[DataFrame] Inherit documentation from Pandas (#1727)

* Added _inherit_docstrings

* DataFrame documentation inherits from Pandas

* Fix formatting

* Replace hasattr and document properties

* Fix rebase

* Override documentation for groupby

* Override documentation for series

* Don't overwrite property docstrings

* Fix property __doc__ for python2

python/ray/dataframe/dataframe.py

@@ -32,11 +32,13 @@ from .utils import (
     to_pandas,
     _blocks_to_col,
     _blocks_to_row,
-    _create_block_partitions)
+    _create_block_partitions,
+    _inherit_docstrings)
 from . import get_npartitions
 from .index_metadata import _IndexMetadata
 
 
+@_inherit_docstrings(pd.DataFrame)
 class DataFrame(object):
 
     def __init__(self, data=None, index=None, columns=None, dtype=None,

python/ray/dataframe/groupby.py

@@ -2,7 +2,12 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
+import pandas.core.groupby
 
+from .utils import _inherit_docstrings
+
+
+@_inherit_docstrings(pandas.core.groupby.DataFrameGroupBy)
 class DataFrameGroupBy(object):
 
     def __init__(self, partitions, columns, index):

python/ray/dataframe/series.py

@@ -3,6 +3,9 @@ from __future__ import division
 from __future__ import print_function
 
 import numpy as np
+import pandas as pd
+
+from .utils import _inherit_docstrings
 
 
 def na_op():
@@ -11,6 +14,7 @@ def na_op():
     raise NotImplementedError("Not Yet implemented.")
 
 
+@_inherit_docstrings(pd.Series)
 class Series(object):
 
     def __init__(self, series_oids):

python/ray/dataframe/test/test_dataframe.py

@@ -3014,3 +3014,14 @@ def test_iloc(ray_df, pd_df):
     assert ray_df.iloc[1:, 0].equals(pd_df.iloc[1:, 0])
     assert ray_df.iloc[1:2, 0].equals(pd_df.iloc[1:2, 0])
     assert ray_df.iloc[1:2, 0:2].equals(pd_df.iloc[1:2, 0:2])
+
+
+def test__doc__():
+    assert rdf.DataFrame.__doc__ != pd.DataFrame.__doc__
+    assert rdf.DataFrame.__init__ != pd.DataFrame.__init__
+    for attr, obj in rdf.DataFrame.__dict__.items():
+        if (callable(obj) or isinstance(obj, property)) \
+                and attr != "__init__":
+            pd_obj = getattr(pd.DataFrame, attr, None)
+            if callable(pd_obj) or isinstance(pd_obj, property):
+                assert obj.__doc__ == pd_obj.__doc__

python/ray/dataframe/utils.py

@@ -242,3 +242,43 @@ def _blocks_to_row(*partition):
     # columns), this change is needed to ensure correctness.
     row_part.columns = pd.RangeIndex(0, len(row_part.columns))
     return row_part
+
+
+def _inherit_docstrings(parent):
+    """Creates a decorator which overwrites a decorated class' __doc__
+    attribute with parent's __doc__ attribute. Also overwrites __doc__ of
+    methods and properties defined in the class with the __doc__ of matching
+    methods in parent.
+
+    Args:
+        parent (object): Class from which the decorated class inherits __doc__.
+
+    Note:
+        Currently does not override class' __doc__ or __init__'s __doc__.
+
+    Todo:
+        Override the class' __doc__ and __init__'s __doc__  once DataFrame's
+            __init__ method matches pandas.DataFrame's __init__ method.
+
+    Returns:
+        function: decorator which replaces the decorated class' documentation
+            parent's documentation.
+    """
+    def decorator(cls):
+        # cls.__doc__ = parent.__doc__
+        for attr, obj in cls.__dict__.items():
+            if attr == "__init__":
+                continue
+            parent_obj = getattr(parent, attr, None)
+            if not callable(parent_obj) and \
+                    not isinstance(parent_obj, property):
+                continue
+            if callable(obj):
+                obj.__doc__ = parent_obj.__doc__
+            elif isinstance(obj, property) and obj.fget is not None:
+                p = property(obj.fget, obj.fset, obj.fdel, parent_obj.__doc__)
+                setattr(cls, attr, p)
+
+        return cls
+
+    return decorator