s*(?P<PRT1_0>[eE0-9\.-]+)\,*\s*(?P<PRT1_1>[eE0-9\.-]+)\,*\s*(?P<PRT1_2>[eE0-9\.-]+)\,*\s*(?P<PRT1_3>[eE0-9\.-]+)\,*\s*(?P<PRT1_4>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<PRT2_0>[eE0-9\.-]+)\,*\s*(?P<PRT2_1>[eE0-9\.-]+)\,*\s*(?P<PRT2_2>[eE0-9\.-]+)\,*\s*(?P<PRT2_3>[eE0-9\.-]+)\,*\s*(?P<PRT2_4>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'\s*(?P<PRT3_0>[eE0-9\.-]+)\,*\s*(?P<PRT3_1>[eE0-9\.-]+)\,*\s*(?P<PRT3_2>[eE0-9\.-]+)\,*\s*(?P<PRT3_3>[eE0-9\.-]+)\,*\s*(?P<PRT3_4>[eE0-9\.-]+)[^\n]*\n'  # noqa
@@ -73,8 +73,8 @@ class PatmosxReader:
         r'\s*(?P<PRT_weight_1>[eE0-9\.-]+)\s*(?P<PRT_weight_2>[eE0-9\.-]+)\s*(?P<PRT_weight_3>[eE0-9\.-]+)\s*(?P<PRT_weight_4>[eE0-9\.-]+)[^\n]*\n'  # noqa
         r'(?:\s*(?P<sst_mask_day_0>[eE0-9\.-]+),\s*(?P<sst_mask_day_1>[eE0-9\.-]+),\s*(?P<sst_mask_day_2>[eE0-9\.-]+),\s*(?P<sst_mask_day_3>[eE0-9\.-]+)[^\n]*\n)?'  # noqa
         r'(?:\s*(?P<sst_mask_night_0>[eE0-9\.-]+),\s*(?P<sst_mask_night_1>[eE0-9\.-]+),\s*(?P<sst_mask_night_2>[eE0-9\.-]+),\s*(?P<sst_mask_night_3>[eE0-9\.-]+)[^\n]*\n)?'  # noqa
-        r"(?:\![^v][^\n]*\n)*"
-        r"(?:\!(?P<version>v\w+))?"
+        r'(?:\![^v][^\n]*\n)*'
+        r'(?:\!(?P<version>v\w+))?'
     )
 
     def __init__(self, tarball):
@@ -115,9 +115,9 @@ class Translator:
     sat_names.update({"n{0:02d}".format(i): "noaa{0}".format(i) for i in range(6,20)})
     description = {
         "visible": {
-            "channels": ["1", "2", "3a"],
+            "channels": ['1', '2', '3a'],
             "coefficients": {
-                "dark_count": "instrument counts under dark conditions []",
+                'dark_count': "instrument counts under dark conditions []",
                 "gain_switch": "dual-gain switch count, set to 'null' for single-gain instruments []",
                 "s0": "single-gain calibration slope at launch date [%]",
                 "s1": "linear single-gain calibration slope parameter [% years^{-1}]",
@@ -127,9 +127,9 @@ class Translator:
             "method": 'Heidinger, A.K., W.C. Straka III, C.C. Molling, J.T. Sullivan, and X. Wu, 2010: Deriving an inter-sensor consistent calibration for the AVHRR solar reflectance data record. International Journal of Remote Sensing, 31:6493-6517'  # noqa
         },
         "thermal": {
-            "channels": ["3b", "4", "5"],
+            "channels": ['3b', '4', '5'],
             "coefficients": {
-                "centroid_wavenumber": "centroid wavenumber [cm^{-1}]",
+                'centroid_wavenumber': "centroid wavenumber [cm^{-1}]",
                 "b0": "constant non-linear radiance correction coefficient [mW m^{-2} sr cm^{-1}]",
                 "b1": "linear non-linear radiance correction coefficient []",
                 "b2": "quadratic non-linear radiance correction coefficient [(mW^{-1} m^2 sr^{-1} cm)]",
@@ -158,34 +158,34 @@ def convert(cls, patmosx_sat_coeffs):
         pygac_sat_coeffs = {}
         # visible calibration
         for ch in ("1", "2", "3a"):
-            s0l = patmosx_sat_coeffs["ch{0}_low_gain_S0".format(ch)]
-            s0h = patmosx_sat_coeffs["ch{0}_high_gain_S0".format(ch)]
+            s0l = patmosx_sat_coeffs['ch{0}_low_gain_S0'.format(ch)]
+            s0h = patmosx_sat_coeffs['ch{0}_high_gain_S0'.format(ch)]
             if s0l == s0h:
                 gain_switch = None
                 s0 = s0l
             else:
-                gain_switch = patmosx_sat_coeffs["ch{0}_gain_switches_count".format(ch)]
+                gain_switch = patmosx_sat_coeffs['ch{0}_gain_switches_count'.format(ch)]
                 s0 = cls.find_s0(s0l, s0h, ch)
             pygac_sat_coeffs["channel_{0}".format(ch)] = {
-                "dark_count": float(patmosx_sat_coeffs["ch{0}_dark_count".format(ch)]),
+                "dark_count": float(patmosx_sat_coeffs['ch{0}_dark_count'.format(ch)]),
                 "gain_switch": gain_switch,
                 "s0": s0,
-                "s1": patmosx_sat_coeffs["ch{0}_high_gain_S1".format(ch)],
-                "s2": patmosx_sat_coeffs["ch{0}_high_gain_S2".format(ch)]
+                "s1": patmosx_sat_coeffs['ch{0}_high_gain_S1'.format(ch)],
+                "s2": patmosx_sat_coeffs['ch{0}_high_gain_S2'.format(ch)]
             }
-        date_of_launch = cls.float2date(patmosx_sat_coeffs["date_of_launch"])
-        pygac_sat_coeffs["date_of_launch"] = date_of_launch.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
+        date_of_launch = cls.float2date(patmosx_sat_coeffs['date_of_launch'])
+        pygac_sat_coeffs['date_of_launch'] = date_of_launch.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
         # thermal channels
         for ch in ("3b", "4", "5"):
             pygac_sat_coeffs["channel_{0}".format(ch)] = {
-                "b0": patmosx_sat_coeffs["ch{0}_b0".format(ch)],
-                "b1": patmosx_sat_coeffs["ch{0}_b1".format(ch)],
-                "b2": patmosx_sat_coeffs["ch{0}_b2".format(ch)],
-                "centroid_wavenumber": patmosx_sat_coeffs["nu_{0}".format(ch)],
-                "space_radiance": patmosx_sat_coeffs["ch{0}_Ns".format(ch)],
-                "to_eff_blackbody_intercept": (-patmosx_sat_coeffs["a1_{0}".format(ch)]
-                                                / patmosx_sat_coeffs["a2_{0}".format(ch)]),
-                "to_eff_blackbody_slope": 1/patmosx_sat_coeffs["a2_{0}".format(ch)]
+                "b0": patmosx_sat_coeffs['ch{0}_b0'.format(ch)],
+                "b1": patmosx_sat_coeffs['ch{0}_b1'.format(ch)],
+                "b2": patmosx_sat_coeffs['ch{0}_b2'.format(ch)],
+                "centroid_wavenumber": patmosx_sat_coeffs['nu_{0}'.format(ch)],
+                "space_radiance": patmosx_sat_coeffs['ch{0}_Ns'.format(ch)],
+                "to_eff_blackbody_intercept": (-patmosx_sat_coeffs['a1_{0}'.format(ch)]
+                                                / patmosx_sat_coeffs['a2_{0}'.format(ch)]),
+                "to_eff_blackbody_slope": 1/patmosx_sat_coeffs['a2_{0}'.format(ch)]
             }
         for t in range(1, 5):
             pygac_sat_coeffs["thermometer_{0}".format(t)] = {
@@ -209,7 +209,7 @@ def find_s0(s0_low, s0_high, ch):
         if s0_low == s0_high:
             # single gain case
             return s0_low
-        if ch == "3a":
+        if ch == '3a':
             g_low, g_high = 0.25, 1.75
         else:
             g_low, g_high = 0.5, 1.5
@@ -249,32 +249,32 @@ def float2date(date_float):
 
     def save(self, filepath):
         """Save coefficients as PyGAC json file."""
-        with open(filepath, mode="w") as json_file:
+        with open(filepath, mode='w') as json_file:
             json.dump(self.coeffs, json_file, indent=4, sort_keys=True)
 
 
 def main():
     """The main function."""
     parser = argparse.ArgumentParser(description=__doc__)
-    parser.add_argument("tarball", type=str, help="path to PATMOS-x coefficients tarball")
-    parser.add_argument("-o", "--output", type=str, metavar="JSON",
+    parser.add_argument('tarball', type=str, help='path to PATMOS-x coefficients tarball')
+    parser.add_argument('-o', '--output', type=str, metavar="JSON",
                         help='path to PyGAC json file, defaults to tarball path with suffix ".json"')
-    parser.add_argument("-v", "--verbose", action="store_true", help="explain what is being done")
+    parser.add_argument('-v', '--verbose', action='store_true', help='explain what is being done')
     args = parser.parse_args()
     if args.verbose:
         loglevel = logging.INFO
     else:
         loglevel = logging.WARNING
-    logging.basicConfig(level=loglevel, format="[%(asctime)s] %(message)s")
+    logging.basicConfig(level=loglevel, format='[%(asctime)s] %(message)s')
     tarball = pathlib.Path(args.tarball)
     logging.info('Read PATMOS-x tarball "%s".', tarball)
     patmosx_coeffs = PatmosxReader(tarball)
-    logging.info("Translate PATMOS-x coefficients to PyGAC format.")
+    logging.info('Translate PATMOS-x coefficients to PyGAC format.')
     pygac_coeffs = Translator(patmosx_coeffs)
     output = args.output or tarball.with_suffix(".json")
     logging.info('Write PyGAC calibration json file "%s".', output)
     pygac_coeffs.save(output)
-    logging.info("Done!")
+    logging.info('Done!')
 
 if __name__ == "__main__":
     main()
diff --git a/pygac/pod_reader.py b/pygac/pod_reader.py
index e8c90783..c0e310c2 100644
--- a/pygac/pod_reader.py
+++ b/pygac/pod_reader.py
@@ -198,44 +198,44 @@ class POD_QualityIndicator(IntFlag):
                     ("pitch_fixed_error_correction", ">i2")])
 
 # archive header
-tbm_header = np.dtype([("fill", "S30"),
-                       ("data_set_name", "S44"),
-                       ("select_flag", "S1"),
-                       ("beginning_latitude", "S3"),
-                       ("ending_latitude", "S3"),
-                       ("beginning_longitude", "S4"),
-                       ("ending_longitude", "S4"),
-                       ("start_hour", "S2"),
-                       ("start_minute", "S2"),
-                       ("number_of_minutes", "S3"),
-                       ("appended_data_flag", "S1"),
-                       ("channel_select_flag", "S1", (20, )),
-                       ("sensor_data_word_size", "S2"),
-                       ("fill2", "S3")])
+tbm_header = np.dtype([('fill', 'S30'),
+                       ('data_set_name', 'S44'),
+                       ('select_flag', 'S1'),
+                       ('beginning_latitude', 'S3'),
+                       ('ending_latitude', 'S3'),
+                       ('beginning_longitude', 'S4'),
+                       ('ending_longitude', 'S4'),
+                       ('start_hour', 'S2'),
+                       ('start_minute', 'S2'),
+                       ('number_of_minutes', 'S3'),
+                       ('appended_data_flag', 'S1'),
+                       ('channel_select_flag', 'S1', (20, )),
+                       ('sensor_data_word_size', 'S2'),
+                       ('fill2', 'S3')])
 
 
 class PODReader(Reader):
     """The POD reader."""
 
-    spacecrafts_orbital = {25: "tiros n",
-                           2: "noaa 6",
-                           4: "noaa 7",
-                           6: "noaa 8",
-                           7: "noaa 9",
-                           8: "noaa 10",
-                           1: "noaa 11",
-                           5: "noaa 12",
-                           3: "noaa 14",
+    spacecrafts_orbital = {25: 'tiros n',
+                           2: 'noaa 6',
+                           4: 'noaa 7',
+                           6: 'noaa 8',
+                           7: 'noaa 9',
+                           8: 'noaa 10',
+                           1: 'noaa 11',
+                           5: 'noaa 12',
+                           3: 'noaa 14',
                            }
-    spacecraft_names = {25: "tirosn",
-                        2: "noaa6",
-                        4: "noaa7",
-                        6: "noaa8",
-                        7: "noaa9",
-                        8: "noaa10",
-                        1: "noaa11",
-                        5: "noaa12",
-                        3: "noaa14",
+    spacecraft_names = {25: 'tirosn',
+                        2: 'noaa6',
+                        4: 'noaa7',
+                        6: 'noaa8',
+                        7: 'noaa9',
+                        8: 'noaa10',
+                        1: 'noaa11',
+                        5: 'noaa12',
+                        3: 'noaa14',
                         }
 
     tsm_affected_intervals = TSM_AFFECTED_INTERVALS_POD
@@ -275,7 +275,7 @@ def read(self, filename, fileobj=None):
 
         """
         self.filename = filename
-        LOG.info("Reading %s", self.filename)
+        LOG.info('Reading %s', self.filename)
         # choose the right header depending on the date
         with file_opener(fileobj or filename) as fd_:
             self.tbm_head, self.head = self.read_header(
@@ -382,12 +382,12 @@ def _validate_header(cls, header):
         # call super to enter the Method Resolution Order (MRO)
         super(PODReader, cls)._validate_header(header)
         LOG.debug("validate header")
-        data_set_name = header["data_set_name"].decode()
+        data_set_name = header['data_set_name'].decode()
         # split header into parts
         creation_site, transfer_mode, platform_id = (
-            data_set_name.split(".")[:3])
-        allowed_ids = ["TN", "NA", "NB", "NC", "ND", "NE", "NF", "NG",
-                       "NH", "NI", "NJ"]
+            data_set_name.split('.')[:3])
+        allowed_ids = ['TN', 'NA', 'NB', 'NC', 'ND', 'NE', 'NF', 'NG',
+                       'NH', 'NI', 'NJ']
         if platform_id not in allowed_ids:
             raise ReaderError('Improper platform id "%s"!' % platform_id)
 
@@ -406,7 +406,7 @@ def get_header_timestamp(self):
             return self.to_datetime(self.to_datetime64(year=year, jday=jday,
                                                        msec=msec))
         except ValueError as err:
-            raise ValueError("Corrupt header timestamp: {0}".format(err))
+            raise ValueError('Corrupt header timestamp: {0}'.format(err))
 
     @staticmethod
     def decode_timestamps(encoded):
@@ -430,7 +430,7 @@ def decode_timestamps(encoded):
             enc1 = encoded[:, 1]
             enc2 = encoded[:, 2]
         else:
-            raise ValueError("Invalid timestamp dimension")
+            raise ValueError('Invalid timestamp dimension')
 
         year = enc0 >> 9
         year = np.where(year > 75, year + 1900, year + 2000)
@@ -478,7 +478,7 @@ def _adjust_clock_drift(self):
                      self.spacecraft_name)
             return
 
-        error_utcs = np.array(error_utcs, dtype="datetime64[ms]")
+        error_utcs = np.array(error_utcs, dtype='datetime64[ms]')
         # interpolate to get the clock offsets at the scan line utcs
         # the clock_error is given in seconds, so offsets are in seconds, too.
         offsets = np.interp(self.utcs.astype(np.uint64),
@@ -511,7 +511,7 @@ def _adjust_clock_drift(self):
         try:
             missed_lons, missed_lats = self._compute_missing_lonlat(missed_utcs)
         except NoTLEData as err:
-            LOG.warning("Cannot perform clock drift correction: %s", str(err))
+            LOG.warning('Cannot perform clock drift correction: %s', str(err))
             return
 
         # create arrays of lons and lats for interpolation. The locations
@@ -539,7 +539,7 @@ def _adjust_clock_drift(self):
         # set corrected values
         self.lons = slerp_res[:, :, 0]
         self.lats = slerp_res[:, :, 1]
-        self.utcs -= (offsets * 1000).astype("timedelta64[ms]")
+        self.utcs -= (offsets * 1000).astype('timedelta64[ms]')
 
         toc = datetime.datetime.now()
         LOG.debug("clock drift adjustment took %s", str(toc - tic))
diff --git a/pygac/reader.py b/pygac/reader.py
index 381305ca..6aa4b3aa 100644
--- a/pygac/reader.py
+++ b/pygac/reader.py
@@ -48,29 +48,29 @@
 # rpy values from
 # here:http://yyy.rsmas.miami.edu/groups/rrsl/pathfinder/Processing/proc_app_a.html
 rpy_coeffs = {
-    "noaa7": {"roll": 0.000,
-              "pitch": 0.000,
-              "yaw": 0.000,
+    'noaa7': {'roll': 0.000,
+              'pitch': 0.000,
+              'yaw': 0.000,
               },
-    "noaa9": {"roll": 0.000,
-              "pitch": 0.0025,
-              "yaw": 0.000,
+    'noaa9': {'roll': 0.000,
+              'pitch': 0.0025,
+              'yaw': 0.000,
               },
-    "noaa10": {"roll": 0.000,
-               "pitch": 0.000,
-               "yaw": 0.000,
+    'noaa10': {'roll': 0.000,
+               'pitch': 0.000,
+               'yaw': 0.000,
                },
-    "noaa11": {"roll": -0.0019,
-               "pitch": -0.0037,
-               "yaw": 0.000,
+    'noaa11': {'roll': -0.0019,
+               'pitch': -0.0037,
+               'yaw': 0.000,
                },
-    "noaa12": {"roll": 0.000,
-               "pitch": 0.000,
-               "yaw": 0.000,
+    'noaa12': {'roll': 0.000,
+               'pitch': 0.000,
+               'yaw': 0.000,
                },
-    "noaa14": {"roll": 0.000,
-               "pitch": 0.000,
-               "yaw": 0.000,
+    'noaa14': {'roll': 0.000,
+               'pitch': 0.000,
+               'yaw': 0.000,
                }}
 
 
@@ -93,7 +93,7 @@ class Reader(ABC):
 
     # data set header format, see _validate_header for more details
     data_set_pattern = re.compile(
-        r"\w{3}\.\w{4}\.\w{2}.D\d{5}\.S\d{4}\.E\d{4}\.B\d{7}\.\w{2}")
+        r'\w{3}\.\w{4}\.\w{2}.D\d{5}\.S\d{4}\.E\d{4}\.B\d{7}\.\w{2}')
 
     def __init__(self, interpolate_coords=True, adjust_clock_drift=True,
                  tle_dir=None, tle_name=None, tle_thresh=7, creation_site=None,
@@ -123,7 +123,7 @@ def __init__(self, interpolate_coords=True, adjust_clock_drift=True,
         self.tle_dir = tle_dir
         self.tle_name = tle_name
         self.tle_thresh = tle_thresh
-        self.creation_site = (creation_site or "NSS").encode("utf-8")
+        self.creation_site = (creation_site or 'NSS').encode('utf-8')
         self.header_date = header_date
         self.head = None
         self.scans = None
@@ -211,7 +211,7 @@ def _correct_data_set_name(cls, header, filename):
             filename (str): path to file
         """
         filename = str(filename)
-        data_set_name = header["data_set_name"]
+        data_set_name = header['data_set_name']
         try:
             header["data_set_name"] = cls._decode_data_set_name(data_set_name)
         except DecodingError:
@@ -221,10 +221,10 @@ def _correct_data_set_name(cls, header, filename):
             if match:
                 data_set_name = match.group()
                 LOG.debug(f"Set data_set_name, to filename {data_set_name}")
-                header["data_set_name"] = data_set_name.encode()
+                header['data_set_name'] = data_set_name.encode()
             else:
                 LOG.debug(f"header['data_set_name']={header['data_set_name']}; filename='{filename}'")
-                raise ReaderError("Cannot determine data_set_name!")
+                raise ReaderError('Cannot determine data_set_name!')
         return header
 
     @classmethod
@@ -243,8 +243,8 @@ def _decode_data_set_name(cls, data_set_name):
     def _decode_data_set_name_for_encoding(cls, data_set_name, encoding):
         data_set_name = data_set_name.decode(encoding, errors="ignore")
         if not cls.data_set_pattern.match(data_set_name):
-            raise DecodingError(f"The data_set_name in header {data_set_name} "
-                                f"does not seem correct using encoding {encoding}.")
+            raise DecodingError(f'The data_set_name in header {data_set_name} '
+                                f'does not seem correct using encoding {encoding}.')
         else:
             data_set_name = data_set_name.encode()
         return data_set_name
@@ -282,10 +282,10 @@ def _validate_header(cls, header):
         # second use case "diamond diagrams".
         # Check if the data set name matches the pattern
         LOG.debug("validate header")
-        data_set_name = header["data_set_name"].decode(errors="ignore")
+        data_set_name = header['data_set_name'].decode(errors='ignore')
         if not cls.data_set_pattern.match(data_set_name):
-            raise ReaderError("Data set name %s does not match!"
-                              % header["data_set_name"])
+            raise ReaderError('Data set name %s does not match!'
+                              % header['data_set_name'])
 
     def _read_scanlines(self, buffer, count):
         """Read the scanlines from the given buffer.
@@ -476,9 +476,9 @@ def to_datetime64(year, jday, msec):
             numpy.datetime64: Converted timestamps
 
         """
-        return (year.astype(str).astype("datetime64[Y]")
-                + (jday - 1).astype("timedelta64[D]")
-                + msec.astype("timedelta64[ms]"))
+        return (year.astype(str).astype('datetime64[Y]')
+                + (jday - 1).astype('timedelta64[D]')
+                + msec.astype('timedelta64[ms]'))
 
     @staticmethod
     def to_datetime(datetime64):
@@ -518,17 +518,17 @@ def update_meta_data(self):
         """Add some meta data to the meta_data dicitonary."""
         meta_data = self.meta_data
         self._update_meta_data_object(meta_data)
-        if "gac_header" not in meta_data:
-            meta_data["gac_header"] = self.head.copy()
+        if 'gac_header' not in meta_data:
+            meta_data['gac_header'] = self.head.copy()
 
     def _update_meta_data_object(self, meta_data):
-        if "sun_earth_distance_correction_factor" not in meta_data:
-            meta_data["sun_earth_distance_correction_factor"] = (
+        if 'sun_earth_distance_correction_factor' not in meta_data:
+            meta_data['sun_earth_distance_correction_factor'] = (
                 self.get_sun_earth_distance_correction())
-        if "midnight_scanline" not in meta_data:
-            meta_data["midnight_scanline"] = self.get_midnight_scanline()
-        if "missing_scanlines" not in meta_data:
-            meta_data["missing_scanlines"] = self.get_miss_lines()
+        if 'midnight_scanline' not in meta_data:
+            meta_data['midnight_scanline'] = self.get_midnight_scanline()
+        if 'missing_scanlines' not in meta_data:
+            meta_data['missing_scanlines'] = self.get_miss_lines()
 
     def read_as_dataset(self, file_to_read):
         self.read(file_to_read)
@@ -629,7 +629,7 @@ def get_calibrated_dataset(self):
 
         # Mask pixels affected by scan motor issue
         if self.is_tsm_affected():
-            LOG.info("Correcting for temporary scan motor issue")
+            LOG.info('Correcting for temporary scan motor issue')
             self.mask_tsm_pixels(calibrated_ds)
         return calibrated_ds
 
@@ -739,13 +739,13 @@ def tle2datetime64(times):
         times = np.where(times > 50000, times + 1900000, times + 2000000)
 
         # Convert float to datetime64
-        doys = (times % 1000).astype("int") - 1
-        years = (times // 1000).astype("int")
+        doys = (times % 1000).astype('int') - 1
+        years = (times // 1000).astype('int')
         msecs = np.rint(24 * 3600 * 1000 * (times % 1))
         times64 = (
-            years - 1970).astype("datetime64[Y]").astype("datetime64[ms]")
-        times64 += doys.astype("timedelta64[D]")
-        times64 += msecs.astype("timedelta64[ms]")
+            years - 1970).astype('datetime64[Y]').astype('datetime64[ms]')
+        times64 += doys.astype('timedelta64[D]')
+        times64 += msecs.astype('timedelta64[ms]')
 
         return times64
 
@@ -758,13 +758,13 @@ def get_tle_file(self):
             raise RuntimeError("TLE name not specified!")
         values = {"satname": self.spacecraft_name, }
         tle_filename = os.path.join(tle_dir, tle_name % values)
-        LOG.info("TLE filename = " + str(tle_filename))
+        LOG.info('TLE filename = ' + str(tle_filename))
 
         return tle_filename
 
     def read_tle_file(self, tle_filename):
         """Read TLE file."""
-        with open(tle_filename, "r") as fp_:
+        with open(tle_filename, 'r') as fp_:
             return fp_.readlines()
 
     def get_tle_lines(self):
@@ -797,7 +797,7 @@ def get_tle_lines(self):
             iindex -= 1
 
         # Make sure the TLE we found is within the threshold
-        delta_days = abs(sdate - dates[iindex]) / np.timedelta64(1, "D")
+        delta_days = abs(sdate - dates[iindex]) / np.timedelta64(1, 'D')
         if delta_days > self.tle_thresh:
             raise NoTLEData(
                 "Can't find tle data for %s within +/- %d days around %s" %
@@ -826,8 +826,8 @@ def get_sat_angles(self):
             return self._get_sat_angles_with_tle()
         except NoTLEData:
             LOG.warning(
-                "No TLE data available. Falling back to approximate "
-                "calculation of satellite angles."
+                'No TLE data available. Falling back to approximate '
+                'calculation of satellite angles.'
             )
             return self._get_sat_angles_without_tle()
 
@@ -842,7 +842,7 @@ def _get_sat_angles_with_tle(self):
     def _get_sat_angles_without_tle(self):
         """Get satellite angles using lat/lon from data to approximate satellite postition instead of TLE."""
         from pyorbital.orbital import get_observer_look as get_observer_look_no_tle
-        LOG.warning("Approximating satellite height to 850km (TIROS-N OSCAR)!")
+        LOG.warning('Approximating satellite height to 850km (TIROS-N OSCAR)!')
         sat_alt = 850.0  # km  TIROS-N OSCAR
         mid_column = int(0.5*self.lons.shape[1])
         sat_azi, sat_elev = get_observer_look_no_tle(
@@ -853,7 +853,7 @@ def _get_sat_angles_without_tle(self):
             self.lons, self.lats, 0)
         # Sometimes (pyorbital <= 1.6.1) the get_observer_look_not_tle returns nodata instead of 90.
         # Problem solved with https://github.com/pytroll/pyorbital/pull/77
-        if Version(pyorbital.__version__) <= Version("1.6.1"):
+        if Version(pyorbital.__version__) <= Version('1.6.1'):
             sat_elev[:, mid_column] = 90
         return sat_azi, sat_elev
 
@@ -979,8 +979,8 @@ def correct_scan_line_numbers(self):
 
         """
         along_track = np.arange(1, len(self.scans["scan_line_number"])+1)
-        results = {"along_track": along_track,
-                   "n_orig": self.scans["scan_line_number"].copy()}
+        results = {'along_track': along_track,
+                   'n_orig': self.scans['scan_line_number'].copy()}
 
         # Remove scanlines whose scanline number is outside the valid range
         within_range = np.logical_and(self.scans["scan_line_number"] < self.max_scanlines,
@@ -1023,14 +1023,14 @@ def correct_scan_line_numbers(self):
                 thresh = max(500, med_nz_diffs + 3*mad_nz_diffs)
         self.scans = self.scans[diffs <= thresh]
 
-        LOG.debug("Removed %s scanline(s) with corrupt scanline numbers",
+        LOG.debug('Removed %s scanline(s) with corrupt scanline numbers',
                   str(len(along_track) - len(self.scans)))
 
-        results.update({"n_corr": self.scans["scan_line_number"],
-                        "within_range": within_range,
-                        "diffs": diffs,
-                        "thresh": thresh,
-                        "nz_diffs": nz_diffs})
+        results.update({'n_corr': self.scans['scan_line_number'],
+                        'within_range': within_range,
+                        'diffs': diffs,
+                        'thresh': thresh,
+                        'nz_diffs': nz_diffs})
         return results
 
     def correct_times_thresh(self, max_diff_from_t0_head=6*60*1000,
@@ -1081,11 +1081,11 @@ def correct_times_thresh(self, max_diff_from_t0_head=6*60*1000,
 
         # Check whether scanline number increases monotonically
         nums = self.scans["scan_line_number"]
-        results.update({"t": self.utcs.copy(), "n": nums})
+        results.update({'t': self.utcs.copy(), 'n': nums})
         if np.any(np.diff(nums) < 0):
             LOG.error("Cannot perform timestamp correction. Scanline number "
                       "does not increase monotonically.")
-            results["fail_reason"] = "Scanline number jumps backwards"
+            results['fail_reason'] = "Scanline number jumps backwards"
             return results
 
         # Convert time to milliseconds since 1970-01-01
@@ -1116,14 +1116,14 @@ def correct_times_thresh(self, max_diff_from_t0_head=6*60*1000,
         #    we do not have reliable information and cannot proceed.
         near_t0_head = np.where(
             np.fabs(offsets - t0_head) <= max_diff_from_t0_head)[0]
-        results.update({"offsets": offsets,
-                        "t0_head": t0_head,
-                        "max_diff_from_t0_head": max_diff_from_t0_head})
+        results.update({'offsets': offsets,
+                        't0_head': t0_head,
+                        'max_diff_from_t0_head': max_diff_from_t0_head})
         if near_t0_head.size / float(nums.size) >= min_frac_near_t0_head:
             t0 = np.median(offsets[near_t0_head])
         else:
             LOG.error("Timestamp mismatch. Cannot perform correction.")
-            results["fail_reason"] = "Timestamp mismatch"
+            results['fail_reason'] = "Timestamp mismatch"
             return results
 
         # Add estimated offset to the ideal timestamps
@@ -1135,7 +1135,7 @@ def correct_times_thresh(self, max_diff_from_t0_head=6*60*1000,
         self.utcs[corrupt_lines] = tn[corrupt_lines].astype(dt64_msec)
         LOG.debug("Corrected %s timestamp(s)", str(len(corrupt_lines[0])))
 
-        results.update({"tn": tn, "tcorr": self.utcs, "t0": t0})
+        results.update({'tn': tn, 'tcorr': self.utcs, 't0': t0})
         return results
 
     @property
@@ -1181,13 +1181,13 @@ def get_midnight_scanline(self):
 
         """
         self.get_times()
-        d0 = np.datetime64(datetime.date(1970, 1, 1), "D")
-        days = (self.utcs.astype("datetime64[D]") - d0).astype(int)
+        d0 = np.datetime64(datetime.date(1970, 1, 1), 'D')
+        days = (self.utcs.astype('datetime64[D]') - d0).astype(int)
         incr = np.where(np.diff(days) == 1)[0]
         if len(incr) != 1:
             if len(incr) > 1:
-                LOG.warning("Unable to determine midnight scanline: "
-                            "UTC date increases more than once. ")
+                LOG.warning('Unable to determine midnight scanline: '
+                            'UTC date increases more than once. ')
             return None
         else:
             return incr[0]
@@ -1203,8 +1203,8 @@ def get_miss_lines(self):
         """
         # Compare scanline number against the ideal case (1, 2, 3, ...) and
         # find the missing line numbers.
-        ideal = set(range(1, self.scans["scan_line_number"][-1] + 1))
-        missing = sorted(ideal.difference(set(self.scans["scan_line_number"])))
+        ideal = set(range(1, self.scans['scan_line_number'][-1] + 1))
+        missing = sorted(ideal.difference(set(self.scans['scan_line_number'])))
         return np.array(missing, dtype=int)
 
     def mask_tsm_pixels(self, ds):
@@ -1254,7 +1254,7 @@ def inherit_doc(cls):
         if isinstance(func, types.FunctionType) and not func.__doc__:
             for parent in cls.__bases__:
                 parfunc = getattr(parent, name, None)
-                if parfunc and getattr(parfunc, "__doc__", None):
+                if parfunc and getattr(parfunc, '__doc__', None):
                     func.__doc__ = parfunc.__doc__
                     break
     return cls
diff --git a/pygac/runner.py b/pygac/runner.py
index 78e1d4d0..7fd72140 100644
--- a/pygac/runner.py
+++ b/pygac/runner.py
@@ -86,15 +86,15 @@ def process_file(filename, start_line, end_line, fileobj=None):
 
     # reader specific values
     config = get_config()
-    tle_dir = config.get("tle", "tledir", raw=True)
-    tle_name = config.get("tle", "tlename", raw=True)
-    coeffs_file = config.get("calibration", "coeffs_file", fallback="")
+    tle_dir = config.get('tle', 'tledir', raw=True)
+    tle_name = config.get('tle', 'tlename', raw=True)
+    coeffs_file = config.get("calibration", "coeffs_file", fallback='')
     # output specific values
-    output_dir = config.get("output", "output_dir", raw=True)
-    output_file_prefix = config.get("output", "output_file_prefix", raw=True)
-    avhrr_dir = os.environ.get("SM_AVHRR_DIR")
-    qual_dir = os.environ.get("SM_AVHRR_DIR")
-    sunsatangles_dir = os.environ.get("SM_SUNSATANGLES_DIR")
+    output_dir = config.get('output', 'output_dir', raw=True)
+    output_file_prefix = config.get('output', 'output_file_prefix', raw=True)
+    avhrr_dir = os.environ.get('SM_AVHRR_DIR')
+    qual_dir = os.environ.get('SM_AVHRR_DIR')
+    sunsatangles_dir = os.environ.get('SM_SUNSATANGLES_DIR')
 
     # Keep the file open while searching for the reader class and later
     # creation of the instance.
diff --git a/pygac/tests/test_io.py b/pygac/tests/test_io.py
index c859c74b..df3a4cb7 100644
--- a/pygac/tests/test_io.py
+++ b/pygac/tests/test_io.py
@@ -44,14 +44,14 @@ def test_strip_invalid_lat(self):
 
     def test_update_scanline(self):
         """Test updating the scanlines."""
-        test_data = [{"new_start_line": 100, "new_end_line": 200,
-                      "scanline": 110, "scanline_exp": 10},
-                     {"new_start_line": 100, "new_end_line": 200,
-                      "scanline": 90, "scanline_exp": None},
-                     {"new_start_line": 100, "new_end_line": 200,
-                      "scanline": 210, "scanline_exp": None}]
+        test_data = [{'new_start_line': 100, 'new_end_line': 200,
+                      'scanline': 110, 'scanline_exp': 10},
+                     {'new_start_line': 100, 'new_end_line': 200,
+                      'scanline': 90, 'scanline_exp': None},
+                     {'new_start_line': 100, 'new_end_line': 200,
+                      'scanline': 210, 'scanline_exp': None}]
         for t in test_data:
-            scanline_exp = t.pop("scanline_exp")
+            scanline_exp = t.pop('scanline_exp')
             scanline = utils._update_scanline(**t)
             self.assertEqual(scanline, scanline_exp)
 
@@ -59,12 +59,12 @@ def test_update_missing_scanlines(self):
         """Test updating the missing scanlines."""
         qual_flags = np.array([[1, 2, 4, 5, 6, 8, 9, 11, 12]]).transpose()
         miss_lines = np.array([3, 7, 10])
-        test_data = [{"start_line": 0, "end_line": 8,
-                      "miss_lines_exp": [3, 7, 10]},
-                     {"start_line": 3, "end_line": 6,
-                      "miss_lines_exp": [1, 2, 3, 4, 7, 10, 11, 12]}]
+        test_data = [{'start_line': 0, 'end_line': 8,
+                      'miss_lines_exp': [3, 7, 10]},
+                     {'start_line': 3, 'end_line': 6,
+                      'miss_lines_exp': [1, 2, 3, 4, 7, 10, 11, 12]}]
         for t in test_data:
-            miss_lines_exp = t.pop("miss_lines_exp")
+            miss_lines_exp = t.pop('miss_lines_exp')
             miss_lines = utils._update_missing_scanlines(
                 miss_lines=miss_lines, qual_flags=qual_flags, **t)
             numpy.testing.assert_array_equal(miss_lines, miss_lines_exp)
@@ -185,10 +185,10 @@ def test_check_user_scanlines(self):
         self.assertRaises(ValueError, gac_io.check_user_scanlines,
                           110, 120, None, None, 100)
 
-    @mock.patch("pygac.gac_io.strip_invalid_lat")
-    @mock.patch("pygac.gac_io.avhrrGAC_io")
-    @mock.patch("pygac.gac_io.slice_channel")
-    @mock.patch("pygac.gac_io.check_user_scanlines")
+    @mock.patch('pygac.gac_io.strip_invalid_lat')
+    @mock.patch('pygac.gac_io.avhrrGAC_io')
+    @mock.patch('pygac.gac_io.slice_channel')
+    @mock.patch('pygac.gac_io.check_user_scanlines')
     def test_save_gac(self, check_user_scanlines, slice_channel, avhrr_gac_io,
                       strip_invalid_lat):
         """Test saving."""
@@ -218,13 +218,13 @@ def test_save_gac(self, check_user_scanlines, slice_channel, avhrr_gac_io,
             qual_dir=mm,
             sunsatangles_dir=mm
         )
-        slice_channel.return_value = mm, "miss", "midnight"
+        slice_channel.return_value = mm, 'miss', 'midnight'
         strip_invalid_lat.return_value = 0, 0
-        check_user_scanlines.return_value = "start", "end"
+        check_user_scanlines.return_value = 'start', 'end'
 
         gac_io.save_gac(start_line=0, end_line=0, **kwargs)
         slice_channel.assert_called_with(mock.ANY,
-                                         start_line="start", end_line="end",
+                                         start_line='start', end_line='end',
                                          first_valid_lat=mock.ANY,
                                          last_valid_lat=mock.ANY
                                          )
@@ -255,8 +255,8 @@ def test_save_gac(self, check_user_scanlines, slice_channel, avhrr_gac_io,
             mock.ANY,
             mock.ANY,
             mock.ANY,
-            "midnight",
-            "miss",
+            'midnight',
+            'miss',
             mock.ANY,
             mock.ANY,
             mock.ANY,
diff --git a/pygac/tests/test_klm.py b/pygac/tests/test_klm.py
index cc771f04..0b476808 100644
--- a/pygac/tests/test_klm.py
+++ b/pygac/tests/test_klm.py
@@ -60,24 +60,24 @@ def test_get_lonlat(self):
     def test_get_header_timestamp(self):
         """Test readout of header timestamp."""
         self.reader.head = {
-            "start_of_data_set_year": np.array([2019]),
-            "start_of_data_set_day_of_year": np.array([123]),
-            "start_of_data_set_utc_time_of_day": np.array([123456])
+            'start_of_data_set_year': np.array([2019]),
+            'start_of_data_set_day_of_year': np.array([123]),
+            'start_of_data_set_utc_time_of_day': np.array([123456])
         }
         time = self.reader.get_header_timestamp()
         assert time == dt.datetime(2019, 5, 3, 0, 2, 3, 456000)
 
     def test_get_times(self):
         """Test readout of scanline timestamps."""
-        self.reader.scans = {"scan_line_year": 1,
-                             "scan_line_day_of_year": 2,
-                             "scan_line_utc_time_of_day": 3}
+        self.reader.scans = {'scan_line_year': 1,
+                             'scan_line_day_of_year': 2,
+                             'scan_line_utc_time_of_day': 3}
         assert self.reader._get_times() == (1, 2, 3)
 
     def test_get_ch3_switch(self):
         """Test channel 3 identification."""
         self.reader.scans = {
-            "scan_line_bit_field": np.array([1, 2, 3, 4, 5, 6])}
+            'scan_line_bit_field': np.array([1, 2, 3, 4, 5, 6])}
         switch_exp = np.array([1, 2, 3, 0, 1, 2])
         numpy.testing.assert_array_equal(
             self.reader.get_ch3_switch(), switch_exp)
@@ -85,7 +85,7 @@ def test_get_ch3_switch(self):
     def test_postproc(self):
         """Test KLM specific postprocessing."""
         self.reader.scans = {
-            "scan_line_bit_field": np.array([0, 1, 2])}
+            'scan_line_bit_field': np.array([0, 1, 2])}
         channels = np.array([[[1., 2., 3., 4.],
                               [1., 2., 3., 4.]],
                              [[1., 2., 3., 4.],
@@ -136,7 +136,7 @@ def setup_method(self):
         """Set up the tests."""
         self.reader = GACKLMReader()
 
-    @mock.patch("pygac.klm_reader.get_tsm_idx")
+    @mock.patch('pygac.klm_reader.get_tsm_idx')
     def test_get_tsm_pixels(self, get_tsm_idx):
         """Test channel set used for TSM correction."""
         ones = np.ones((409, 100))
@@ -174,7 +174,7 @@ def setup_method(self):
     def test_get_ch3_switch(self):
         """Test channel 3 identification."""
         self.reader.scans = {
-            "scan_line_bit_field": np.array([1, 2, 3, 4, 5, 6])}
+            'scan_line_bit_field': np.array([1, 2, 3, 4, 5, 6])}
         switch_exp = np.array([1, 2, 3, 0, 1, 2])
         numpy.testing.assert_array_equal(
             self.reader.get_ch3_switch(), switch_exp)
diff --git a/pygac/tests/test_noaa_calibration_coefficients.py b/pygac/tests/test_noaa_calibration_coefficients.py
index 8a0c0a9b..af1ef030 100644
--- a/pygac/tests/test_noaa_calibration_coefficients.py
+++ b/pygac/tests/test_noaa_calibration_coefficients.py
@@ -119,11 +119,11 @@ class TestCalibrationCoefficientsHandling(unittest.TestCase):
     @mock.patch("pygac.calibration.noaa.open", mock.mock_open(read_data=user_json_file))
     def test_user_coefficients_file(self):
         if sys.version_info.major < 3:
-            cal = Calibrator("noaa19", coeffs_file="/path/to/unknow/defaults.json")
+            cal = Calibrator('noaa19', coeffs_file="/path/to/unknow/defaults.json")
         else:
             with self.assertWarnsRegex(RuntimeWarning,
                                        "Unknown calibration coefficients version!"):
-                cal = Calibrator("noaa19", coeffs_file="/path/to/unknow/defaults.json")
+                cal = Calibrator('noaa19', coeffs_file="/path/to/unknow/defaults.json")
 
         self.assertEqual(cal.dark_count[0], 0)
         self.assertEqual(cal.gain_switch[0], 1000)
@@ -183,13 +183,13 @@ def test_read_coeffs_warnings(self):
         """Test warnings issued by Calibrator.read_coeffs."""
         version_dicts = [
             # Non-nominal coefficients
-            {"name": "v123",
-             "status": CoeffStatus.PROVISIONAL},
+            {'name': 'v123',
+             'status': CoeffStatus.PROVISIONAL},
             # Unknown coefficients
-            {"name": None,
-             "status": None}
+            {'name': None,
+             'status': None}
         ]
-        with mock.patch.object(Calibrator, "version_hashs") as version_hashs:
+        with mock.patch.object(Calibrator, 'version_hashs') as version_hashs:
             for version_dict in version_dicts:
                 version_hashs.get.return_value = version_dict
                 with self.assertWarns(RuntimeWarning):
diff --git a/pygac/tests/test_pod.py b/pygac/tests/test_pod.py
index f9d89a46..ace0f7ae 100644
--- a/pygac/tests/test_pod.py
+++ b/pygac/tests/test_pod.py
@@ -51,31 +51,31 @@ def setUp(self):
 
     def test__validate_header(self):
         """Test the header validation"""
-        filename = b"NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        head = {"data_set_name": filename}
+        filename = b'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        head = {'data_set_name': filename}
         GACPODReader._validate_header(head)
         # wrong name pattern
         with self.assertRaisesRegex(ReaderError,
-                                    "Data set name .* does not match!"):
-            head = {"data_set_name": b"abc.txt"}
+                                    'Data set name .* does not match!'):
+            head = {'data_set_name': b'abc.txt'}
             GACPODReader._validate_header(head)
         # wrong platform
-        name = b"NSS.GHRR.NL.D02187.S1904.E2058.B0921517.GC"
+        name = b'NSS.GHRR.NL.D02187.S1904.E2058.B0921517.GC'
         with self.assertRaisesRegex(ReaderError,
                                     'Improper platform id "NL"!'):
-            head = {"data_set_name": name}
+            head = {'data_set_name': name}
             GACPODReader._validate_header(head)
         # wrong transfer mode
-        name = filename.replace(b"GHRR", b"LHRR")
+        name = filename.replace(b'GHRR', b'LHRR')
         with self.assertRaisesRegex(ReaderError,
                                     'Improper transfer mode "LHRR"!'):
-            head = {"data_set_name": name}
+            head = {'data_set_name': name}
             GACPODReader._validate_header(head)
         # other change reader
-        head = {"data_set_name": name}
+        head = {'data_set_name': name}
         LACPODReader._validate_header(head)
 
-    @mock.patch("pygac.reader.Reader.get_calibrated_channels")
+    @mock.patch('pygac.reader.Reader.get_calibrated_channels')
     def test__get_calibrated_channels_uniform_shape(self, get_channels):
         """Test the uniform shape as required by gac_io.save_gac."""
         channels = np.arange(2*2*5, dtype=float).reshape((2, 2, 5))
@@ -97,24 +97,24 @@ def test_decode_timestamps(self):
 
         # Test whether PODReader decodes them correctly
         self.assertEqual(GACPODReader.decode_timestamps(t2000_enc), t2000_ref,
-                         msg="Timestamp after 2000 was decoded incorrectly")
+                         msg='Timestamp after 2000 was decoded incorrectly')
         self.assertEqual(GACPODReader.decode_timestamps(t1900_enc), t1900_ref,
-                         msg="Timestamp before 2000 was decoded incorrectly")
+                         msg='Timestamp before 2000 was decoded incorrectly')
 
-    @mock.patch("pygac.gac_pod.GACPODReader.decode_timestamps")
+    @mock.patch('pygac.gac_pod.GACPODReader.decode_timestamps')
     def test_get_header_timestamp(self, decode_timestamps):
         """Test readout of header timestamp."""
-        self.reader.head = {"start_time": 123}
+        self.reader.head = {'start_time': 123}
         decode_timestamps.return_value = np.array(
             [2019]), np.array([123]), np.array([123456])
         time = self.reader.get_header_timestamp()
         decode_timestamps.assert_called_with(123)
         self.assertEqual(time, dt.datetime(2019, 5, 3, 0, 2, 3, 456000))
 
-    @mock.patch("pygac.gac_pod.GACPODReader.decode_timestamps")
+    @mock.patch('pygac.gac_pod.GACPODReader.decode_timestamps')
     def test_get_times(self, decode_timestamps):
         """Test getting times."""
-        self.reader.scans = {"time_code": 123}
+        self.reader.scans = {'time_code': 123}
         self.reader._get_times()
         decode_timestamps.assert_called_with(123)
 
@@ -132,7 +132,7 @@ def test_get_lonlat(self):
         numpy.testing.assert_array_equal(lons, lons_exp)
         numpy.testing.assert_array_equal(lats, lats_exp)
 
-    @mock.patch("pygac.pod_reader.get_tsm_idx")
+    @mock.patch('pygac.pod_reader.get_tsm_idx')
     def test_get_tsm_pixels(self, get_tsm_idx):
         """Test channel set used for TSM correction."""
         ones = np.ones((409, 100))
@@ -157,7 +157,7 @@ def test_quality_indicators(self):
             QFlag.FATAL_FLAG,  # 100...00
             QFlag.CALIBRATION | QFlag.NO_EARTH_LOCATION,
             QFlag.TIME_ERROR | QFlag.DATA_GAP,
-        ], dtype=">u4")
+        ], dtype='>u4')
         # check if the bits look as expected
         bits = np.unpackbits(quality_indicators.view(np.uint8)).reshape((-1, 32))
         # For a big endian integer, the number 1 fills only the last of the 32 bits
@@ -188,10 +188,10 @@ def test_quality_indicators(self):
             expected_mask
         )
 
-    @mock.patch("pygac.pod_reader.get_lonlatalt")
-    @mock.patch("pygac.pod_reader.compute_pixels")
-    @mock.patch("pygac.reader.Reader.get_tle_lines")
-    @mock.patch("pygac.pod_reader.avhrr_gac")
+    @mock.patch('pygac.pod_reader.get_lonlatalt')
+    @mock.patch('pygac.pod_reader.compute_pixels')
+    @mock.patch('pygac.reader.Reader.get_tle_lines')
+    @mock.patch('pygac.pod_reader.avhrr_gac')
     def test__adjust_clock_drift(self, avhrr_gac, get_tle_lines,
                                  compute_pixels, get_lonlatalt):
         """Test the clock drift adjustment."""
@@ -209,7 +209,7 @@ def test__adjust_clock_drift(self, avhrr_gac, get_tle_lines,
         #  '1980-01-01T00:00:03.500', '1980-01-01T00:00:04.000',
         #  '1980-01-01T00:00:04.500', '1980-01-01T00:00:05.000']
         scan_utcs = (
-            (1000 * scan_rate * (scan_lines - scan_lines[0])).astype("timedelta64[ms]")
+            (1000 * scan_rate * (scan_lines - scan_lines[0])).astype('timedelta64[ms]')
             + np.datetime64("1980", "ms")
         )
         # For the geolocations, we assume an artificial swath of two pixels width
@@ -229,7 +229,7 @@ def test__adjust_clock_drift(self, avhrr_gac, get_tle_lines,
         #  '1980-01-01T00:00:00.750', '1980-01-01T00:00:01.250']
         offset = 3.75
         scan_offsets = offset*np.ones_like(scan_lines, dtype=float)  # seconds
-        expected_utcs = scan_utcs - (1000*scan_offsets).astype("timedelta64[ms]")
+        expected_utcs = scan_utcs - (1000*scan_offsets).astype('timedelta64[ms]')
 
         # the adjustment of geolocations should keep the lons unchanged,
         # but should shift the lats by scan_angel * offset / scan_rate
@@ -283,13 +283,13 @@ def test__adjust_clock_drift(self, avhrr_gac, get_tle_lines,
         # undo changes to clock_offsets_txt
         clock_offsets_txt.pop(sat_name)
 
-    @mock.patch("pygac.pod_reader.get_offsets")
-    @mock.patch("pygac.reader.Reader.get_tle_lines")
+    @mock.patch('pygac.pod_reader.get_offsets')
+    @mock.patch('pygac.reader.Reader.get_tle_lines')
     def test__adjust_clock_drift_without_tle(self, get_tle_lines, get_offsets):
         """Test that clockdrift adjustment can handle missing TLE data."""
         reader = self.reader
-        reader.utcs = np.zeros(10, dtype="datetime64[ms]")
+        reader.utcs = np.zeros(10, dtype='datetime64[ms]')
         reader.scans = {"scan_line_number": np.arange(10)}
         get_offsets.return_value = np.zeros(10), np.zeros(10)
-        get_tle_lines.side_effect = NoTLEData("No TLE data available")
+        get_tle_lines.side_effect = NoTLEData('No TLE data available')
         reader._adjust_clock_drift()  # should pass without errors
diff --git a/pygac/tests/test_reader.py b/pygac/tests/test_reader.py
index 3acb0881..cfa6b03d 100644
--- a/pygac/tests/test_reader.py
+++ b/pygac/tests/test_reader.py
@@ -70,9 +70,9 @@ def __init__(self, *args, **kwargs):
         scans["scan_line_number"] = np.arange(self.along_track)
         scans["sensor_data"] = 128
         self.scans = scans
-        self.head = {"foo": "bar"}
-        self.head = np.rec.fromrecords([("bar", ),],names="foo")
-        self.spacecraft_name = "noaa6"
+        self.head = {'foo': 'bar'}
+        self.head = np.rec.fromrecords([("bar", ),],names='foo')
+        self.spacecraft_name = 'noaa6'
 
     def _get_times(self):
         year = np.full(self.along_track, 1970, dtype=int)
@@ -124,9 +124,9 @@ class TestGacReader(unittest.TestCase):
 
     longMessage = True
 
-    @mock.patch.multiple("pygac.gac_reader.GACReader",
+    @mock.patch.multiple('pygac.gac_reader.GACReader',
                          __abstractmethods__=set())
-    @mock.patch("pygac.gac_reader.gtp.gac_lat_lon_interpolator")
+    @mock.patch('pygac.gac_reader.gtp.gac_lat_lon_interpolator')
     def setUp(self, interpolator, *mocks):
         """Set up the tests."""
         self.interpolator = interpolator
@@ -135,8 +135,8 @@ def setUp(self, interpolator, *mocks):
     def test_filename(self):
         """Test the setter of the filename property."""
         # test path with .gz extension
-        filename = "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        filepath = "/path/to/" + filename + ".gz"
+        filename = 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        filepath = '/path/to/' + filename + '.gz'
         self.reader.filename = filepath
         self.assertEqual(self.reader.filename, filename)
         self.reader.filename = None
@@ -148,94 +148,94 @@ def test_filename(self):
     def test__read_scanlines(self):
         """Test the scanline extraction."""
         self.reader.scanline_type = np.dtype([
-            ("a", "S2"), ("b", "<i4")])
+            ('a', 'S2'), ('b', '<i4')])
         # request more scan lines than available
         with self.assertWarnsRegex(RuntimeWarning,
                                    "Unexpected number of scanlines!"):
-            buffer = (b"a\x00\x01\x00\x00\x00"
-                      b"b\x00\x02\x00\x00\x00"
-                      b"c\x00\x03\x00\x00\x00")
+            buffer = (b'a\x00\x01\x00\x00\x00'
+                      b'b\x00\x02\x00\x00\x00'
+                      b'c\x00\x03\x00\x00\x00')
             count = 4
             self.reader._read_scanlines(buffer, count)
         # check the output
         first_line = self.reader.scans[0]
-        self.assertEqual(first_line["a"], b"a")
-        self.assertEqual(first_line["b"], 1)
+        self.assertEqual(first_line['a'], b'a')
+        self.assertEqual(first_line['b'], 1)
 
     def test__validate_header(self):
         """Test the header validation."""
         # wrong name pattern
         with self.assertRaisesRegex(ReaderError,
-                                    "Data set name .* does not match!"):
-            head = {"data_set_name": b"abc.txt"}
+                                    'Data set name .* does not match!'):
+            head = {'data_set_name': b'abc.txt'}
             self.reader._validate_header(head)
         # Unicode errors are now caught with the same exception.
         with self.assertRaisesRegex(ReaderError,
-                                    "Data set name .* does not match!"):
-            head = {"data_set_name": b"\xea\xf8"}
+                                    'Data set name .* does not match!'):
+            head = {'data_set_name': b'\xea\xf8'}
             self.reader._validate_header(head)
 
     def test__correct_data_set_name_ebcdic_encoded_header_invalid_path(self):
         """Test the data_set_name correction in file header."""
-        inv_filename = "InvalidFileName"
-        inv_filepath = "path/to/" + inv_filename
+        inv_filename = 'InvalidFileName'
+        inv_filepath = 'path/to/' + inv_filename
 
-        expected_data_set_name = "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        val_head = {"data_set_name": "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI".encode("cp500")}
+        expected_data_set_name = 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        val_head = {'data_set_name': 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'.encode("cp500")}
         head = self.reader._correct_data_set_name(val_head.copy(), inv_filepath)
-        assert head["data_set_name"] == expected_data_set_name.encode()
+        assert head['data_set_name'] == expected_data_set_name.encode()
 
     def test__correct_data_set_name_valid_header_and_file(self):
         """Test the data_set_name correction in file header."""
-        val_filename = "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        val_filepath = "path/to/" + val_filename
-        val_head = {"data_set_name": b"NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"}
+        val_filename = 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        val_filepath = 'path/to/' + val_filename
+        val_head = {'data_set_name': b'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'}
         # Note: always pass a copy to _correct_data_set_name, because
         #       the input header is modified in place.
         # enter a valid data_set_name and filepath
         head = self.reader._correct_data_set_name(val_head.copy(), val_filepath)
-        assert head["data_set_name"] == val_filename.encode()
+        assert head['data_set_name'] == val_filename.encode()
 
     def test__correct_data_set_name_invalid_header_and_valid_file(self):
         """Test the data_set_name correction in file header."""
-        val_filename = "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        val_filepath = "path/to/" + val_filename
-        inv_head = {"data_set_name": b"InvalidDataSetName"}
+        val_filename = 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        val_filepath = 'path/to/' + val_filename
+        inv_head = {'data_set_name': b'InvalidDataSetName'}
 
         # enter an invalid data_set_name, but valid filepath
         head = self.reader._correct_data_set_name(inv_head.copy(), val_filepath)
-        assert head["data_set_name"] == val_filename.encode()
+        assert head['data_set_name'] == val_filename.encode()
 
     def test__correct_data_set_name_invalid_header_and_file(self):
         """Test the data_set_name correction in file header."""
-        inv_filename = "InvalidFileName"
-        inv_filepath = "path/to/" + inv_filename
-        inv_head = {"data_set_name": b"InvalidDataSetName"}
-        with self.assertRaisesRegex(ReaderError, "Cannot determine data_set_name!"):
+        inv_filename = 'InvalidFileName'
+        inv_filepath = 'path/to/' + inv_filename
+        inv_head = {'data_set_name': b'InvalidDataSetName'}
+        with self.assertRaisesRegex(ReaderError, 'Cannot determine data_set_name!'):
             _ = self.reader._correct_data_set_name(inv_head.copy(), inv_filepath)
 
     def test__correct_data_set_name_valid_header_invalid_file(self):
         """Test the data_set_name correction in file header."""
-        val_head = {"data_set_name": b"NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"}
-        inv_filename = "InvalidFileName"
-        inv_filepath = "path/to/" + inv_filename
+        val_head = {'data_set_name': b'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'}
+        inv_filename = 'InvalidFileName'
+        inv_filepath = 'path/to/' + inv_filename
 
         # enter a valid data_set_name, and an invalid filepath
         # should be fine, because the data_set_name is the pefered source
         head = self.reader._correct_data_set_name(val_head.copy(), inv_filepath)
-        assert head["data_set_name"] == val_head["data_set_name"]
+        assert head['data_set_name'] == val_head['data_set_name']
 
     def test__correct_data_set_name_valid_header_pathlib_file(self):
         """Test the data_set_name correction in file header."""
-        val_filename = "NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"
-        val_filepath = "path/to/" + val_filename
-        val_head = {"data_set_name": b"NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI"}
+        val_filename = 'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'
+        val_filepath = 'path/to/' + val_filename
+        val_head = {'data_set_name': b'NSS.GHRR.TN.D80001.S0332.E0526.B0627173.WI'}
 
         fs_filepath = FakePath(val_filepath)
         head = self.reader._correct_data_set_name(val_head.copy(), fs_filepath)
-        self.assertEqual(head["data_set_name"], val_filename.encode())
+        self.assertEqual(head['data_set_name'], val_filename.encode())
 
-    @mock.patch("pygac.reader.Reader.get_calibrated_channels")
+    @mock.patch('pygac.reader.Reader.get_calibrated_channels')
     def test__get_calibrated_channels_uniform_shape(self, get_channels):
         """Test the uniform shape as required by gac_io.save_gac."""
         # check if it raises the assertion error
@@ -257,9 +257,9 @@ def test_to_datetime64(self):
         """Test conversion from (year, jday, msec) to datetime64."""
         t0 = GACReader.to_datetime64(year=np.array(1970), jday=np.array(1),
                                      msec=np.array(0))
-        self.assertEqual(t0.astype("i8"), 0,
-                         msg="Conversion (year, jday, msec) to datetime64 "
-                             "is not correct")
+        self.assertEqual(t0.astype('i8'), 0,
+                         msg='Conversion (year, jday, msec) to datetime64 '
+                             'is not correct')
 
     def test_to_datetime(self):
         """Test conversion from datetime64 to datetime."""
@@ -271,10 +271,10 @@ def test_lineno2msec(self):
         """Test scanline timestamp estimation."""
         self.assertEqual(self.reader.lineno2msec(12345), 6172000)
 
-    @mock.patch("pygac.reader.Reader.update_meta_data")
-    @mock.patch("pygac.gac_reader.GACReader._get_lonlat")
-    @mock.patch("pygac.gac_reader.GACReader._get_corrupt_mask")
-    @mock.patch("pygac.gac_reader.GACReader._adjust_clock_drift")
+    @mock.patch('pygac.reader.Reader.update_meta_data')
+    @mock.patch('pygac.gac_reader.GACReader._get_lonlat')
+    @mock.patch('pygac.gac_reader.GACReader._get_corrupt_mask')
+    @mock.patch('pygac.gac_reader.GACReader._adjust_clock_drift')
     def test_get_lonlat(self, adjust_clockdrift,
                         get_corrupt_mask, get_lonlat,
                         update_meta_data):
@@ -330,10 +330,10 @@ def test_get_lonlat(self, adjust_clockdrift,
         for method in methods:
             method.asser_not_called()
 
-    @mock.patch("pygac.reader.Reader.update_meta_data")
-    @mock.patch("pygac.gac_reader.GACReader._get_corrupt_mask")
-    @mock.patch("pygac.gac_reader.GACReader._adjust_clock_drift")
-    @mock.patch("pygac.gac_reader.GACReader._get_lonlat")
+    @mock.patch('pygac.reader.Reader.update_meta_data')
+    @mock.patch('pygac.gac_reader.GACReader._get_corrupt_mask')
+    @mock.patch('pygac.gac_reader.GACReader._adjust_clock_drift')
+    @mock.patch('pygac.gac_reader.GACReader._get_lonlat')
     def test_interpolate(self, _get_lonlat, _adjust_clock_drift,
                          _get_corrupt_mask, update_meta_data):
         """Test interpolate method in get_lonlat."""
@@ -350,7 +350,7 @@ def test_interpolate(self, _get_lonlat, _adjust_clock_drift,
         self.assertEqual(lons.shape[1], 409)
         self.interpolator.assert_called_once_with(lr_lons, lr_lats)
 
-    @mock.patch("pygac.gac_reader.GACReader._get_corrupt_mask")
+    @mock.patch('pygac.gac_reader.GACReader._get_corrupt_mask')
     def test_get_corrupt_mask(self, get_corrupt_mask):
         """Test common computation of corrupt scanline mask."""
         get_corrupt_mask.return_value = [1, 2, 3]
@@ -365,51 +365,51 @@ def test_midnight_scanline(self):
         """Test midnight scanline computation."""
         # Define test cases...
         # ... midnight scanline exists
-        utcs1 = np.array([-3, -2, -1, 0, 1, 2, 3]).astype("datetime64[ms]")
+        utcs1 = np.array([-3, -2, -1, 0, 1, 2, 3]).astype('datetime64[ms]')
         scanline1 = 2
 
         # ... midnight scanline does not exist
-        utcs2 = np.array([1, 2, 3]).astype("datetime64[ms]")
+        utcs2 = np.array([1, 2, 3]).astype('datetime64[ms]')
         scanline2 = None
 
         for utcs, scan_line in zip((utcs1, utcs2), (scanline1, scanline2)):
             self.reader.utcs = utcs
             self.assertEqual(self.reader.get_midnight_scanline(), scan_line,
-                             msg="Incorrect midnight scanline")
+                             msg='Incorrect midnight scanline')
 
     def test_miss_lines(self):
         """Test detection of missing scanlines."""
         lines = [2, 4, 5, 6, 10, 11, 12]
         miss_lines_ref = [1, 3, 7, 8, 9]
         self.reader.scans = np.zeros(
-            len(lines), dtype=[("scan_line_number", "i2")])
-        self.reader.scans["scan_line_number"] = lines
+            len(lines), dtype=[('scan_line_number', 'i2')])
+        self.reader.scans['scan_line_number'] = lines
         miss_lines = self.reader.get_miss_lines()
         self.assertTrue((miss_lines == miss_lines_ref).all(),
-                        msg="Missing scanlines not detected correctly")
+                        msg='Missing scanlines not detected correctly')
         self.assertEqual(miss_lines.dtype, int)
 
     def test_tle2datetime64(self, *mocks):
         """Test conversion from TLE timestamps to datetime64."""
         dates = np.array([70365.1234, 18001.25])
-        dates64_exp = [np.datetime64(datetime.datetime(1970, 12, 31, 2, 57, 41, 760000), "[ms]"),
-                       np.datetime64(datetime.datetime(2018, 1, 1, 6, 0), "[ms]")]
+        dates64_exp = [np.datetime64(datetime.datetime(1970, 12, 31, 2, 57, 41, 760000), '[ms]'),
+                       np.datetime64(datetime.datetime(2018, 1, 1, 6, 0), '[ms]')]
         dates64 = GACReader.tle2datetime64(dates)
         self.assertTrue(np.all(dates64 == dates64_exp))
 
-    @mock.patch("pygac.gac_reader.GACReader.get_times")
-    @mock.patch("pygac.gac_reader.GACReader.get_tle_file")
-    @mock.patch("pygac.gac_reader.GACReader.read_tle_file")
+    @mock.patch('pygac.gac_reader.GACReader.get_times')
+    @mock.patch('pygac.gac_reader.GACReader.get_tle_file')
+    @mock.patch('pygac.gac_reader.GACReader.read_tle_file')
     def test_get_tle_lines(self, read_tle_file, *mocks):
         """Test identification of closest TLE lines."""
-        tle_data = ["1 38771U 12049A   18363.63219793 -.00000013  00000-0  14176-4 0  9991\r\n",
-                    "2 38771  98.7297  60.1350 0002062  95.9284  25.0713 14.21477560325906\r\n",
-                    "1 38771U 12049A   18364.62426010 -.00000015  00000-0  13136-4 0  9990\r\n",  # 2018-12-30 14:58
-                    "2 38771  98.7295  61.1159 0002062  94.5796  60.2561 14.21477636326047\r\n",
-                    "1 38771U 12049A   18364.94649306 -.00000018  00000-0  12040-4 0  9996\r\n",  # 2018-12-30 22:42
-                    "2 38771  98.7295  61.4345 0002060  94.1226 268.7521 14.21477633326092\r\n",
-                    "1 38771U 12049A   18365.81382142 -.00000015  00000-0  13273-4 0  9991\r\n",
-                    "2 38771  98.7294  62.2921 0002057  92.7653  26.0030 14.21477711326215\r\n"]
+        tle_data = ['1 38771U 12049A   18363.63219793 -.00000013  00000-0  14176-4 0  9991\r\n',
+                    '2 38771  98.7297  60.1350 0002062  95.9284  25.0713 14.21477560325906\r\n',
+                    '1 38771U 12049A   18364.62426010 -.00000015  00000-0  13136-4 0  9990\r\n',  # 2018-12-30 14:58
+                    '2 38771  98.7295  61.1159 0002062  94.5796  60.2561 14.21477636326047\r\n',
+                    '1 38771U 12049A   18364.94649306 -.00000018  00000-0  12040-4 0  9996\r\n',  # 2018-12-30 22:42
+                    '2 38771  98.7295  61.4345 0002060  94.1226 268.7521 14.21477633326092\r\n',
+                    '1 38771U 12049A   18365.81382142 -.00000015  00000-0  13273-4 0  9991\r\n',
+                    '2 38771  98.7294  62.2921 0002057  92.7653  26.0030 14.21477711326215\r\n']
 
         expected = {
             datetime.datetime(2018, 12, 20, 12, 0): None,
@@ -422,7 +422,7 @@ def test_get_tle_lines(self, read_tle_file, *mocks):
 
         read_tle_file.return_value = tle_data
         for time, tle_idx in expected.items():
-            self.reader.utcs = np.array([time], dtype="datetime64[ms]")
+            self.reader.utcs = np.array([time], dtype='datetime64[ms]')
             self.reader.tle_lines = None
             if tle_idx is None:
                 self.assertRaises(NoTLEData, self.reader.get_tle_lines)
@@ -431,10 +431,10 @@ def test_get_tle_lines(self, read_tle_file, *mocks):
                 self.assertEqual(tle1, tle_data[tle_idx])
                 self.assertEqual(tle2, tle_data[tle_idx + 1])
 
-    @mock.patch("pygac.reader.Reader.get_tle_lines")
+    @mock.patch('pygac.reader.Reader.get_tle_lines')
     def test_get_sat_angles_without_tle_at_nadir(self, get_tle_lines):
         """Test that the get satellite angles without tle at nadir."""
-        get_tle_lines.side_effect = NoTLEData("No TLE data available")
+        get_tle_lines.side_effect = NoTLEData('No TLE data available')
         rng = np.random.RandomState(125)
         self.reader.lons = rng.rand(100, 409) * 90
         self.reader.lats = rng.rand(100, 409) * 90
@@ -444,10 +444,10 @@ def test_get_sat_angles_without_tle_at_nadir(self, get_tle_lines):
         self.assertEqual(np.sum(np.isnan(sat_elev)), 0)
         np.testing.assert_allclose(sat_elev[:, 204], 90., atol=0.01)
 
-    @mock.patch("pygac.reader.Reader.get_tle_lines")
+    @mock.patch('pygac.reader.Reader.get_tle_lines')
     def test_get_sat_angles_without_tle(self, get_tle_lines):
         """Test the get satellite angles without tle."""
-        get_tle_lines.side_effect = NoTLEData("No TLE data available")
+        get_tle_lines.side_effect = NoTLEData('No TLE data available')
 
         # Test data correspond to columns 0:2, 201:208 and 407:409. Extracted like this:
         # self.lons[0:5, [0, 1, 201, 202, 203, 204, 205, 206, 207, -2, -1]]
@@ -498,7 +498,7 @@ def test_get_sat_angles_without_tle(self, get_tle_lines):
         np.testing.assert_allclose(sat_elev[:, 0], expected_sat_elev_0, atol=1.0)
         np.testing.assert_allclose(sat_elev[:, 5], expected_sat_elev_204, atol=1.0)
 
-    @mock.patch("pygac.gac_reader.GACReader._get_corrupt_mask")
+    @mock.patch('pygac.gac_reader.GACReader._get_corrupt_mask')
     def test_get_angles(self, get_corrupt_mask):
         """Test get_angles function of the reader."""
         # Line: 1, 649, 6198 and 12658 from Tiros-N file (1980-01-03 11:47)
@@ -515,8 +515,8 @@ def test_get_angles(self, get_corrupt_mask):
         self.reader.utcs = np.array(
             [315748035469, 315748359969,
              315751135469, 315754371969,
-             315754371969]).astype("datetime64[ms]")
-        self.reader.spacecrafts_orbital = {25: "tiros n"}
+             315754371969]).astype('datetime64[ms]')
+        self.reader.spacecrafts_orbital = {25: 'tiros n'}
         self.reader.spacecraft_id = 25
         expected_sat_azi = np.array(
             [-76.90, 11.08, 145.33, -50.01, np.nan])[:, np.newaxis]
@@ -539,13 +539,13 @@ def test_get_angles(self, get_corrupt_mask):
 
     def test_get_tle_file(self):
         """Test get_tle_file."""
-        self.reader.tle_dir = "/tle/dir"
-        self.reader.tle_name = "tle_%(satname)s.txt"
-        self.reader.spacecraft_name = "ISS"
+        self.reader.tle_dir = '/tle/dir'
+        self.reader.tle_name = 'tle_%(satname)s.txt'
+        self.reader.spacecraft_name = 'ISS'
         tle_file = self.reader.get_tle_file()
-        self.assertEqual(tle_file, "/tle/dir/tle_ISS.txt")
+        self.assertEqual(tle_file, '/tle/dir/tle_ISS.txt')
 
-    @mock.patch("pygac.gac_reader.GACReader.get_tsm_pixels")
+    @mock.patch('pygac.gac_reader.GACReader.get_tsm_pixels')
     def test_mask_tsm_pixels(self, get_tsm_pixels):
         """Test masking of pixels affected by the scan motor issue."""
         get_tsm_pixels.return_value = ([0, 1], [0, 1])
@@ -570,10 +570,10 @@ def test_correct_scan_line_numbers(self):
         scans, expected = _get_scanline_numbers(14000)
         self.reader.scans = scans
         self.reader.correct_scan_line_numbers()
-        numpy.testing.assert_array_equal(self.reader.scans["scan_line_number"],
+        numpy.testing.assert_array_equal(self.reader.scans['scan_line_number'],
                                          expected)
 
-    @mock.patch("pygac.gac_reader.GACReader.get_header_timestamp")
+    @mock.patch('pygac.gac_reader.GACReader.get_header_timestamp')
     def test_correct_times_thresh(self, get_header_timestamp):
         """Test correction of scanline timestamps."""
         header_time = datetime.datetime(2016, 8, 16, 16, 7, 36)
@@ -604,29 +604,29 @@ def test_calculate_sun_earth_distance_correction(self):
         """Test the calculate sun earth distance correction method."""
         self.reader.utcs = np.array([315748035469, 315748359969,
                                      315751135469, 315754371969,
-                                     315754371969]).astype("datetime64[ms]")
+                                     315754371969]).astype('datetime64[ms]')
         corr = self.reader.get_sun_earth_distance_correction()
         numpy.testing.assert_almost_equal(corr, 0.96660494, decimal=7)
 
-    @mock.patch("pygac.reader.Reader.get_sun_earth_distance_correction")
-    @mock.patch("pygac.reader.Reader.get_midnight_scanline")
-    @mock.patch("pygac.reader.Reader.get_miss_lines")
+    @mock.patch('pygac.reader.Reader.get_sun_earth_distance_correction')
+    @mock.patch('pygac.reader.Reader.get_midnight_scanline')
+    @mock.patch('pygac.reader.Reader.get_miss_lines')
     def test_update_metadata(self,
                              get_miss_lines,
                              get_midnight_scanline,
                              get_sun_earth_distance_correction):
         """Test updating the metadata."""
-        get_miss_lines.return_value = "miss_lines"
-        get_midnight_scanline.return_value = "midn_line"
-        get_sun_earth_distance_correction.return_value = "factor"
-        self.reader.head = {"foo": "bar"}
+        get_miss_lines.return_value = 'miss_lines'
+        get_midnight_scanline.return_value = 'midn_line'
+        get_sun_earth_distance_correction.return_value = 'factor'
+        self.reader.head = {'foo': 'bar'}
 
         self.reader.update_meta_data()
 
-        mda_exp = {"midnight_scanline": "midn_line",
-                   "missing_scanlines": "miss_lines",
-                   "sun_earth_distance_correction_factor": "factor",
-                   "gac_header": {"foo": "bar"}}
+        mda_exp = {'midnight_scanline': 'midn_line',
+                   'missing_scanlines': 'miss_lines',
+                   'sun_earth_distance_correction_factor': 'factor',
+                   'gac_header': {'foo': 'bar'}}
         self.assertDictEqual(self.reader.meta_data, mda_exp)
 
 
@@ -657,7 +657,7 @@ class TestLacReader(unittest.TestCase):
 
     longMessage = True
 
-    @mock.patch.multiple("pygac.lac_reader.LACReader",
+    @mock.patch.multiple('pygac.lac_reader.LACReader',
                          __abstractmethods__=set())
     def setUp(self, *mocks):
         """Set up the tests."""
@@ -665,7 +665,7 @@ def setUp(self, *mocks):
 
     def test_lac_reader_accepts_FRAC(self):
         """Test the header validation."""
-        head = {"data_set_name": b"NSS.FRAC.M1.D19115.S2352.E0050.B3425758.SV"}
+        head = {'data_set_name': b'NSS.FRAC.M1.D19115.S2352.E0050.B3425758.SV'}
         self.reader._validate_header(head)
 
     def test_correct_scan_line_numbers(self):
@@ -673,7 +673,7 @@ def test_correct_scan_line_numbers(self):
         scans, expected = _get_scanline_numbers(22000)
         self.reader.scans = scans
         self.reader.correct_scan_line_numbers()
-        numpy.testing.assert_array_equal(self.reader.scans["scan_line_number"],
+        numpy.testing.assert_array_equal(self.reader.scans['scan_line_number'],
                                          expected)
 
 
@@ -689,12 +689,12 @@ def pod_file_with_tbm_header(tmp_path):
     tbm_header["ending_latitude"] = b"+22"
     tbm_header["beginning_longitude"] = b"-004"
     tbm_header["ending_longitude"] = b"+032"
-    tbm_header["start_hour"] = b"AL"
-    tbm_header["start_minute"] = b"L "
-    tbm_header["number_of_minutes"] = b"ALL"
-    tbm_header["appended_data_flag"] = b"Y"
-    tbm_header["channel_select_flag"][0, :5] = b"\x01"
-    tbm_header["sensor_data_word_size"] = b"10"
+    tbm_header["start_hour"] = b'AL'
+    tbm_header["start_minute"] = b'L '
+    tbm_header["number_of_minutes"] = b'ALL'
+    tbm_header["appended_data_flag"] = b'Y'
+    tbm_header["channel_select_flag"][0, :5] = b'\x01'
+    tbm_header["sensor_data_word_size"] = b'10'
 
     header = np.zeros(1, dtype=header3)
     header["noaa_spacecraft_identification_code"] = 3
@@ -702,7 +702,7 @@ def pod_file_with_tbm_header(tmp_path):
     header["start_time"] = [51522, 181, 62790]
     header["number_of_scans"] = number_of_scans
     header["end_time"] = [51522, 195, 42286]
-    header["processing_block_id"] = b"3031919"
+    header["processing_block_id"] = b'3031919'
     header["ramp_auto_calibration"] = 0
     header["number_of_data_gaps"] = 0
     header["dacs_quality"] = [21, 7, 0, 0, 0, 0]
@@ -810,7 +810,7 @@ def test_read_to_dataset_is_a_dataset_including_channels_and_telemetry(pod_file_
     dataset = reader.read_as_dataset(pod_file_with_tbm_header)
     assert isinstance(dataset, xr.Dataset)
     assert dataset["channels"].shape == (3, 2048, 5)
-    assert dataset.attrs["processing_block_id"] == b"3031919"
+    assert dataset.attrs["processing_block_id"] == b'3031919'
     assert "times" in dataset.coords
     assert "scan_line_index" in dataset.coords
     assert "channel_name" in dataset.coords
diff --git a/pygac/tests/test_utils.py b/pygac/tests/test_utils.py
index 65f3a9ba..3361ca12 100644
--- a/pygac/tests/test_utils.py
+++ b/pygac/tests/test_utils.py
@@ -39,20 +39,20 @@ class TestUtils(unittest.TestCase):
 
     longMessage = True
 
-    @mock.patch("pygac.utils.open", mock.MagicMock(return_value=io.BytesIO(b"file content")))
+    @mock.patch('pygac.utils.open', mock.MagicMock(return_value=io.BytesIO(b'file content')))
     def test_file_opener_1(self):
         """Test if a file is redirected correctly through file_opener."""
-        with file_opener("path/to/file") as f:
+        with file_opener('path/to/file') as f:
             content = f.read()
-        self.assertEqual(content, b"file content")
+        self.assertEqual(content, b'file content')
 
     def test_file_opener_2(self):
         """Test file_opener with file objects and compression"""
         # prepare test
-        normal_message = b"normal message"
-        gzip_message_decoded = b"gzip message"
+        normal_message = b'normal message'
+        gzip_message_decoded = b'gzip message'
         with io.BytesIO() as f:
-            with gzip.open(f, mode="wb") as g:
+            with gzip.open(f, mode='wb') as g:
                 g.write(gzip_message_decoded)
             f.seek(0)
             gzip_message_encoded = f.read()
@@ -68,7 +68,7 @@ def test_file_opener_2(self):
                 message = g.read()
         self.assertEqual(message, gzip_message_decoded)
 
-    @mock.patch("pygac.utils.open", mock.MagicMock(side_effect=FileNotFoundError))
+    @mock.patch('pygac.utils.open', mock.MagicMock(side_effect=FileNotFoundError))
     def test_file_opener_3(self):
         """Test file_opener with PathLike object"""
         # prepare test
@@ -83,8 +83,8 @@ def __fspath__(self):
             def open(self):
                 return io.BytesIO(self.raw_bytes)
 
-        filename = "/path/to/file"
-        file_bytes = b"TestTestTest"
+        filename = '/path/to/file'
+        file_bytes = b'TestTestTest'
         test_pathlike = RawBytes(filename, file_bytes)
         with file_opener(test_pathlike) as f:
             content = f.read()
diff --git a/pygac/utils.py b/pygac/utils.py
index 1473d0bc..76a7fd9e 100644
--- a/pygac/utils.py
+++ b/pygac/utils.py
@@ -33,7 +33,7 @@
 def gzip_inspected(open_file):
     """Try to gzip decompress the file object if applicable."""
     try:
-        file_object = gzip.GzipFile(mode="rb", fileobj=open_file)
+        file_object = gzip.GzipFile(mode='rb', fileobj=open_file)
         file_object.read(1)
     except OSError:
         file_object = open_file
@@ -47,13 +47,13 @@ def file_opener(file):
     if isinstance(file, io.IOBase) and file.seekable():
         # avoid closing the file using nullcontext
         open_file = nullcontext(file)
-    elif hasattr(file, "open"):
+    elif hasattr(file, 'open'):
         try:
-            open_file = file.open(mode="rb")
+            open_file = file.open(mode='rb')
         except TypeError:
             open_file = file.open()
     else:
-        open_file = open(file, mode="rb")
+        open_file = open(file, mode='rb')
     # set open_file into context in case of lazy loading in __enter__ method.
     with open_file as file_object:
         yield gzip_inspected(file_object)
@@ -108,7 +108,7 @@ def check_user_scanlines(start_line, end_line, first_valid_lat=None,
         num_valid_lines = last_valid_lat - first_valid_lat + 1
     else:
         if along_track is None:
-            raise ValueError("Need along_track")
+            raise ValueError('Need along_track')
         num_valid_lines = along_track
 
     start_line = int(start_line)
@@ -119,10 +119,10 @@ def check_user_scanlines(start_line, end_line, first_valid_lat=None,
         end_line = num_valid_lines - 1
     elif end_line >= num_valid_lines:
         end_line = num_valid_lines - 1
-        LOG.warning("Given end line exceeds scanline range, resetting "
-                    "to {}".format(end_line))
+        LOG.warning('Given end line exceeds scanline range, resetting '
+                    'to {}'.format(end_line))
     if start_line > num_valid_lines:
-        raise ValueError("Given start line {} exceeds scanline range {}"
+        raise ValueError('Given start line {} exceeds scanline range {}'
                          .format(start_line, num_valid_lines))
     return start_line, end_line
 
@@ -239,13 +239,13 @@ def plot_correct_times_thresh(res, filename=None):
     """Visualize results of GACReader.correct_times_thresh."""
     import matplotlib.pyplot as plt
 
-    t = res["t"]
-    tcorr = res.get("tcorr")
-    n = res["n"]
-    offsets = res.get("offsets")
-    t0_head = res.get("t0_head")
-    max_diff_from_t0_head = res.get("max_diff_from_t0_head")
-    fail_reason = res.get("fail_reason", "Failed for unknown reason")
+    t = res['t']
+    tcorr = res.get('tcorr')
+    n = res['n']
+    offsets = res.get('offsets')
+    t0_head = res.get('t0_head')
+    max_diff_from_t0_head = res.get('max_diff_from_t0_head')
+    fail_reason = res.get('fail_reason', 'Failed for unknown reason')
 
     # Setup figure
     along_track = np.arange(t.size)
@@ -295,13 +295,13 @@ def plot_correct_scanline_numbers(res, filename=None):
     """Visualize results of GACReader.correct_scanline_numbers."""
     import matplotlib.pyplot as plt
 
-    along_track = res["along_track"]
-    n_orig = res["n_orig"]
-    n_corr = res["n_corr"]
-    within_range = res["within_range"]
-    thresh = res["thresh"]
-    diffs = res["diffs"]
-    nz_diffs = res["nz_diffs"]
+    along_track = res['along_track']
+    n_orig = res['n_orig']
+    n_corr = res['n_corr']
+    within_range = res['within_range']
+    thresh = res['thresh']
+    diffs = res['diffs']
+    nz_diffs = res['nz_diffs']
 
     # Setup figure
     _, (ax0, ax1) = plt.subplots(nrows=2)
@@ -327,6 +327,6 @@ def plot_correct_scanline_numbers(res, filename=None):
     plt.tight_layout()
 
     if filename:
-        plt.savefig(filename, bbox_inches="tight")
+        plt.savefig(filename, bbox_inches='tight')
     else:
         plt.show()
diff --git a/pyproject.toml b/pyproject.toml
index 28cbf745..8137cfe3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -67,4 +67,4 @@ version-file = "pygac/version.py"
 line-length = 120
 
 [tool.ruff.lint]
-select = ["E", "W", "F", "I", "Q"]
+select = ["E", "W", "F", "I"]