Implement CSVHandler

sdv/io/local/__init__.py

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+"""Local I/O module."""
+
+from sdv.io.local.local import BaseLocalHandler, CSVHandler
+
+__all__ = (
+    'BaseLocalHandler',
+    'CSVHandler'
+)

sdv/io/local/local.py

@@ -0,0 +1,194 @@
+"""Local file handlers."""
+import codecs
+import inspect
+import os
+from pathlib import Path
+
+import pandas as pd
+
+from sdv.metadata import MultiTableMetadata
+
+
+class BaseLocalHandler:
+    """Base class for local handlers."""
+
+    def __init__(self, decimal='.', float_format=None):
+        self.decimal = decimal
+        self.float_format = float_format
+
+    def _infer_metadata(self, data):
+        """Detect the metadata for all tables in a dictionary of dataframes.
+
+        Args:
+            data (dict):
+                Dictionary of table names to dataframes.
+
+        Returns:
+            MultiTableMetadata:
+                An ``sdv.metadata.MultiTableMetadata`` object with the detected metadata
+                properties from the data.
+        """
+        metadata = MultiTableMetadata()
+        metadata.detect_from_dataframes(data)
+        return metadata
+
+    def read(self):
+        """Read data from files and returns it along with metadata.
+
+        This method must be implemented by subclasses.
+
+        Returns:
+            tuple:
+                A tuple containing the read data as a dictionary and metadata. The dictionary maps
+                table names to pandas DataFrames. The metadata is an object describing the data.
+        """
+        raise NotImplementedError()
+
+    def write(self):
+        """Write data to files.
+
+        This method must be implemented by subclasses.
+        """
+        raise NotImplementedError()
+
+
+class CSVHandler(BaseLocalHandler):
+    """A class for handling CSV files.
+
+    Args:
+        sep (str):
+            The separator used for reading and writing CSV files. Defaults to ``,``.
+        encoding (str):
+            The character encoding to use for reading and writing CSV files. Defaults to ``UTF``.
+        decimal (str):
+            The character used to denote the decimal point. Defaults to ``.``.
+        float_format (str or None):
+            The formatting string for floating-point numbers. Optional.
+        quotechar (str):
+            Character used to denote the start and end of a quoted item.
+            Quoted items can include the delimiter and it will be ignored. Defaults to '"'.
+        quoting (int or None):
+            Control field quoting behavior. Default is 0.
+
+    Raises:
+        ValueError:
+            If the provided encoding is not available in the system.
+    """
+
+    def __init__(self, sep=',', encoding='UTF', decimal='.', float_format=None,
+                 quotechar='"', quoting=0):
+        super().__init__(decimal, float_format)
+        try:
+            codecs.lookup(encoding)
+        except LookupError as error:
+            raise ValueError(
+                f"The provided encoding '{encoding}' is not available in your system."
+            ) from error
+
+        self.sep = sep
+        self.encoding = encoding
+        self.quotechar = quotechar
+        self.quoting = quoting
+
+    def read(self, folder_name, file_names=None):
+        """Read data from CSV files and returns it along with metadata.
+
+        Args:
+            folder_name (str):
+                The name of the folder containing CSV files.
+            file_names (list of str, optional):
+                The names of CSV files to read. If None, all files ending with '.csv'
+                in the folder are read.
+
+        Returns:
+            tuple:
+                A tuple containing the data as a dictionary and metadata. The dictionary maps
+                table names to pandas DataFrames. The metadata is an object describing the data.
+
+        Raises:
+            FileNotFoundError:
+                If the specified files do not exist in the folder.
+        """
+        data = {}
+        metadata = MultiTableMetadata()
+
+        folder_path = Path(folder_name)
+
+        if file_names is None:
+            # If file_names is None, read all files in the folder ending with ".csv"
+            file_paths = folder_path.glob('*.csv')
+        else:
+            # Validate if the given files exist in the folder
+            file_names = file_names
+            missing_files = [
+                file
+                for file in file_names
+                if not (folder_path / file).exists()
+            ]
+            if missing_files:
+                raise FileNotFoundError(
+                    f"The following files do not exist in the folder: {', '.join(missing_files)}."
+                )
+
+            file_paths = [folder_path / file for file in file_names]
+
+        # Read CSV files
+        kwargs = {
+            'sep': self.sep,
+            'encoding': self.encoding,
+            'parse_dates': False,
+            'low_memory': False,
+            'decimal': self.decimal,
+            'on_bad_lines': 'warn',
+            'quotechar': self.quotechar,
+            'quoting': self.quoting
+        }
+
+        args = inspect.getfullargspec(pd.read_csv)
+        if 'on_bad_lines' not in args.kwonlyargs:
+            kwargs.pop('on_bad_lines')
+            kwargs['error_bad_lines'] = False
+
+        for file_path in file_paths:
+            table_name = file_path.stem  # Remove file extension to get table name
+            data[table_name] = pd.read_csv(
+                file_path,
+                **kwargs
+            )
+
+        metadata = self._infer_metadata(data)
+        return data, metadata
+
+    def write(self, synthetic_data, folder_name, file_name_suffix=None, mode='x'):
+        """Write synthetic data to CSV files.
+
+        Args:
+            synthetic_data (dict):
+                A dictionary mapping table names to pandas DataFrames containing synthetic data.
+            folder_name (str):
+                The name of the folder to write CSV files to.
+            file_name_suffix (str, optional):
+                An optional suffix to add to each file name. If ``None``, no suffix is added.
+            mode (str, optional):
+                The mode of writing to use. Defaults to 'x'.
+                'x': Write to new files, raising errors if existing files exist with the same name.
+                'w': Write to new files, clearing any existing files that exist.
+                'a': Append the new CSV rows to any existing files.
+        """
+        folder_path = Path(folder_name)
+        if not os.path.exists(folder_path):
+            os.makedirs(folder_path)
+
+        for table_name, table_data in synthetic_data.items():
+            file_name = f'{table_name}{file_name_suffix}' if file_name_suffix else f'{table_name}'
+            file_path = f'{folder_path / file_name}.csv'
+            table_data.to_csv(
+                file_path,
+                sep=self.sep,
+                encoding=self.encoding,
+                index=False,
+                float_format=self.float_format,
+                quotechar=self.quotechar,
+                quoting=self.quoting,
+                mode=mode,
+            )

tests/integration/io/local/test_local.py

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+import pandas as pd
+
+from sdv.io.local import CSVHandler
+from sdv.metadata import MultiTableMetadata
+
+
+class TestCSVHandler:
+
+    def test_integration_read_write(self, tmpdir):
+        """Test end to end the read and write methods of ``CSVHandler``."""
+        # Prepare synthetic data
+        synthetic_data = {
+            'table1': pd.DataFrame({'col1': [1, 2, 3], 'col2': ['a', 'b', 'c']}),
+            'table2': pd.DataFrame({'col3': [4, 5, 6], 'col4': ['d', 'e', 'f']})
+        }
+
+        # Write synthetic data to CSV files
+        handler = CSVHandler()
+        handler.write(synthetic_data, tmpdir)
+
+        # Read data from CSV files
+        data, metadata = handler.read(tmpdir)
+
+        # Check if data was read correctly
+        assert len(data) == 2
+        assert 'table1' in data
+        assert 'table2' in data
+        assert isinstance(metadata, MultiTableMetadata) is True
+
+        # Check if the dataframes match the original synthetic data
+        pd.testing.assert_frame_equal(data['table1'], synthetic_data['table1'])
+        pd.testing.assert_frame_equal(data['table2'], synthetic_data['table2'])