diff --git a/src/pyoperators/__init__.py b/src/pyoperators/__init__.py
index b8a464d..1eb2720 100644
--- a/src/pyoperators/__init__.py
+++ b/src/pyoperators/__init__.py
@@ -10,6 +10,7 @@
 - operators_pywt : (optional) loaded if PyWavelets is present.
 
 """
+
 from importlib.metadata import version as _version
 
 from .core import (
diff --git a/src/pyoperators/core.py b/src/pyoperators/core.py
index d08acdc..46b7f47 100644
--- a/src/pyoperators/core.py
+++ b/src/pyoperators/core.py
@@ -3,6 +3,7 @@
 which can be added, composed or multiplied by a scalar. See the
 Operator docstring for more information.
 """
+
 from __future__ import annotations
 
 import inspect
@@ -1233,16 +1234,20 @@ def _init_inout(
         flag_is = (
             'explicit'
             if self.shapein is not None
-            else 'implicit'
-            if self.reshapeout != Operator.reshapeout.__get__(self, type(self))
-            else 'unconstrained'
+            else (
+                'implicit'
+                if self.reshapeout != Operator.reshapeout.__get__(self, type(self))
+                else 'unconstrained'
+            )
         )
         flag_os = (
             'explicit'
             if self.shapeout is not None
-            else 'implicit'
-            if self.reshapein != Operator.reshapein.__get__(self, type(self))
-            else 'unconstrained'
+            else (
+                'implicit'
+                if self.reshapein != Operator.reshapein.__get__(self, type(self))
+                else 'unconstrained'
+            )
         )
         self._set_flags(shape_input=flag_is, shape_output=flag_os)
 
@@ -1779,9 +1784,11 @@ def __str__(self):
 
         # parentheses for AdditionOperator and BlockDiagonalOperator
         operands = [
-            f'({o})'
-            if isinstance(o, (AdditionOperator, BlockDiagonalOperator))
-            else str(o)
+            (
+                f'({o})'
+                if isinstance(o, (AdditionOperator, BlockDiagonalOperator))
+                else str(o)
+            )
             for o in self.operands
         ]
 
@@ -2440,9 +2447,11 @@ def _apply_rule_homothety(self, operands):
         """
         return sum(
             (
-                self._apply_rule_homothety_linear(list(group))
-                if islinear
-                else list(group)
+                (
+                    self._apply_rule_homothety_linear(list(group))
+                    if islinear
+                    else list(group)
+                )
                 for islinear, group in groupby(operands, lambda o: o.flags.linear)
             ),
             [],
@@ -3470,9 +3479,9 @@ def _validate_partition_composition(op1, op2):
             )
         )
 
-        return None if pout is None else merge_none(
-            op1.partitionout, pout
-        ), None if pin is None else merge_none(op2.partitionin, pin)
+        return None if pout is None else merge_none(op1.partitionout, pout), (
+            None if pin is None else merge_none(op2.partitionin, pin)
+        )
 
     @staticmethod
     def _rule_operator_commutative(self, op, cls):
diff --git a/src/pyoperators/flags.py b/src/pyoperators/flags.py
index 7db2a2c..c681e0f 100644
--- a/src/pyoperators/flags.py
+++ b/src/pyoperators/flags.py
@@ -4,6 +4,7 @@
 linear, square etc.
 
 """
+
 from collections import namedtuple
 
 
diff --git a/src/pyoperators/iterative/algorithms.py b/src/pyoperators/iterative/algorithms.py
index fec0895..33d8862 100644
--- a/src/pyoperators/iterative/algorithms.py
+++ b/src/pyoperators/iterative/algorithms.py
@@ -1,6 +1,7 @@
 """
 Implements iterative algorithm class.
 """
+
 from copy import copy
 
 import numpy as np
diff --git a/src/pyoperators/iterative/dli.py b/src/pyoperators/iterative/dli.py
index 6926a64..1c17e4b 100644
--- a/src/pyoperators/iterative/dli.py
+++ b/src/pyoperators/iterative/dli.py
@@ -10,6 +10,7 @@
 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.165.8284&rep=rep1&type=pdf
 
 """
+
 from copy import copy
 
 import numpy as np
diff --git a/src/pyoperators/iterative/linesearch.py b/src/pyoperators/iterative/linesearch.py
index c6c6f56..c2f35e3 100644
--- a/src/pyoperators/iterative/linesearch.py
+++ b/src/pyoperators/iterative/linesearch.py
@@ -15,6 +15,7 @@
 
 - LineSearch, LineSearchArmijo, LineSearchWolfe1; LineSearchWolfe2
 """
+
 import numpy as np
 
 from .criterions import Norm2
diff --git a/src/pyoperators/iterative/optimize.py b/src/pyoperators/iterative/optimize.py
index f37d9ea..ed564a3 100644
--- a/src/pyoperators/iterative/optimize.py
+++ b/src/pyoperators/iterative/optimize.py
@@ -1,6 +1,7 @@
 """
 Wraps scipy.optimize.fmin_* algorithms using Criterion instances.
 """
+
 import numpy as np
 import scipy.optimize as opt
 
diff --git a/src/pyoperators/iterative/stopconditions.py b/src/pyoperators/iterative/stopconditions.py
index bc07e07..d8eed45 100644
--- a/src/pyoperators/iterative/stopconditions.py
+++ b/src/pyoperators/iterative/stopconditions.py
@@ -3,7 +3,6 @@
 
 """
 
-
 __all__ = ['StopCondition', 'MaxErrorStopCondition', 'MaxIterationStopCondition']
 
 
diff --git a/src/pyoperators/utils/fake_MPI.py b/src/pyoperators/utils/fake_MPI.py
index ebcde4a..c88c236 100644
--- a/src/pyoperators/utils/fake_MPI.py
+++ b/src/pyoperators/utils/fake_MPI.py
@@ -1,6 +1,7 @@
 """
 MPI-wrapper module for non-MPI enabled platforms.
 """
+
 import builtins as _builtins
 from itertools import count as _count
 
diff --git a/src/pyoperators/utils/misc.py b/src/pyoperators/utils/misc.py
index edd31f7..8bef7e6 100644
--- a/src/pyoperators/utils/misc.py
+++ b/src/pyoperators/utils/misc.py
@@ -1208,11 +1208,11 @@ def zip_broadcast(*args, **keywords):
         raise TypeError('Invalid keyword(s).')
     iter_str = keywords.get('iter_str', True)
     n = max(
-        1
-        if not isinstance(_, Iterable) or isinstance(_, str) and not iter_str
-        else len(_)
-        if hasattr(_, '__len__')
-        else sys.maxsize
+        (
+            1
+            if not isinstance(_, Iterable) or isinstance(_, str) and not iter_str
+            else len(_) if hasattr(_, '__len__') else sys.maxsize
+        )
         for _ in args
     )