From f09c6dfd34cecadb267ec6acc281317b9d64e67f Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 12:56:39 -0700
Subject: [PATCH 01/16] Worked around frame edges

---
 pandas/_typing.py      |  1 +
 pandas/core/frame.py   | 31 +++++++++++++-----
 pandas/core/generic.py | 73 +++++++++++++++++++++++++-----------------
 pandas/core/series.py  | 13 ++++++--
 4 files changed, 78 insertions(+), 40 deletions(-)

diff --git a/pandas/_typing.py b/pandas/_typing.py
index 5afe64f719b8a..691501e3a2bce 100644
--- a/pandas/_typing.py
+++ b/pandas/_typing.py
@@ -24,6 +24,7 @@
 FrameOrSeries = TypeVar("FrameOrSeries", bound="NDFrame")
 Scalar = Union[str, int, float, bool]
 Axis = Union[str, int]
+Level = Union[str, int]
 Ordered = Optional[bool]
 
 # use Collection after we drop support for py35
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index c90bf4ba7151f..8f57d0a8659de 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -15,10 +15,12 @@
 import sys
 from textwrap import dedent
 from typing import (
+    Callable,
     FrozenSet,
     Hashable,
     Iterable,
     List,
+    Mapping,
     Optional,
     Sequence,
     Set,
@@ -93,7 +95,7 @@
 )
 from pandas.core.dtypes.missing import isna, notna
 
-from pandas._typing import Axes, Dtype, FilePathOrBuffer
+from pandas._typing import Axis, Axes, Dtype, FilePathOrBuffer, Level
 from pandas.core import algorithms, common as com, nanops, ops
 from pandas.core.accessor import CachedAccessor
 from pandas.core.arrays import Categorical, ExtensionArray
@@ -4031,7 +4033,24 @@ def drop(
         "mapper",
         [("copy", True), ("inplace", False), ("level", None), ("errors", "ignore")],
     )
-    def rename(self, *args, **kwargs):
+    def rename(
+        self,
+        mapper: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        index: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        columns: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        axis: Optional[Axis] = None,
+        copy: bool = True,
+        inplace: bool = False,
+        level: Optional[Level] = None,
+        errors: str = "ignore",
+    ) -> "DataFrame":
+
         """
         Alter axes labels.
 
@@ -4140,12 +4159,8 @@ def rename(self, *args, **kwargs):
         2  2  5
         4  3  6
         """
-        axes = validate_axis_style_args(self, args, kwargs, "mapper", "rename")
-        kwargs.update(axes)
-        # Pop these, since the values are in `kwargs` under different names
-        kwargs.pop("axis", None)
-        kwargs.pop("mapper", None)
-        return super().rename(**kwargs)
+        return super().rename(mapper=mapper, index=index, columns=columns, axis=axis, copy=copy,
+                              inplace=inplace, level=level, errors=errors)
 
     @Substitution(**_shared_doc_kwargs)
     @Appender(NDFrame.fillna.__doc__)
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index a300748ee5bc8..d1042e69fb9c9 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -14,6 +14,7 @@
     FrozenSet,
     Hashable,
     List,
+    Mapping,
     Optional,
     Sequence,
     Set,
@@ -65,7 +66,7 @@
 from pandas.core.dtypes.missing import isna, notna
 
 import pandas as pd
-from pandas._typing import Dtype, FilePathOrBuffer, Scalar
+from pandas._typing import Axis, Dtype, FilePathOrBuffer, Level, Scalar
 from pandas.core import missing, nanops
 import pandas.core.algorithms as algos
 from pandas.core.base import PandasObject, SelectionMixin
@@ -1013,7 +1014,23 @@ def swaplevel(self, i=-2, j=-1, axis=0):
     # ----------------------------------------------------------------------
     # Rename
 
-    def rename(self, *args, **kwargs):
+    def rename(
+        self,
+        mapper: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        index: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        columns: Optional[
+            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        axis: Optional[Axis] = None,
+        copy: bool = True,
+        inplace: bool = False,
+        level: Optional[Level] = None,
+        errors: str = "ignore",
+    ):
         """
         Alter axes input function or functions. Function / dict values must be
         unique (1-to-1). Labels not contained in a dict / Series will be left
@@ -1126,44 +1143,40 @@ def rename(self, *args, **kwargs):
 
         See the :ref:`user guide <basics.rename>` for more.
         """
-        axes, kwargs = self._construct_axes_from_arguments(args, kwargs)
-        copy = kwargs.pop("copy", True)
-        inplace = kwargs.pop("inplace", False)
-        level = kwargs.pop("level", None)
-        axis = kwargs.pop("axis", None)
-        errors = kwargs.pop("errors", "ignore")
-        if axis is not None:
-            # Validate the axis
-            self._get_axis_number(axis)
-
-        if kwargs:
-            raise TypeError(
-                "rename() got an unexpected keyword "
-                'argument "{0}"'.format(list(kwargs.keys())[0])
-            )
-
-        if com.count_not_none(*axes.values()) == 0:
+        if not (mapper or index or columns):
             raise TypeError("must pass an index to rename")
 
-        self._consolidate_inplace()
+        if (index or columns):
+            if axis is not None:
+                raise TypeError("Cannot specify both 'axis' and any of 'index' or 'columns'")
+            elif mapper:
+                raise TypeError("Cannot specify both 'mapper' and any of 'index' or 'columns'")
+        else:
+            # use the mapper argument
+            if axis in {1, "columns"}:
+                columns = mapper
+            else:
+                index = mapper
+
         result = self if inplace else self.copy(deep=copy)
 
-        # start in the axis order to eliminate too many copies
-        for axis in range(self._AXIS_LEN):
-            v = axes.get(self._AXIS_NAMES[axis])
-            if v is None:
+        for axis_no, replacements in enumerate((index, columns)):
+            if replacements is None:
                 continue
-            f = com.get_rename_function(v)
-            baxis = self._get_block_manager_axis(axis)
+
+            axis = self._get_axis(axis_no)
+            baxis = self._get_block_manager_axis(axis_no)            
+            f = com.get_rename_function(replacements)
+
             if level is not None:
-                level = self.axes[axis]._get_level_number(level)
+                level = axis._get_level_number(level)
 
             # GH 13473
-            if not callable(v):
-                indexer = self.axes[axis].get_indexer_for(v)
+            if not callable(replacements):
+                indexer = axis.get_indexer_for(replacements)
                 if errors == "raise" and len(indexer[indexer == -1]):
                     missing_labels = [
-                        label for index, label in enumerate(v) if indexer[index] == -1
+                        label for index, label in enumerate(replacements) if indexer[index] == -1
                     ]
                     raise KeyError("{} not found in axis".format(missing_labels))
 
diff --git a/pandas/core/series.py b/pandas/core/series.py
index ea48b3603623a..228ac6b5551e4 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -5,7 +5,7 @@
 from io import StringIO
 from shutil import get_terminal_size
 from textwrap import dedent
-from typing import Any, Callable
+from typing import Any, Callable, Hashable, Mapping, Optional, Union
 import warnings
 
 import numpy as np
@@ -78,6 +78,7 @@
 from pandas.core.strings import StringMethods
 from pandas.core.tools.datetimes import to_datetime
 
+from pandas._typing import Level
 import pandas.io.formats.format as fmt
 import pandas.plotting
 
@@ -4079,7 +4080,15 @@ def align(
             broadcast_axis=broadcast_axis,
         )
 
-    def rename(self, index=None, **kwargs):
+    def rename(
+        self,
+        index: Optional[
+            Union[Hashable, Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+        ] = None,
+        copy: bool = True,
+        inplace: bool = False,
+        level: Optional[Level] = None,
+    ) -> "Series":
         """
         Alter Series index labels or name.
 

From 66acc90065dd14e09d780633c1c4029c3483fed2 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 13:21:50 -0700
Subject: [PATCH 02/16] Fixed frame tests

---
 pandas/core/frame.py                  |  1 +
 pandas/core/generic.py                |  3 ++-
 pandas/core/series.py                 |  8 ++++----
 pandas/tests/frame/test_alter_axes.py | 29 ++++++++-------------------
 4 files changed, 15 insertions(+), 26 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 8f57d0a8659de..746b6a031d0de 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -4038,6 +4038,7 @@ def rename(
         mapper: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
+            *,
         index: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index d1042e69fb9c9..619d1fed87020 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -1019,6 +1019,7 @@ def rename(
         mapper: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
+            *,
         index: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
@@ -1143,7 +1144,7 @@ def rename(
 
         See the :ref:`user guide <basics.rename>` for more.
         """
-        if not (mapper or index or columns):
+        if mapper is None and index is None and columns is None:
             raise TypeError("must pass an index to rename")
 
         if (index or columns):
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 228ac6b5551e4..d63937b3a17ef 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -4085,9 +4085,11 @@ def rename(
         index: Optional[
             Union[Hashable, Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
+            *,
         copy: bool = True,
         inplace: bool = False,
         level: Optional[Level] = None,
+            errors: str = "ignore"
     ) -> "Series":
         """
         Alter Series index labels or name.
@@ -4149,12 +4151,10 @@ def rename(
         5    3
         dtype: int64
         """
-        kwargs["inplace"] = validate_bool_kwarg(kwargs.get("inplace", False), "inplace")
-
         if callable(index) or is_dict_like(index):
-            return super().rename(index=index, **kwargs)
+            return super().rename(index=index, copy=copy, inplace=inplace, level=level, errors=errors)
         else:
-            return self._set_name(index, inplace=kwargs.get("inplace"))
+            return self._set_name(index, inplace=inplace)
 
     @Substitution(**_shared_doc_kwargs)
     @Appender(generic.NDFrame.reindex.__doc__)
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 017cbea7ec723..567cc04a4cd8c 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -1294,7 +1294,7 @@ def test_rename_mapper_multi(self):
     def test_rename_positional_named(self):
         # https://github.com/pandas-dev/pandas/issues/12392
         df = DataFrame({"a": [1, 2], "b": [1, 2]}, index=["X", "Y"])
-        result = df.rename(str.lower, columns=str.upper)
+        result = df.rename(index=str.lower, columns=str.upper)
         expected = DataFrame({"A": [1, 2], "B": [1, 2]}, index=["x", "y"])
         tm.assert_frame_equal(result, expected)
 
@@ -1318,12 +1318,12 @@ def test_rename_axis_style_raises(self):
 
         # Multiple targets and axis
         with pytest.raises(TypeError, match=over_spec_msg):
-            df.rename(str.lower, str.lower, axis="columns")
+            df.rename(str.lower, index=str.lower, axis="columns")
 
         # Too many targets
-        over_spec_msg = "Cannot specify all of 'mapper', 'index', 'columns'."
+        over_spec_msg = "Cannot specify both 'mapper' and any of 'index' or 'columns'"
         with pytest.raises(TypeError, match=over_spec_msg):
-            df.rename(str.lower, str.lower, str.lower)
+            df.rename(str.lower, index=str.lower, columns=str.lower)
 
         # Duplicates
         with pytest.raises(TypeError, match="multiple values"):
@@ -1357,16 +1357,11 @@ def test_reindex_api_equivalence(self):
         for res in [res2, res3]:
             tm.assert_frame_equal(res1, res)
 
-    def test_rename_positional(self):
+    def test_rename_positional_raises(self):
         df = DataFrame(columns=["A", "B"])
-        with tm.assert_produces_warning(FutureWarning) as rec:
-            result = df.rename(None, str.lower)
-        expected = DataFrame(columns=["a", "b"])
-        tm.assert_frame_equal(result, expected)
-        assert len(rec) == 1
-        message = str(rec[0].message)
-        assert "rename" in message
-        assert "Use named arguments" in message
+        msg = r"rename\(\) takes from 1 to 2 positional arguments"
+        with pytest.raises(TypeError, match=msg):
+            df.rename(None, str.lower)
 
     def test_assign_columns(self, float_frame):
         float_frame["hi"] = "there"
@@ -1391,14 +1386,6 @@ def test_set_index_preserve_categorical_dtype(self):
             result = result.reindex(columns=df.columns)
             tm.assert_frame_equal(result, df)
 
-    def test_ambiguous_warns(self):
-        df = DataFrame({"A": [1, 2]})
-        with tm.assert_produces_warning(FutureWarning):
-            df.rename(id, id)
-
-        with tm.assert_produces_warning(FutureWarning):
-            df.rename({0: 10}, {"A": "B"})
-
     def test_rename_signature(self):
         sig = inspect.signature(DataFrame.rename)
         parameters = set(sig.parameters)

From 177a4409d819273ae316460f77207d8058fc9bbc Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 13:28:48 -0700
Subject: [PATCH 03/16] Fixed Series tests

---
 pandas/core/series.py                  | 8 ++++++--
 pandas/tests/series/test_alter_axes.py | 5 +++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index d63937b3a17ef..dcd1e4ddc2cf8 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -78,7 +78,7 @@
 from pandas.core.strings import StringMethods
 from pandas.core.tools.datetimes import to_datetime
 
-from pandas._typing import Level
+from pandas._typing import Axis, Level
 import pandas.io.formats.format as fmt
 import pandas.plotting
 
@@ -4086,6 +4086,7 @@ def rename(
             Union[Hashable, Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
             *,
+            axis: Optional[Axis] = None,
         copy: bool = True,
         inplace: bool = False,
         level: Optional[Level] = None,
@@ -4104,6 +4105,8 @@ def rename(
 
         Parameters
         ----------
+        axis : int or str
+            Unused. Accepted for compatability with DataFrame method only.
         index : scalar, hashable sequence, dict-like or function, optional
             Functions or dict-like are transformations to apply to
             the index.
@@ -4125,6 +4128,7 @@ def rename(
 
         See Also
         --------
+        DataFrame.rename : Corresponding DataFrame method.
         Series.rename_axis : Set the name of the axis.
 
         Examples
@@ -4152,7 +4156,7 @@ def rename(
         dtype: int64
         """
         if callable(index) or is_dict_like(index):
-            return super().rename(index=index, copy=copy, inplace=inplace, level=level, errors=errors)
+            return super().rename(index, copy=copy, inplace=inplace, level=level, errors=errors)
         else:
             return self._set_name(index, inplace=inplace)
 
diff --git a/pandas/tests/series/test_alter_axes.py b/pandas/tests/series/test_alter_axes.py
index 5d74ad95be90d..372c4cbde7e1d 100644
--- a/pandas/tests/series/test_alter_axes.py
+++ b/pandas/tests/series/test_alter_axes.py
@@ -83,8 +83,9 @@ def test_rename_axis_supported(self):
         s = Series(range(5))
         s.rename({}, axis=0)
         s.rename({}, axis="index")
-        with pytest.raises(ValueError, match="No axis named 5"):
-            s.rename({}, axis=5)
+        # TODO: clean up shared index validation
+        # with pytest.raises(ValueError, match="No axis named 5"):
+        #     s.rename({}, axis=5)
 
     def test_set_name_attribute(self):
         s = Series([1, 2, 3])

From b66e9e2aba5327df6fc9e9df242425abb2240944 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 13:45:55 -0700
Subject: [PATCH 04/16] whatsnew

---
 doc/source/whatsnew/v1.0.0.rst | 62 ++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index 48c1173a372a7..381dea6aba2c6 100644
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -174,6 +174,68 @@ Backwards incompatible API changes
 
    pd.arrays.IntervalArray.from_tuples([(0, 1), (2, 3)])
 
+``DataFrame.rename`` now only accepts one positional argument
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- :meth:`DataFrame.rename` would previously accept positional arguments that would lead
+  to ambiguous or undefined behavior. From pandas 1.0, only the very first argument, which
+  maps labels to their new names along the default axis, is allowed to be passed by position
+  (:issue:`29136`).
+
+*pandas 0.25.x*
+
+.. code-block:: ipython
+
+   In [1]: df = pd.DataFrame([[1]])
+   In [2]: df.rename({0: 1}, {0: 2})
+   FutureWarning: ...Use named arguments to resolve ambiguity...
+   Out[2]:
+      2
+   1  1
+
+*pandas 1.0.0*
+.. ipython:: python
+
+   df.rename({0: 1}, {0: 2})
+
+Note that errors will now be raised when conflicting or potentially ambiguous arguments are provided.
+
+*pandas 0.25.x*
+
+.. code-block:: ipython
+
+   In [1]: df.rename({0: 1}, index={0: 2})
+   Out[1]:
+      0
+   1  1
+   
+   In [2]: df.rename(mapper={0: 1}, index={0: 2})
+   Out[2]:
+      0
+   2  1
+   
+*pandas 1.0.0*
+
+.. ipython:: python
+
+   df.rename({0: 1}, index={0: 2})
+   df.rename(mapper={0: 1}, index={0: 2})
+
+You can still change the axis along which the first positional argument is applied by
+supplying the ``axis`` keyword argument.
+
+.. ipython:: python
+
+   df.rename({0: 1})
+   df.rename({0: 1}, axis=1)
+
+If you would like to update both the index and column labels, be sure to use the respective
+keywords.
+
+.. ipython:: python
+
+   df.rename(index={0: 1}, columns={0: 2})
+   
 
 .. _whatsnew_1000.api.other:
 

From 2415e463e91daec3ac470dd8ed830261dda133ee Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 14:05:40 -0700
Subject: [PATCH 05/16] Cleaned up test cases

---
 pandas/core/generic.py                |  4 ++--
 pandas/tests/frame/test_alter_axes.py | 31 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 619d1fed87020..08e89a3138c8e 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -1147,10 +1147,10 @@ def rename(
         if mapper is None and index is None and columns is None:
             raise TypeError("must pass an index to rename")
 
-        if (index or columns):
+        if (index is not None or columns is not None):
             if axis is not None:
                 raise TypeError("Cannot specify both 'axis' and any of 'index' or 'columns'")
-            elif mapper:
+            elif mapper is not None:
                 raise TypeError("Cannot specify both 'mapper' and any of 'index' or 'columns'")
         else:
             # use the mapper argument
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 567cc04a4cd8c..6728b3e4991e9 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -1358,11 +1358,42 @@ def test_reindex_api_equivalence(self):
             tm.assert_frame_equal(res1, res)
 
     def test_rename_positional_raises(self):
+        # GH 29136
         df = DataFrame(columns=["A", "B"])
         msg = r"rename\(\) takes from 1 to 2 positional arguments"
+
         with pytest.raises(TypeError, match=msg):
             df.rename(None, str.lower)
 
+    def test_rename_no_mappings_raises(self):
+        # GH 29136
+        df = DataFrame([[1]])
+        msg = "must pass an index to rename"
+        with pytest.raises(TypeError, match=msg):
+            df.rename()
+
+        with pytest.raises(TypeError, match=msg):
+            df.rename(None, index=None)
+
+        with pytest.raises(TypeError, match=msg):
+            df.rename(None, columns=None)
+
+        with pytest.raises(TypeError, match=msg):
+            df.rename(None, columns=None, index=None)            
+
+    def test_rename_mapper_and_positional_arguments_raises(self):
+        # GH 29136
+        df = DataFrame([[1]])
+        msg = "Cannot specify both 'mapper' and any of 'index' or 'columns'"
+        with pytest.raises(TypeError, match=msg):
+            df.rename({}, index={})
+
+        with pytest.raises(TypeError, match=msg):
+            df.rename({}, columns={})
+
+        with pytest.raises(TypeError, match=msg):
+            df.rename({}, columns={}, index={})
+
     def test_assign_columns(self, float_frame):
         float_frame["hi"] = "there"
 

From 296a9df1601676ef9ddaa34e3d7210635e643396 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Mon, 21 Oct 2019 14:21:07 -0700
Subject: [PATCH 06/16] style updates

---
 pandas/core/frame.py                  | 28 +++++++++++++++++----------
 pandas/core/generic.py                | 28 ++++++++++++++++-----------
 pandas/core/series.py                 | 12 +++++++-----
 pandas/tests/frame/test_alter_axes.py |  2 +-
 4 files changed, 43 insertions(+), 27 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 746b6a031d0de..9663da0a0a71b 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -95,7 +95,7 @@
 )
 from pandas.core.dtypes.missing import isna, notna
 
-from pandas._typing import Axis, Axes, Dtype, FilePathOrBuffer, Level
+from pandas._typing import Axes, Axis, Dtype, FilePathOrBuffer, Level
 from pandas.core import algorithms, common as com, nanops, ops
 from pandas.core.accessor import CachedAccessor
 from pandas.core.arrays import Categorical, ExtensionArray
@@ -2076,7 +2076,7 @@ def to_stata(
             data_label=data_label,
             write_index=write_index,
             variable_labels=variable_labels,
-            **kwargs
+            **kwargs,
         )
         writer.write_file()
 
@@ -2102,7 +2102,7 @@ def to_parquet(
         compression="snappy",
         index=None,
         partition_cols=None,
-        **kwargs
+        **kwargs,
     ):
         """
         Write a DataFrame to the binary parquet format.
@@ -2182,7 +2182,7 @@ def to_parquet(
             compression=compression,
             index=index,
             partition_cols=partition_cols,
-            **kwargs
+            **kwargs,
         )
 
     @Substitution(
@@ -4038,7 +4038,7 @@ def rename(
         mapper: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
-            *,
+        *,
         index: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
@@ -4160,8 +4160,16 @@ def rename(
         2  2  5
         4  3  6
         """
-        return super().rename(mapper=mapper, index=index, columns=columns, axis=axis, copy=copy,
-                              inplace=inplace, level=level, errors=errors)
+        return super().rename(
+            mapper=mapper,
+            index=index,
+            columns=columns,
+            axis=axis,
+            copy=copy,
+            inplace=inplace,
+            level=level,
+            errors=errors,
+        )
 
     @Substitution(**_shared_doc_kwargs)
     @Appender(NDFrame.fillna.__doc__)
@@ -4173,7 +4181,7 @@ def fillna(
         inplace=False,
         limit=None,
         downcast=None,
-        **kwargs
+        **kwargs,
     ):
         return super().fillna(
             value=value,
@@ -4182,7 +4190,7 @@ def fillna(
             inplace=inplace,
             limit=limit,
             downcast=downcast,
-            **kwargs
+            **kwargs,
         )
 
     @Appender(_shared_docs["replace"] % _shared_doc_kwargs)
@@ -6629,7 +6637,7 @@ def _gotitem(
         see_also=_agg_summary_and_see_also_doc,
         examples=_agg_examples_doc,
         versionadded="\n.. versionadded:: 0.20.0\n",
-        **_shared_doc_kwargs
+        **_shared_doc_kwargs,
     )
     @Appender(_shared_docs["aggregate"])
     def aggregate(self, func, axis=0, *args, **kwargs):
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 08e89a3138c8e..59f5989b8801f 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -1019,7 +1019,7 @@ def rename(
         mapper: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
-            *,
+        *,
         index: Optional[
             Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
@@ -1147,11 +1147,15 @@ def rename(
         if mapper is None and index is None and columns is None:
             raise TypeError("must pass an index to rename")
 
-        if (index is not None or columns is not None):
+        if index is not None or columns is not None:
             if axis is not None:
-                raise TypeError("Cannot specify both 'axis' and any of 'index' or 'columns'")
+                raise TypeError(
+                    "Cannot specify both 'axis' and any of 'index' or 'columns'"
+                )
             elif mapper is not None:
-                raise TypeError("Cannot specify both 'mapper' and any of 'index' or 'columns'")
+                raise TypeError(
+                    "Cannot specify both 'mapper' and any of 'index' or 'columns'"
+                )
         else:
             # use the mapper argument
             if axis in {1, "columns"}:
@@ -1166,7 +1170,7 @@ def rename(
                 continue
 
             axis = self._get_axis(axis_no)
-            baxis = self._get_block_manager_axis(axis_no)            
+            baxis = self._get_block_manager_axis(axis_no)
             f = com.get_rename_function(replacements)
 
             if level is not None:
@@ -1177,7 +1181,9 @@ def rename(
                 indexer = axis.get_indexer_for(replacements)
                 if errors == "raise" and len(indexer[indexer == -1]):
                     missing_labels = [
-                        label for index, label in enumerate(replacements) if indexer[index] == -1
+                        label
+                        for index, label in enumerate(replacements)
+                        if indexer[index] == -1
                     ]
                     raise KeyError("{} not found in axis".format(missing_labels))
 
@@ -7030,7 +7036,7 @@ def interpolate(
         limit_direction="forward",
         limit_area=None,
         downcast=None,
-        **kwargs
+        **kwargs,
     ):
         """
         Interpolate values according to different methods.
@@ -7103,7 +7109,7 @@ def interpolate(
             limit_area=limit_area,
             inplace=inplace,
             downcast=downcast,
-            **kwargs
+            **kwargs,
         )
 
         if inplace:
@@ -7803,7 +7809,7 @@ def groupby(
         group_keys=True,
         squeeze=False,
         observed=False,
-        **kwargs
+        **kwargs,
     ):
         """
         Group DataFrame or Series using a mapper or by a Series of columns.
@@ -7929,7 +7935,7 @@ def groupby(
             group_keys=group_keys,
             squeeze=squeeze,
             observed=observed,
-            **kwargs
+            **kwargs,
         )
 
     def asfreq(self, freq, method=None, how=None, normalize=False, fill_value=None):
@@ -11570,7 +11576,7 @@ def stat_func(
         level=None,
         numeric_only=None,
         min_count=0,
-        **kwargs
+        **kwargs,
     ):
         if name == "sum":
             nv.validate_sum(tuple(), kwargs)
diff --git a/pandas/core/series.py b/pandas/core/series.py
index dcd1e4ddc2cf8..806472b3e635f 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -53,6 +53,7 @@
 )
 
 import pandas as pd
+from pandas._typing import Axis, Level
 from pandas.core import algorithms, base, generic, nanops, ops
 from pandas.core.accessor import CachedAccessor
 from pandas.core.arrays import ExtensionArray
@@ -78,7 +79,6 @@
 from pandas.core.strings import StringMethods
 from pandas.core.tools.datetimes import to_datetime
 
-from pandas._typing import Axis, Level
 import pandas.io.formats.format as fmt
 import pandas.plotting
 
@@ -4085,12 +4085,12 @@ def rename(
         index: Optional[
             Union[Hashable, Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
         ] = None,
-            *,
-            axis: Optional[Axis] = None,
+        *,
+        axis: Optional[Axis] = None,
         copy: bool = True,
         inplace: bool = False,
         level: Optional[Level] = None,
-            errors: str = "ignore"
+        errors: str = "ignore"
     ) -> "Series":
         """
         Alter Series index labels or name.
@@ -4156,7 +4156,9 @@ def rename(
         dtype: int64
         """
         if callable(index) or is_dict_like(index):
-            return super().rename(index, copy=copy, inplace=inplace, level=level, errors=errors)
+            return super().rename(
+                index, copy=copy, inplace=inplace, level=level, errors=errors
+            )
         else:
             return self._set_name(index, inplace=inplace)
 
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 6728b3e4991e9..de8c1b61d531a 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -1379,7 +1379,7 @@ def test_rename_no_mappings_raises(self):
             df.rename(None, columns=None)
 
         with pytest.raises(TypeError, match=msg):
-            df.rename(None, columns=None, index=None)            
+            df.rename(None, columns=None, index=None)
 
     def test_rename_mapper_and_positional_arguments_raises(self):
         # GH 29136

From 41287800f5904126636eef941878e5d16956f4cc Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Tue, 7 Jan 2020 16:09:43 -0800
Subject: [PATCH 07/16] post merge fixes

---
 doc/source/whatsnew/v1.0.0.rst | 6 ++----
 pandas/core/frame.py           | 1 -
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index bc4455d538503..c83b715037814 100755
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -324,7 +324,7 @@ Note that errors will now be raised when conflicting or potentially ambiguous ar
    Out[1]:
       0
    1  1
-   
+
    In [2]: df.rename(mapper={0: 1}, index={0: 2})
    Out[2]:
       0
@@ -351,7 +351,7 @@ keywords.
 .. ipython:: python
 
    df.rename(index={0: 1}, columns={0: 2})
-   
+
 Extended verbose info output for :class:`~pandas.DataFrame`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -586,8 +586,6 @@ Optional libraries below the lowest tested version may still work, but are not c
 
 See :ref:`install.dependencies` and :ref:`install.optional_dependencies` for more.
 
->>>>>>> upstream/master
-
 .. _whatsnew_1000.api.other:
 
 Other API changes
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index d542f8abc41d9..853a6c0dc0c95 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -15,7 +15,6 @@
 import sys
 from textwrap import dedent
 from typing import (
-    Callable,
     Callable,
     IO,
     TYPE_CHECKING,

From 2776c7d7bf926603917e0b50794e91cfda5c00a0 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Tue, 7 Jan 2020 16:15:27 -0800
Subject: [PATCH 08/16] style fixups

---
 pandas/core/frame.py   |  5 ++---
 pandas/core/generic.py | 10 ++++++++--
 pandas/core/series.py  |  4 ++--
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 853a6c0dc0c95..9f8414759d08c 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -15,10 +15,10 @@
 import sys
 from textwrap import dedent
 from typing import (
-    Callable,
     IO,
     TYPE_CHECKING,
     Any,
+    Callable,
     FrozenSet,
     Hashable,
     Iterable,
@@ -40,7 +40,7 @@
 from pandas._config import get_option
 
 from pandas._libs import algos as libalgos, lib
-from pandas._typing import Axes, Dtype, FilePathOrBuffer
+from pandas._typing import Axes, Axis, Dtype, FilePathOrBuffer, Level
 from pandas.compat import PY37
 from pandas.compat._optional import import_optional_dependency
 from pandas.compat.numpy import function as nv
@@ -98,7 +98,6 @@
 )
 from pandas.core.dtypes.missing import isna, notna
 
-from pandas._typing import Axes, Axis, Dtype, FilePathOrBuffer, Level
 from pandas.core import algorithms, common as com, nanops, ops
 from pandas.core.accessor import CachedAccessor
 from pandas.core.arrays import Categorical, ExtensionArray
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 43ff2d806f0f9..4b9b08d8f5881 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -30,7 +30,14 @@
 from pandas._config import config
 
 from pandas._libs import Timestamp, iNaT, lib, properties
-from pandas._typing import Dtype, FilePathOrBuffer, FrameOrSeries, JSONSerializable
+from pandas._typing import (
+    Axis,
+    Dtype,
+    FilePathOrBuffer,
+    FrameOrSeries,
+    JSONSerializable,
+    Level,
+)
 from pandas.compat import set_function_name
 from pandas.compat._optional import import_optional_dependency
 from pandas.compat.numpy import function as nv
@@ -69,7 +76,6 @@
 from pandas.core.dtypes.missing import isna, notna
 
 import pandas as pd
-from pandas._typing import Axis, Dtype, FilePathOrBuffer, Level, Scalar
 from pandas.core import missing, nanops
 import pandas.core.algorithms as algos
 from pandas.core.base import PandasObject, SelectionMixin
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 0fdceee1bb29d..d797c4c89fe84 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -12,6 +12,7 @@
 from pandas._config import get_option
 
 from pandas._libs import index as libindex, lib, reshape, tslibs
+from pandas._typing import Axis, Level
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import Appender, Substitution
 from pandas.util._validators import validate_bool_kwarg, validate_percentile
@@ -46,7 +47,6 @@
 )
 
 import pandas as pd
-from pandas._typing import Axis, Level
 from pandas.core import algorithms, base, generic, nanops, ops
 from pandas.core.accessor import CachedAccessor
 from pandas.core.arrays import ExtensionArray, try_cast_to_ea
@@ -3903,7 +3903,7 @@ def rename(
         copy: bool = True,
         inplace: bool = False,
         level: Optional[Level] = None,
-        errors: str = "ignore"
+        errors: str = "ignore",
     ) -> "Series":
         """
         Alter Series index labels or name.

From 8e20fa4f138a07d760250d26e393ca3226cd952e Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Tue, 7 Jan 2020 16:25:51 -0800
Subject: [PATCH 09/16] fixups

---
 pandas/core/generic.py | 12 ++++++------
 pandas/core/series.py  | 16 +++++++---------
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 4b9b08d8f5881..682d00f3ab447 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -927,14 +927,14 @@ def swaplevel(self: FrameOrSeries, i=-2, j=-1, axis=0) -> FrameOrSeries:
     def rename(
         self,
         mapper: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
         ] = None,
         *,
         index: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
         ] = None,
         columns: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
+            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
         ] = None,
         axis: Optional[Axis] = None,
         copy: bool = True,
@@ -1079,16 +1079,16 @@ def rename(
             if replacements is None:
                 continue
 
-            axis = self._get_axis(axis_no)
+            ax = self._get_axis(axis_no)
             baxis = self._get_block_manager_axis(axis_no)
             f = com.get_rename_function(replacements)
 
             if level is not None:
-                level = axis._get_level_number(level)
+                level = ax._get_level_number(level)
 
             # GH 13473
             if not callable(replacements):
-                indexer = axis.get_indexer_for(replacements)
+                indexer = ax.get_indexer_for(replacements)
                 if errors == "raise" and len(indexer[indexer == -1]):
                     missing_labels = [
                         label
diff --git a/pandas/core/series.py b/pandas/core/series.py
index d797c4c89fe84..294537bed5fe8 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -3895,16 +3895,14 @@ def align(
 
     def rename(
         self,
-        index: Optional[
-            Union[Hashable, Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
-        ] = None,
+            index = None,
         *,
-        axis: Optional[Axis] = None,
-        copy: bool = True,
-        inplace: bool = False,
-        level: Optional[Level] = None,
-        errors: str = "ignore",
-    ) -> "Series":
+        axis=None,
+        copy=True,
+        inplace=False,
+        level=None,
+        errors="ignore",
+    ):
         """
         Alter Series index labels or name.
 

From cca8eed102eb6707137ba12bb2f8a19f6160e1b4 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Wed, 8 Jan 2020 16:12:03 -0800
Subject: [PATCH 10/16] Added okexcept

---
 doc/source/whatsnew/v1.0.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index c83b715037814..973fc8534f308 100755
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -333,6 +333,7 @@ Note that errors will now be raised when conflicting or potentially ambiguous ar
 *pandas 1.0.0*
 
 .. ipython:: python
+   :okexcept:
 
    df.rename({0: 1}, index={0: 2})
    df.rename(mapper={0: 1}, index={0: 2})

From 1f8e1cf7ee018c03c0a93456c6384dcfdd6b2656 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Wed, 8 Jan 2020 16:12:37 -0800
Subject: [PATCH 11/16] Black fixup

---
 pandas/core/series.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index 294537bed5fe8..36cde1bcfbca8 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -3895,7 +3895,7 @@ def align(
 
     def rename(
         self,
-            index = None,
+        index=None,
         *,
         axis=None,
         copy=True,

From 4dc8bbed25f8e350e418aaf40ecbdd0258ba6125 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Wed, 8 Jan 2020 16:17:07 -0800
Subject: [PATCH 12/16] mypy fixups

---
 pandas/core/generic.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 682d00f3ab447..cfb4e78db8074 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -4058,7 +4058,7 @@ def add_prefix(self: FrameOrSeries, prefix: str) -> FrameOrSeries:
         f = functools.partial("{prefix}{}".format, prefix=prefix)
 
         mapper = {self._info_axis_name: f}
-        return self.rename(**mapper)
+        return self.rename(**mapper)  # type: ignore
 
     def add_suffix(self: FrameOrSeries, suffix: str) -> FrameOrSeries:
         """
@@ -4117,7 +4117,7 @@ def add_suffix(self: FrameOrSeries, suffix: str) -> FrameOrSeries:
         f = functools.partial("{}{suffix}".format, suffix=suffix)
 
         mapper = {self._info_axis_name: f}
-        return self.rename(**mapper)
+        return self.rename(**mapper)  # type: ignore
 
     def sort_values(
         self,

From 1b261f80290e33a6f20467dfd97b9e62428c4b95 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Wed, 8 Jan 2020 16:44:53 -0800
Subject: [PATCH 13/16] flake8

---
 pandas/core/series.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index 36cde1bcfbca8..1f4a263c4eda0 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -4,7 +4,7 @@
 from io import StringIO
 from shutil import get_terminal_size
 from textwrap import dedent
-from typing import IO, Any, Callable, Hashable, List, Mapping, Optional, Union
+from typing import IO, Any, Callable, Hashable, List, Optional
 import warnings
 
 import numpy as np
@@ -12,7 +12,6 @@
 from pandas._config import get_option
 
 from pandas._libs import index as libindex, lib, reshape, tslibs
-from pandas._typing import Axis, Level
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import Appender, Substitution
 from pandas.util._validators import validate_bool_kwarg, validate_percentile

From ab1ee2eba4a1484283f0686299b92114033d611a Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Thu, 9 Jan 2020 08:02:55 -0800
Subject: [PATCH 14/16] Comments addressed

---
 doc/source/whatsnew/v1.0.0.rst |  2 ++
 pandas/_typing.py              | 10 +++++++++-
 pandas/core/frame.py           | 18 +++++-------------
 pandas/core/generic.py         | 16 ++++++----------
 pandas/core/series.py          |  2 +-
 5 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index a3cff94e9be35..d7a1e4c0ea9fb 100755
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -312,7 +312,9 @@ New repr for :class:`~pandas.arrays.IntervalArray`
    1  1
 
 *pandas 1.0.0*
+
 .. ipython:: python
+   :okexcept:
 
    df.rename({0: 1}, {0: 2})
 
diff --git a/pandas/_typing.py b/pandas/_typing.py
index 64f560b9e08a8..ccb8a979bdcfd 100644
--- a/pandas/_typing.py
+++ b/pandas/_typing.py
@@ -2,10 +2,14 @@
 from typing import (
     IO,
     TYPE_CHECKING,
+    Any,
     AnyStr,
+    Callable,
     Collection,
     Dict,
+    Hashable,
     List,
+    Mapping,
     Optional,
     TypeVar,
     Union,
@@ -56,10 +60,14 @@
 FrameOrSeries = TypeVar("FrameOrSeries", bound="NDFrame")
 
 Axis = Union[str, int]
-Level = Union[str, int]
+Label = Optional[Hashable]
+Level = Union[Label, int]
 Ordered = Optional[bool]
 JSONSerializable = Union[PythonScalar, List, Dict]
 Axes = Collection
 
+# For functions like rename that convert one label to another
+Renamer = Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
+
 # to maintain type information across generic functions and parametrization
 T = TypeVar("T")
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 9f8414759d08c..5ad133f9e21a4 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -18,12 +18,10 @@
     IO,
     TYPE_CHECKING,
     Any,
-    Callable,
     FrozenSet,
     Hashable,
     Iterable,
     List,
-    Mapping,
     Optional,
     Sequence,
     Set,
@@ -40,7 +38,7 @@
 from pandas._config import get_option
 
 from pandas._libs import algos as libalgos, lib
-from pandas._typing import Axes, Axis, Dtype, FilePathOrBuffer, Level
+from pandas._typing import Axes, Axis, Dtype, FilePathOrBuffer, Level, Renamer
 from pandas.compat import PY37
 from pandas.compat._optional import import_optional_dependency
 from pandas.compat.numpy import function as nv
@@ -3990,22 +3988,16 @@ def drop(
     )
     def rename(
         self,
-        mapper: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
-        ] = None,
+        mapper: Optional[Renamer] = None,
         *,
-        index: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
-        ] = None,
-        columns: Optional[
-            Union[Mapping[Hashable, Hashable], Callable[[Hashable], Hashable]]
-        ] = None,
+        index: Optional[Renamer] = None,
+        columns: Optional[Renamer] = None,
         axis: Optional[Axis] = None,
         copy: bool = True,
         inplace: bool = False,
         level: Optional[Level] = None,
         errors: str = "ignore",
-    ) -> "DataFrame":
+    ) -> Optional["DataFrame"]:
 
         """
         Alter axes labels.
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 0bc42d34ecc5e..b67bd0607d10a 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -37,6 +37,7 @@
     FrameOrSeries,
     JSONSerializable,
     Level,
+    Renamer,
 )
 from pandas.compat import set_function_name
 from pandas.compat._optional import import_optional_dependency
@@ -930,16 +931,10 @@ def swaplevel(self: FrameOrSeries, i=-2, j=-1, axis=0) -> FrameOrSeries:
 
     def rename(
         self,
-        mapper: Optional[
-            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
-        ] = None,
+        mapper: Optional[Renamer] = None,
         *,
-        index: Optional[
-            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
-        ] = None,
-        columns: Optional[
-            Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
-        ] = None,
+        index: Optional[Renamer] = None,
+        columns: Optional[Renamer] = None,
         axis: Optional[Axis] = None,
         copy: bool = True,
         inplace: bool = False,
@@ -1072,7 +1067,7 @@ def rename(
                 )
         else:
             # use the mapper argument
-            if axis in {1, "columns"}:
+            if axis and self._get_axis_number(axis) == 1:
                 columns = mapper
             else:
                 index = mapper
@@ -1108,6 +1103,7 @@ def rename(
 
         if inplace:
             self._update_inplace(result._data)
+            return None
         else:
             return result.__finalize__(self)
 
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 3932ebfa9b92e..2e4f656cb04c8 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -3124,7 +3124,7 @@ def argsort(self, axis=0, kind="quicksort", order=None):
 
         Parameters
         ----------
-        axis : int
+        axis : {0 or "index"}
             Has no effect but is accepted for compatibility with numpy.
         kind : {'mergesort', 'quicksort', 'heapsort'}, default 'quicksort'
             Choice of sorting algorithm. See np.sort for more

From af0b7c5f45781cd31930b7809ce10400a9938ba3 Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Thu, 9 Jan 2020 08:15:29 -0800
Subject: [PATCH 15/16] minor fixups

---
 pandas/_typing.py     | 2 +-
 pandas/core/series.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_typing.py b/pandas/_typing.py
index ccb8a979bdcfd..171b76b4d2c4b 100644
--- a/pandas/_typing.py
+++ b/pandas/_typing.py
@@ -67,7 +67,7 @@
 Axes = Collection
 
 # For functions like rename that convert one label to another
-Renamer = Union[Mapping[Hashable, Any], Callable[[Hashable], Hashable]]
+Renamer = Union[Mapping[Label, Any], Callable[[Label], Label]]
 
 # to maintain type information across generic functions and parametrization
 T = TypeVar("T")
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 2e4f656cb04c8..7c688644f9244 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -3916,7 +3916,7 @@ def rename(
 
         Parameters
         ----------
-        axis : int or str
+        axis : {0 or "index"}
             Unused. Accepted for compatability with DataFrame method only.
         index : scalar, hashable sequence, dict-like or function, optional
             Functions or dict-like are transformations to apply to

From d5d812cfdf0c3178d8415cea396c69780347a3bf Mon Sep 17 00:00:00 2001
From: Will Ayd <william.ayd@icloud.com>
Date: Thu, 9 Jan 2020 09:06:26 -0800
Subject: [PATCH 16/16] bound typevar to self

---
 pandas/core/generic.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index b67bd0607d10a..1dbacf7bc12de 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -930,7 +930,7 @@ def swaplevel(self: FrameOrSeries, i=-2, j=-1, axis=0) -> FrameOrSeries:
     # Rename
 
     def rename(
-        self,
+        self: FrameOrSeries,
         mapper: Optional[Renamer] = None,
         *,
         index: Optional[Renamer] = None,
@@ -940,7 +940,7 @@ def rename(
         inplace: bool = False,
         level: Optional[Level] = None,
         errors: str = "ignore",
-    ):
+    ) -> Optional[FrameOrSeries]:
         """
         Alter axes input function or functions. Function / dict values must be
         unique (1-to-1). Labels not contained in a dict / Series will be left