Feature/csv dir store

src/power_grid_model_io/data_stores/csv_dir_store.py

@@ -0,0 +1,55 @@
+# SPDX-FileCopyrightText: 2022 Contributors to the Power Grid Model IO project <dynamic.grid.calculation@alliander.com>
+#
+# SPDX-License-Identifier: MPL-2.0
+"""
+CSV Directory Store
+"""
+
+from pathlib import Path
+from typing import Any, Dict, List
+
+import pandas as pd
+
+from power_grid_model_io.data_stores.base_data_store import BaseDataStore
+from power_grid_model_io.data_types import LazyDataFrame, TabularData
+
+
+class CsvDirStore(BaseDataStore[TabularData]):
+    """
+    CSV Directory Store
+
+    The first row of each .csv file is expected to contain the column names, unless specified differently by an
+    extension of this class.
+    """
+
+    __slots__ = ("_dir_path", "_csv_kwargs", "_header_rows")
+
+    def __init__(self, dir_path: Path, **csv_kwargs):
+        super().__init__()
+        self._dir_path = Path(dir_path)
+        self._csv_kwargs: Dict[str, Any] = csv_kwargs
+        self._header_rows: List[int] = [0]
+
+    def load(self) -> TabularData:
+        """
+        Create a lazy loader for all CSV files in a directory and store them in a TabularData instance.
+        """
+
+        def lazy_csv_loader(csv_path: Path) -> LazyDataFrame:
+            def csv_loader():
+                return pd.read_csv(filepath_or_buffer=csv_path, header=self._header_rows, **self._csv_kwargs)
+
+            return csv_loader
+
+        data: Dict[str, LazyDataFrame] = {}
+        for path in self._dir_path.glob("*.csv"):
+            data[path.stem] = lazy_csv_loader(path)
+
+        return TabularData(**data)
+
+    def save(self, data: TabularData) -> None:
+        """
+        Store each table in data as a separate CSV file
+        """
+        for table_name, table_data in data.items():
+            table_data.to_csv(path_or_buf=self._dir_path / f"{table_name}.csv", **self._csv_kwargs)

src/power_grid_model_io/data_stores/excel_file_store.py

@@ -12,8 +12,7 @@
 import pandas as pd
 
 from power_grid_model_io.data_stores.base_data_store import BaseDataStore
-from power_grid_model_io.data_types import TabularData
-from power_grid_model_io.data_types.tabular_data import LazyDataFrame
+from power_grid_model_io.data_types import LazyDataFrame, TabularData
 
 
 class ExcelFileStore(BaseDataStore[TabularData]):

src/power_grid_model_io/data_types/__init__.py

@@ -6,4 +6,4 @@
 """
 
 from power_grid_model_io.data_types._data_types import ExtraInfo, ExtraInfoLookup, StructuredData
-from power_grid_model_io.data_types.tabular_data import TabularData
+from power_grid_model_io.data_types.tabular_data import LazyDataFrame, TabularData

tests/unit/data_stores/test_csv_dir_store.py

@@ -0,0 +1,60 @@
+# SPDX-FileCopyrightText: 2022 Contributors to the Power Grid Model project <dynamic.grid.calculation@alliander.com>
+#
+# SPDX-License-Identifier: MPL-2.0
+
+import tempfile
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pandas as pd
+import pytest
+
+from power_grid_model_io.data_stores.csv_dir_store import CsvDirStore
+from power_grid_model_io.data_types import TabularData
+
+
+@pytest.fixture()
+def temp_dir():
+    with tempfile.TemporaryDirectory() as tmp:
+        yield Path(tmp).resolve()
+
+
+def touch(file_path: Path):
+    open(file_path, "wb").close()
+
+
+@patch("power_grid_model_io.data_stores.csv_dir_store.pd.read_csv")
+def test_load(mock_read_csv: MagicMock, temp_dir: Path):
+    # Arrange
+    foo_data = MagicMock()
+    bar_data = MagicMock()
+    touch(temp_dir / "foo.csv")
+    touch(temp_dir / "bar.csv")
+    mock_read_csv.side_effect = (foo_data, bar_data)
+    csv_dir = CsvDirStore(temp_dir, bla=True)
+
+    # Act
+    csv_data = csv_dir.load()
+
+    # Assert
+    mock_read_csv.assert_not_called()  # The csv data is not yet loaded
+    assert csv_data["foo"] == foo_data
+    assert csv_data["bar"] == bar_data
+    mock_read_csv.assert_any_call(filepath_or_buffer=temp_dir / "foo.csv", header=[0], bla=True)
+    mock_read_csv.assert_any_call(filepath_or_buffer=temp_dir / "bar.csv", header=[0], bla=True)
+
+
+@patch("power_grid_model_io.data_stores.csv_dir_store.pd.DataFrame.to_csv")
+def test_save(mock_to_csv: MagicMock, temp_dir):
+    # Arrange
+    foo_data = pd.DataFrame()
+    bar_data = pd.DataFrame()
+    data = TabularData(foo=foo_data, bar=bar_data)
+    csv_dir = CsvDirStore(temp_dir, bla=True)
+
+    # Act
+    csv_dir.save(data)
+
+    # Assert
+    mock_to_csv.assert_any_call(path_or_buf=temp_dir / "foo.csv", bla=True)
+    mock_to_csv.assert_any_call(path_or_buf=temp_dir / "bar.csv", bla=True)