Merge pull request #7276 from Hakuyume/tabular-helpers

Add `chainer.dataset.tabular.DelegateDataset`

chainer/dataset/tabular/__init__.py

@@ -5,4 +5,5 @@
 from chainer.dataset.tabular import _transform  # NOQA
 from chainer.dataset.tabular import _with_converter  # NOQA
 
+from chainer.dataset.tabular.delegate_dataset import DelegateDataset  # NOQA
 from chainer.dataset.tabular.from_data import from_data  # NOQA

chainer/dataset/tabular/delegate_dataset.py

@@ -0,0 +1,59 @@
+from chainer.dataset.tabular import tabular_dataset
+
+
+class DelegateDataset(tabular_dataset.TabularDataset):
+
+    """A helper class to implement a TabularDataset.
+
+    This class wraps an instance of :class:`~chainer.dataset.TabularDataset`
+    and provides methods of :class:`~chainer.dataset.TabularDataset`.
+    This class is useful to create a custom dataset class by inheriting it.
+
+    >>> import numpy as np
+    >>>
+    >>> from chainer.dataset import tabular
+    >>>
+    >>> class MyDataset(tabular.DelegateDataset):
+    ...
+    ...     def __init__(self):
+    ...         super().__init__(tabular.from_data((
+    ...             ('a', np.arange(10)),
+    ...             ('b', self.get_b),
+    ...             ('c', [3, 1, 4, 5, 9, 2, 6, 8, 7, 0]),
+    ...             (('d', 'e'), self.get_de))))
+    ...
+    ...     def get_b(self, i):
+    ...         return 'b[{}]'.format(i)
+    ...
+    ...     def get_de(self, i):
+    ...         return {'d': 'd[{}]'.format(i), 'e': 'e[{}]'.format(i)}
+    ...
+    >>> dataset = MyDataset()
+    >>> len(dataset)
+    10
+    >>> dataset.keys
+    ('a', 'b', 'c', 'd', 'e')
+    >>> dataset[0]
+    (0, 'b[0]', 3, 'd[0]', 'e[0]')
+
+    Args:
+        dataset (chainer.dataset.TabularDataset): An underlying dataset.
+
+    """
+
+    def __init__(self, dataset):
+        self.dataset = dataset
+
+    def __len__(self):
+        return len(self.dataset)
+
+    @property
+    def keys(self):
+        return self.dataset.keys
+
+    @property
+    def mode(self):
+        return self.dataset.mode
+
+    def get_examples(self, indices, key_indices):
+        return self.dataset.get_examples(indices, key_indices)

docs/source/reference/datasets.rst

@@ -49,6 +49,7 @@ Tabular Dataset Helpers
    :toctree: generated/
    :nosignatures:
 
+   chainer.dataset.tabular.DelegateDataset
    chainer.dataset.tabular.from_data
 
 

tests/chainer_tests/dataset_tests/tabular_tests/test_delegate_dataset.py

@@ -0,0 +1,30 @@
+import unittest
+
+import chainer
+from chainer.dataset import tabular
+from chainer import testing
+
+
+from chainer_tests.dataset_tests.tabular_tests import dummy_dataset
+
+
+@testing.parameterize(
+    {'mode': tuple},
+    {'mode': dict},
+    {'mode': None},
+)
+class TestDelegateDataset(unittest.TestCase):
+
+    def test_delegate_dataset(self):
+        dataset = tabular.DelegateDataset(
+            dummy_dataset.DummyDataset(mode=self.mode))
+
+        self.assertIsInstance(dataset, chainer.dataset.TabularDataset)
+        self.assertEqual(len(dataset), len(dataset.dataset))
+        self.assertEqual(dataset.keys, dataset.dataset.keys)
+        self.assertEqual(dataset.mode, dataset.dataset.mode)
+        self.assertEqual(
+            dataset.get_example(3), dataset.dataset.get_example(3))
+
+
+testing.run_module(__name__, __file__)