From 05efc5120f34bdb1cc3f6a7716c8b26d39b98d08 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Tue, 24 Oct 2017 12:59:39 -0500
Subject: [PATCH 01/12] BUG/REF: Handle ambiguous rename

---
 pandas/core/frame.py                          | 69 ++++++++++++++++---
 pandas/core/generic.py                        | 45 ------------
 pandas/tests/frame/test_alter_axes.py         | 11 +++
 .../tests/frame/test_axis_select_reindex.py   | 16 ++---
 4 files changed, 78 insertions(+), 63 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 5ad82d0da95fa..36e481f255d5b 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -2917,12 +2917,12 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
                                             broadcast_axis=broadcast_axis)
 
     @Appender(_shared_docs['reindex'] % _shared_doc_kwargs)
-    def reindex(self, labels=None, index=None, columns=None, axis=None,
-                **kwargs):
-        axes = self._validate_axis_style_args(labels, 'labels',
-                                              axes=[index, columns],
-                                              axis=axis, method_name='reindex')
+    def reindex(self, *args, **kwargs):
+        axes = self._validate_axis_style_args(args, kwargs, 'labels',
+                                              'reindex')
         kwargs.update(axes)
+        kwargs.pop('axis', None)
+        kwargs.pop('labels', None)
         return super(DataFrame, self).reindex(**kwargs)
 
     @Appender(_shared_docs['reindex_axis'] % _shared_doc_kwargs)
@@ -2933,8 +2933,7 @@ def reindex_axis(self, labels, axis=0, method=None, level=None, copy=True,
                                         method=method, level=level, copy=copy,
                                         limit=limit, fill_value=fill_value)
 
-    def rename(self, mapper=None, index=None, columns=None, axis=None,
-               **kwargs):
+    def rename(self, *args, **kwargs):
         """Alter axes labels.
 
         Function / dict values must be unique (1-to-1). Labels not contained in
@@ -3008,10 +3007,9 @@ def rename(self, mapper=None, index=None, columns=None, axis=None,
         2  2  5
         4  3  6
         """
-        axes = self._validate_axis_style_args(mapper, 'mapper',
-                                              axes=[index, columns],
-                                              axis=axis, method_name='rename')
+        axes = self._validate_axis_style_args(args, kwargs, 'mapper', 'rename')
         kwargs.update(axes)
+        kwargs.pop('axis', None)
         return super(DataFrame, self).rename(**kwargs)
 
     @Appender(_shared_docs['fillna'] % _shared_doc_kwargs)
@@ -3027,6 +3025,57 @@ def shift(self, periods=1, freq=None, axis=0):
         return super(DataFrame, self).shift(periods=periods, freq=freq,
                                             axis=axis)
 
+    def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
+        out = {}
+        # Goal: fill out with index/columns-style arguments
+        # like out = {'index': foo, 'columns': bar}
+        # Start by validaing for consistency
+        if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
+            msg = "Cannot specify both 'axis' and any of 'columns' or 'index'."
+            raise TypeError(msg)
+
+        # Start with explicit values provided by the user...
+        if arg_name in kwargs:
+            if args:
+                msg = "{} got multiple values for argument '{}'".format(
+                    method_name, arg_name)
+                raise TypeError(msg)
+            axis = self._get_axis_name(kwargs.get('axis', 0))
+            out[axis] = kwargs[arg_name]
+
+        # fill in axes
+        for k, v in kwargs.items():
+            try:
+                ax = self._get_axis_name(k)
+            except ValueError:
+                pass
+            else:
+                out[ax] = v
+
+        # All user-provided kwargs have been handled now.
+        # Now we supplement with positional arguments, raising when there's
+        # ambiguity
+
+        if len(args) == 0:
+            pass  # validate later
+        elif len(args) == 1:
+            axis = self._get_axis_name(kwargs.get('axis', 0))
+            out[axis] = args[0]
+        elif len(args) == 2:
+            if 'axis' in kwargs:
+                msg = "Cannot specify both {} and any of 'index' or 'columns'"
+                raise TypeError(msg.format(arg_name))
+            msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
+                   "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
+                   "arguments to remove any ambiguity.")
+            warnings.warn(msg.format(method_name=method_name,), stacklevel=3)
+            out[self._AXIS_NAMES[0]] = args[0]
+            out[self._AXIS_NAMES[1]] = args[1]
+        else:
+            msg = "Cannot specify all of '{}', 'index', 'columns'."
+            raise TypeError(msg.format(arg_name))
+        return out
+
     def set_index(self, keys, drop=True, append=False, inplace=False,
                   verify_integrity=False):
         """
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 3e5828fc59932..0bd64d491537c 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -728,51 +728,6 @@ def swaplevel(self, i=-2, j=-1, axis=0):
         result._data.set_axis(axis, labels.swaplevel(i, j))
         return result
 
-    def _validate_axis_style_args(self, arg, arg_name, axes,
-                                  axis, method_name):
-        out = {}
-        for i, value in enumerate(axes):
-            if value is not None:
-                out[self._AXIS_NAMES[i]] = value
-
-        aliases = ', '.join(self._AXIS_NAMES.values())
-        if axis is not None:
-            # Using "axis" style, along with a positional arg
-            # Both index and columns should be None then
-            axis = self._get_axis_name(axis)
-            if any(x is not None for x in axes):
-                msg = (
-                    "Can't specify both 'axis' and {aliases}. "
-                    "Specify either\n"
-                    "\t.{method_name}({arg_name}, axis=axis), or\n"
-                    "\t.{method_name}(index=index, columns=columns)"
-                ).format(arg_name=arg_name, method_name=method_name,
-                         aliases=aliases)
-                raise TypeError(msg)
-            out[axis] = arg
-
-        elif _all_not_none(arg, *axes):
-            msg = (
-                "Cannot specify all of '{arg_name}', {aliases}. "
-                "Specify either {arg_name} and 'axis', or {aliases}."
-            ).format(arg_name=arg_name, aliases=aliases)
-            raise TypeError(msg)
-
-        elif _all_not_none(arg, axes[0]):
-            # This is the "ambiguous" case, so emit a warning
-            msg = (
-                "Interpreting call to '.{method_name}(a, b)' as "
-                "'.{method_name}(index=a, columns=b)'. "  # TODO
-                "Use keyword arguments to remove any ambiguity."
-            ).format(method_name=method_name)
-            warnings.warn(msg, stacklevel=3)
-            out[self._AXIS_ORDERS[0]] = arg
-            out[self._AXIS_ORDERS[1]] = axes[0]
-        elif axes[0] is None:
-            # This is for the default axis, like reindex([0, 1])
-            out[self._AXIS_ORDERS[0]] = arg
-        return out
-
     # ----------------------------------------------------------------------
     # Rename
 
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 84f7dd108f2cb..cf37890c423e1 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -956,6 +956,17 @@ def test_reindex_api_equivalence(self):
         for res in [res2, res3]:
             tm.assert_frame_equal(res1, res)
 
+    def test_rename_positional(self):
+        df = pd.DataFrame(columns=['A', 'B'])
+        with tm.assert_produces_warning(UserWarning) as rec:
+            result = df.rename(None, str.lower)
+        expected = pd.DataFrame(columns=['a', 'b'])
+        assert_frame_equal(result, expected)
+        assert len(rec) == 1
+        message = str(rec[0].message)
+        assert 'rename' in message
+        assert 'Use named arguments' in message
+
     def test_assign_columns(self):
         self.frame['hi'] = 'there'
 
diff --git a/pandas/tests/frame/test_axis_select_reindex.py b/pandas/tests/frame/test_axis_select_reindex.py
index bf96818edf04e..ebfc8fb3f21e3 100644
--- a/pandas/tests/frame/test_axis_select_reindex.py
+++ b/pandas/tests/frame/test_axis_select_reindex.py
@@ -476,32 +476,32 @@ def test_reindex_positional_warns(self):
     def test_reindex_axis_style_raises(self):
         # https://github.com/pandas-dev/pandas/issues/12392
         df = pd.DataFrame({"A": [1, 2, 3], 'B': [4, 5, 6]})
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, 'Cannot specify both labels'):
             df.reindex([0, 1], ['A'], axis=1)
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, 'Cannot specify both labels'):
             df.reindex([0, 1], ['A'], axis='index')
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], axis='index')
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], axis='columns')
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(columns=[0, 1], axis='columns')
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], columns=[0, 1], axis='columns')
 
         with tm.assert_raises_regex(TypeError, 'Cannot specify all'):
             df.reindex([0, 1], [0], ['A'])
 
         # Mixing styles
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], axis='index')
 
-        with tm.assert_raises_regex(TypeError, 'reindex'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], axis='columns')
 
     def test_reindex_single_named_indexer(self):

From 7c419e0fa6a9f74dd25697e3413067a0310798a3 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Tue, 24 Oct 2017 13:12:50 -0500
Subject: [PATCH 02/12] Do for panel too

---
 pandas/core/frame.py   | 51 ------------------------------------------
 pandas/core/generic.py | 51 ++++++++++++++++++++++++++++++++++++++++++
 pandas/core/panel.py   | 31 ++++++++++++++++---------
 3 files changed, 72 insertions(+), 61 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 36e481f255d5b..869880274a7c9 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -3025,57 +3025,6 @@ def shift(self, periods=1, freq=None, axis=0):
         return super(DataFrame, self).shift(periods=periods, freq=freq,
                                             axis=axis)
 
-    def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
-        out = {}
-        # Goal: fill out with index/columns-style arguments
-        # like out = {'index': foo, 'columns': bar}
-        # Start by validaing for consistency
-        if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
-            msg = "Cannot specify both 'axis' and any of 'columns' or 'index'."
-            raise TypeError(msg)
-
-        # Start with explicit values provided by the user...
-        if arg_name in kwargs:
-            if args:
-                msg = "{} got multiple values for argument '{}'".format(
-                    method_name, arg_name)
-                raise TypeError(msg)
-            axis = self._get_axis_name(kwargs.get('axis', 0))
-            out[axis] = kwargs[arg_name]
-
-        # fill in axes
-        for k, v in kwargs.items():
-            try:
-                ax = self._get_axis_name(k)
-            except ValueError:
-                pass
-            else:
-                out[ax] = v
-
-        # All user-provided kwargs have been handled now.
-        # Now we supplement with positional arguments, raising when there's
-        # ambiguity
-
-        if len(args) == 0:
-            pass  # validate later
-        elif len(args) == 1:
-            axis = self._get_axis_name(kwargs.get('axis', 0))
-            out[axis] = args[0]
-        elif len(args) == 2:
-            if 'axis' in kwargs:
-                msg = "Cannot specify both {} and any of 'index' or 'columns'"
-                raise TypeError(msg.format(arg_name))
-            msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
-                   "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
-                   "arguments to remove any ambiguity.")
-            warnings.warn(msg.format(method_name=method_name,), stacklevel=3)
-            out[self._AXIS_NAMES[0]] = args[0]
-            out[self._AXIS_NAMES[1]] = args[1]
-        else:
-            msg = "Cannot specify all of '{}', 'index', 'columns'."
-            raise TypeError(msg.format(arg_name))
-        return out
-
     def set_index(self, keys, drop=True, append=False, inplace=False,
                   verify_integrity=False):
         """
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 0bd64d491537c..6e4a7721fc9a9 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -2777,6 +2777,57 @@ def sort_index(self, axis=0, level=None, ascending=True, inplace=False,
         new_axis = labels.take(sort_index)
         return self.reindex(**{axis_name: new_axis})
 
+    def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
+        out = {}
+        # Goal: fill out with index/columns-style arguments
+        # like out = {'index': foo, 'columns': bar}
+        # Start by validaing for consistency
+        if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
+            msg = "Cannot specify both 'axis' and any of 'columns' or 'index'."
+            raise TypeError(msg)
+
+        # Start with explicit values provided by the user...
+        if arg_name in kwargs:
+            if args:
+                msg = "{} got multiple values for argument '{}'".format(
+                    method_name, arg_name)
+                raise TypeError(msg)
+            axis = self._get_axis_name(kwargs.get('axis', 0))
+            out[axis] = kwargs[arg_name]
+
+        # fill in axes
+        for k, v in kwargs.items():
+            try:
+                ax = self._get_axis_name(k)
+            except ValueError:
+                pass
+            else:
+                out[ax] = v
+
+        # All user-provided kwargs have been handled now.
+        # Now we supplement with positional arguments, raising when there's
+        # ambiguity
+
+        if len(args) == 0:
+            pass  # validate later
+        elif len(args) == 1:
+            axis = self._get_axis_name(kwargs.get('axis', 0))
+            out[axis] = args[0]
+        elif len(args) == 2:
+            if 'axis' in kwargs:
+                msg = "Cannot specify both {} and any of 'index' or 'columns'"
+                raise TypeError(msg.format(arg_name))
+            msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
+                   "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
+                   "arguments to remove any ambiguity.")
+            warnings.warn(msg.format(method_name=method_name,), stacklevel=3)
+            out[self._AXIS_NAMES[0]] = args[0]
+            out[self._AXIS_NAMES[1]] = args[1]
+        else:
+            msg = "Cannot specify all of '{}', 'index', 'columns'."
+            raise TypeError(msg.format(arg_name))
+        return out
+
     _shared_docs['reindex'] = """
         Conform %(klass)s to new index with optional filling logic, placing
         NA/NaN in locations having no value in the previous index. A new object
diff --git a/pandas/core/panel.py b/pandas/core/panel.py
index 997dd9c8e0f67..77e706d9dcf49 100644
--- a/pandas/core/panel.py
+++ b/pandas/core/panel.py
@@ -1199,20 +1199,31 @@ def _wrap_result(self, result, axis):
         return self._construct_return_type(result, axes)
 
     @Appender(_shared_docs['reindex'] % _shared_doc_kwargs)
-    def reindex(self, labels=None,
-                items=None, major_axis=None, minor_axis=None,
-                axis=None, **kwargs):
-        major_axis = (major_axis if major_axis is not None else
-                      kwargs.pop('major', None))
-        minor_axis = (minor_axis if minor_axis is not None else
-                      kwargs.pop('minor', None))
-        axes = self._validate_axis_style_args(
-            labels, 'labels', axes=[items, major_axis, minor_axis],
-            axis=axis, method_name='reindex')
+    def reindex(self, *args, **kwargs):
+        major = kwargs.pop("major", None)
+        minor = kwargs.pop('minor', None)
+
+        if major is not None:
+            if kwargs.get("major_axis"):
+                raise TypeError("Cannot specify both 'major' and 'major_axis'")
+            kwargs['major_axis'] = major
+        if minor is not None:
+            if kwargs.get("minor_axis"):
+                raise TypeError("Cannot specify both 'minor' and 'minor_axis'")
+
+            kwargs['minor_axis'] = minor
+        # major_axis = (major_axis if major_axis is not None else
+        #               kwargs.pop('major', None))
+        # minor_axis = (minor_axis if minor_axis is not None else
+        #               kwargs.pop('minor', None))
+        axes = self._validate_axis_style_args(args, kwargs, 'labels',
+                                              'reindex')
         if self.ndim >= 4:
             # Hack for PanelND
             axes = {}
         kwargs.update(axes)
+        kwargs.pop('axis', None)
+        kwargs.pop('labels', None)
         return super(Panel, self).reindex(**kwargs)
 
     @Appender(_shared_docs['rename'] % _shared_doc_kwargs)

From fbf246bbb8a8403833cd6e94f36861f83be52fcd Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Tue, 24 Oct 2017 13:54:22 -0500
Subject: [PATCH 03/12] For panel4d

---
 pandas/core/panel4d.py | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/pandas/core/panel4d.py b/pandas/core/panel4d.py
index e6914fb268359..ba5853117b38e 100644
--- a/pandas/core/panel4d.py
+++ b/pandas/core/panel4d.py
@@ -1,6 +1,7 @@
 """ Panel4D: a 4-d dict like collection of panels """
 
 import warnings
+from pandas.core.generic import NDFrame
 from pandas.core.panelnd import create_nd_panel_factory
 from pandas.core.panel import Panel
 
@@ -62,12 +63,34 @@ def panel4d_reindex(self, labs=None, labels=None, items=None, major_axis=None,
     # Hack for reindex_axis deprecation
     # Ha, we used labels for two different things
     # I think this will work still.
-    axes = self._validate_axis_style_args(
-        labs, 'labels',
-        axes=[labels, items, major_axis, minor_axis],
-        axis=axis, method_name='reindex')
+    if labs is None:
+        args = ()
+    else:
+        args = (labs,)
+    kwargs_ = dict(labels=labels,
+                   items=items,
+                   major_axis=major_axis,
+                   minor_axis=minor_axis,
+                   axis=axis)
+    kwargs_ = {k: v for k, v in kwargs_.items() if v is not None}
+    # major = kwargs.pop("major", None)
+    # minor = kwargs.pop('minor', None)
+
+    # if major is not None:
+    #     if kwargs.get("major_axis"):
+    #         raise TypeError("Cannot specify both 'major' and 'major_axis'")
+    #     kwargs_['major_axis'] = major
+    # if minor is not None:
+    #     if kwargs.get("minor_axis"):
+    #         raise TypeError("Cannot specify both 'minor' and 'minor_axis'")
+    #     kwargs_['minor_axis'] = minor
+
+    if axis is not None:
+        kwargs_['axis'] = axis
+
+    axes = self._validate_axis_style_args(args, kwargs_, 'labs', 'reindex')
     kwargs.update(axes)
-    return super(Panel, self).reindex(**kwargs)
+    return NDFrame.reindex(self, **kwargs)
 
 
 Panel4D.__init__ = panel4d_init

From ef77ca13f0c4953a525a48495cdba44913814712 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Tue, 24 Oct 2017 13:55:12 -0500
Subject: [PATCH 04/12] Pep8

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

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 6e4a7721fc9a9..39793153aec3b 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -28,7 +28,7 @@
 from pandas.core.dtypes.cast import maybe_promote, maybe_upcast_putmask
 from pandas.core.dtypes.missing import isna, notna
 from pandas.core.dtypes.generic import ABCSeries, ABCPanel, ABCDataFrame
-from pandas.core.common import (_all_not_none, _count_not_none,
+from pandas.core.common import (_count_not_none,
                                 _maybe_box_datetimelike, _values_from_object,
                                 AbstractMethodError, SettingWithCopyError,
                                 SettingWithCopyWarning)

From 44e01da43668051b2b3cbda469c9c90f087c6be6 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Tue, 24 Oct 2017 14:25:41 -0500
Subject: [PATCH 05/12] Signature rewriting

---
 pandas/core/frame.py                  | 12 +++++++++++-
 pandas/tests/frame/test_alter_axes.py | 18 ++++++++++++++++-
 pandas/util/_decorators.py            | 28 ++++++++++++++++++++++++++-
 3 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 869880274a7c9..c773e41fa9497 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -82,7 +82,8 @@
 from pandas import compat
 from pandas.compat import PY36
 from pandas.compat.numpy import function as nv
-from pandas.util._decorators import Appender, Substitution
+from pandas.util._decorators import (Appender, Substitution,
+                                     rewrite_axis_style_signature)
 from pandas.util._validators import validate_bool_kwarg
 
 from pandas.core.indexes.period import PeriodIndex
@@ -2917,6 +2918,12 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
                                             broadcast_axis=broadcast_axis)
 
     @Appender(_shared_docs['reindex'] % _shared_doc_kwargs)
+    @rewrite_axis_style_signature('labels', [('method', None),
+                                             ('copy', True),
+                                             ('level', None),
+                                             ('fill_value', np.nan),
+                                             ('limit', None),
+                                             ('tolerance', None)])
     def reindex(self, *args, **kwargs):
         axes = self._validate_axis_style_args(args, kwargs, 'labels',
                                               'reindex')
@@ -2933,6 +2940,9 @@ def reindex_axis(self, labels, axis=0, method=None, level=None, copy=True,
                                         method=method, level=level, copy=copy,
                                         limit=limit, fill_value=fill_value)
 
+    @rewrite_axis_style_signature('mapper', [('copy', True),
+                                             ('inplace', False),
+                                             ('level', None)])
     def rename(self, *args, **kwargs):
         """Alter axes labels.
 
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index cf37890c423e1..0de32c733cd49 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -2,13 +2,14 @@
 
 from __future__ import print_function
 
+import inspect
 import pytest
 
 from datetime import datetime, timedelta
 
 import numpy as np
 
-from pandas.compat import lrange
+from pandas.compat import lrange, PY2
 from pandas import (DataFrame, Series, Index, MultiIndex,
                     RangeIndex, date_range, IntervalIndex,
                     to_datetime)
@@ -998,6 +999,21 @@ def test_ambiguous_warns(self):
         with tm.assert_produces_warning(UserWarning):
             df.rename({0: 10}, {"A": "B"})
 
+    @pytest.mark.skipif(PY2, reason="inspect.signature")
+    def test_rename_signature(self):
+        sig = inspect.signature(pd.DataFrame.rename)
+        parameters = set(sig.parameters)
+        assert parameters == {"self", "mapper", "index", "columns", "axis",
+                              "inplace", "copy", "level"}
+
+    @pytest.mark.skipif(PY2, reason="inspect.signature")
+    def test_reindex_signature(self):
+        sig = inspect.signature(pd.DataFrame.reindex)
+        parameters = set(sig.parameters)
+        assert parameters == {"self", "labels", "index", "columns", "axis",
+                              "limit", "copy", "level", "method",
+                              "fill_value", "tolerance"}
+
 
 class TestIntervalIndex(object):
 
diff --git a/pandas/util/_decorators.py b/pandas/util/_decorators.py
index 9e4e5515a292b..888d0493e2543 100644
--- a/pandas/util/_decorators.py
+++ b/pandas/util/_decorators.py
@@ -1,5 +1,6 @@
-from pandas.compat import callable, signature
+from pandas.compat import callable, signature, PY2
 from pandas._libs.properties import cache_readonly  # noqa
+import inspect
 import types
 import warnings
 from textwrap import dedent
@@ -122,6 +123,31 @@ def wrapper(*args, **kwargs):
 # Substitution and Appender are derived from matplotlib.docstring (1.1.0)
 # module http://matplotlib.org/users/license.html
 
+def rewrite_axis_style_signature(name, extra_params):
+    def decorate(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            return func(*args, **kwargs)
+
+        if not PY2:
+            kind = inspect.Parameter.POSITIONAL_OR_KEYWORD
+            params = [
+                inspect.Parameter('self', kind),
+                inspect.Parameter(name, kind, default=None),
+                inspect.Parameter('index', kind, default=None),
+                inspect.Parameter('columns', kind, default=None),
+                inspect.Parameter('axis', kind, default=None),
+            ]
+
+            for pname, default in extra_params:
+                params.append(inspect.Parameter(pname, kind, default=default))
+
+            sig = inspect.Signature(params)
+
+            func.__signature__ = sig
+        return wrapper
+    return decorate
+
 
 class Substitution(object):
     """

From 396a4540df4792891484281f72255944665c983f Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 06:46:47 -0500
Subject: [PATCH 06/12] Added docs, changed to futurewarning

---
 pandas/core/generic.py                        | 63 +++++++++++++++----
 pandas/tests/frame/test_alter_axes.py         |  6 +-
 .../tests/frame/test_axis_select_reindex.py   |  4 +-
 3 files changed, 57 insertions(+), 16 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 39793153aec3b..c7e49502d157d 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -2778,24 +2778,60 @@ def sort_index(self, axis=0, level=None, ascending=True, inplace=False,
         return self.reindex(**{axis_name: new_axis})
 
     def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
+        """Argument handler for mixed index, columns / axis functions
+
+        In an attempt to handle both `.method(index, columns)`, and
+        `.method(arg, axis=.)`, we have to do some bad things to argument
+        parsing. This translates all arguments to `{index=., columns=.}` style.
+
+        Parameters
+        ----------
+        arg : tuple
+            All positional arguments from the user
+        kwargs : dict
+            All keyword arguments from the user
+        arg_name, method_name : str
+            Used for better error messages
+
+        Returns
+        -------
+        kwargs : dict
+            A dictionary of keyword arguments. Doesn't modify ``kwargs``
+            inplace, so update them with the return value here.
+
+        Examples
+        --------
+        >>> df._validate_axis_style_args((str.upper,), {'columns': id},
+        ...                              'mapper', 'rename')
+        {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
+
+        This emits a warning
+        >>> df._validate_axis_style_args((str.upper, id), {},
+        ...                              'mapper', 'rename')
+        {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
+        """
+        # TODO(PY3): Change to keyword-only args and remove all this
+
         out = {}
-        # Goal: fill out with index/columns-style arguments
+        # Goal: fill 'out' with index/columns-style arguments
         # like out = {'index': foo, 'columns': bar}
-        # Start by validaing for consistency
+
+        # Start by validating for consistency
         if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
             msg = "Cannot specify both 'axis' and any of 'columns' or 'index'."
             raise TypeError(msg)
 
-        # Start with explicit values provided by the user...
+        # First fill with explicit values provided by the user...
         if arg_name in kwargs:
             if args:
-                msg = "{} got multiple values for argument '{}'".format(
-                    method_name, arg_name)
+                msg = ("{} got multiple values for argument "
+                       "'{}'".format(method_name, arg_name))
                 raise TypeError(msg)
+
             axis = self._get_axis_name(kwargs.get('axis', 0))
             out[axis] = kwargs[arg_name]
 
-        # fill in axes
+        # More user-provided arguments, now from kwargs
         for k, v in kwargs.items():
             try:
                 ax = self._get_axis_name(k)
@@ -2805,22 +2841,27 @@ def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
                 out[ax] = v
 
         # All user-provided kwargs have been handled now.
-        # Now we supplement with positional arguments, raising when there's
-        # ambiguity
+        # Now we supplement with positional arguments, emmitting warnings
+        # when there's ambiguity and raising when there's conflicts
 
         if len(args) == 0:
-            pass  # validate later
+            pass  # It's up to the function to decide if this is valid
         elif len(args) == 1:
             axis = self._get_axis_name(kwargs.get('axis', 0))
             out[axis] = args[0]
         elif len(args) == 2:
             if 'axis' in kwargs:
+                # Unambiguously wrong
                 msg = "Cannot specify both {} and any of 'index' or 'columns'"
                 raise TypeError(msg.format(arg_name))
+
             msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
                    "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
-                   "arguments to remove any ambiguity.")
-            warnings.warn(msg.format(method_name=method_name,), stacklevel=3)
+                   "arguments to remove any ambiguity. In the future, using "
+                   "positional arguments for 'index' or 'columns' will raise "
+                   " a 'TypeError'.")
+            warnings.warn(msg.format(method_name=method_name,), FutureWarning,
+                          stacklevel=4)
             out[self._AXIS_NAMES[0]] = args[0]
             out[self._AXIS_NAMES[1]] = args[1]
         else:
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 0de32c733cd49..8140b7bb04b59 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -959,7 +959,7 @@ def test_reindex_api_equivalence(self):
 
     def test_rename_positional(self):
         df = pd.DataFrame(columns=['A', 'B'])
-        with tm.assert_produces_warning(UserWarning) as rec:
+        with tm.assert_produces_warning(FutureWarning) as rec:
             result = df.rename(None, str.lower)
         expected = pd.DataFrame(columns=['a', 'b'])
         assert_frame_equal(result, expected)
@@ -993,10 +993,10 @@ def test_set_index_preserve_categorical_dtype(self):
 
     def test_ambiguous_warns(self):
         df = pd.DataFrame({"A": [1, 2]})
-        with tm.assert_produces_warning(UserWarning):
+        with tm.assert_produces_warning(FutureWarning):
             df.rename(id, id)
 
-        with tm.assert_produces_warning(UserWarning):
+        with tm.assert_produces_warning(FutureWarning):
             df.rename({0: 10}, {"A": "B"})
 
     @pytest.mark.skipif(PY2, reason="inspect.signature")
diff --git a/pandas/tests/frame/test_axis_select_reindex.py b/pandas/tests/frame/test_axis_select_reindex.py
index ebfc8fb3f21e3..a3dbb643d32fd 100644
--- a/pandas/tests/frame/test_axis_select_reindex.py
+++ b/pandas/tests/frame/test_axis_select_reindex.py
@@ -468,7 +468,7 @@ def test_reindex_positional_warns(self):
         df = pd.DataFrame({"A": [1, 2, 3], "B": [4, 5, 6]})
         expected = pd.DataFrame({"A": [1., 2], 'B': [4., 5],
                                  "C": [np.nan, np.nan]})
-        with tm.assert_produces_warning(UserWarning):
+        with tm.assert_produces_warning(FutureWarning):
             result = df.reindex([0, 1], ['A', 'B', 'C'])
 
         assert_frame_equal(result, expected)
@@ -532,7 +532,7 @@ def test_reindex_api_equivalence(self):
         for res in [res2, res3]:
             tm.assert_frame_equal(res1, res)
 
-        with tm.assert_produces_warning(UserWarning) as m:
+        with tm.assert_produces_warning(FutureWarning) as m:
             res1 = df.reindex(['b', 'a'], ['e', 'd'])
         assert 'reindex' in str(m[0].message)
         res2 = df.reindex(columns=['e', 'd'], index=['b', 'a'])

From 3cb3fac094a3be5780df8f8051f169df139d7cd6 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 06:58:00 -0500
Subject: [PATCH 07/12] Move comment

---
 pandas/util/_decorators.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/util/_decorators.py b/pandas/util/_decorators.py
index 888d0493e2543..7c9250e52d482 100644
--- a/pandas/util/_decorators.py
+++ b/pandas/util/_decorators.py
@@ -120,9 +120,6 @@ def wrapper(*args, **kwargs):
     return _deprecate_kwarg
 
 
-# Substitution and Appender are derived from matplotlib.docstring (1.1.0)
-# module http://matplotlib.org/users/license.html
-
 def rewrite_axis_style_signature(name, extra_params):
     def decorate(func):
         @wraps(func)
@@ -148,6 +145,9 @@ def wrapper(*args, **kwargs):
         return wrapper
     return decorate
 
+# Substitution and Appender are derived from matplotlib.docstring (1.1.0)
+# module http://matplotlib.org/users/license.html
+
 
 class Substitution(object):
     """

From 4766c242550c42d7886684401a8b8febf0fed300 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 17:08:35 -0500
Subject: [PATCH 08/12] Catch bug in rename

---
 pandas/core/frame.py                  | 3 +++
 pandas/tests/frame/test_alter_axes.py | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index c773e41fa9497..47a68de88daee 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -2928,6 +2928,7 @@ def reindex(self, *args, **kwargs):
         axes = self._validate_axis_style_args(args, kwargs, 'labels',
                                               'reindex')
         kwargs.update(axes)
+        # Pop these, since the values are in `kwargs` under different names
         kwargs.pop('axis', None)
         kwargs.pop('labels', None)
         return super(DataFrame, self).reindex(**kwargs)
@@ -3019,7 +3020,9 @@ def rename(self, *args, **kwargs):
         """
         axes = self._validate_axis_style_args(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(DataFrame, self).rename(**kwargs)
 
     @Appender(_shared_docs['fillna'] % _shared_doc_kwargs)
diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index 8140b7bb04b59..a4745f6522a85 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -888,6 +888,9 @@ def test_rename_axis_style(self):
         result = df.rename({'X': 'x', 'Y': 'y'}, axis='index')
         assert_frame_equal(result, expected)
 
+        result = df.rename(mapper=str.lower, axis='index')
+        assert_frame_equal(result, expected)
+
     def test_rename_mapper_multi(self):
         df = pd.DataFrame({"A": ['a', 'b'], "B": ['c', 'd'],
                            'C': [1, 2]}).set_index(["A", "B"])

From ccbd75edf3d477c8374f1550f47621a9440191cc Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 17:12:43 -0500
Subject: [PATCH 09/12] Fill in coverage

---
 pandas/tests/frame/test_alter_axes.py          | 4 ++++
 pandas/tests/frame/test_axis_select_reindex.py | 4 ++++
 pandas/tests/test_panel.py                     | 9 +++++++++
 3 files changed, 17 insertions(+)

diff --git a/pandas/tests/frame/test_alter_axes.py b/pandas/tests/frame/test_alter_axes.py
index a4745f6522a85..e7ea3f9c62540 100644
--- a/pandas/tests/frame/test_alter_axes.py
+++ b/pandas/tests/frame/test_alter_axes.py
@@ -933,6 +933,10 @@ def test_rename_axis_style_raises(self):
         with tm.assert_raises_regex(TypeError, None):
             df.rename(str.lower, str.lower, str.lower)
 
+        # Duplicates
+        with tm.assert_raises_regex(TypeError, "multiple values"):
+            df.rename(id, mapper=id)
+
     def test_reindex_api_equivalence(self):
         # equivalence of the labels/axis and index/columns API's
         df = DataFrame([[1, 2, 3], [3, 4, 5], [5, 6, 7]],
diff --git a/pandas/tests/frame/test_axis_select_reindex.py b/pandas/tests/frame/test_axis_select_reindex.py
index a3dbb643d32fd..1e161adb80331 100644
--- a/pandas/tests/frame/test_axis_select_reindex.py
+++ b/pandas/tests/frame/test_axis_select_reindex.py
@@ -504,6 +504,10 @@ def test_reindex_axis_style_raises(self):
         with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex(index=[0, 1], axis='columns')
 
+        # Duplicates
+        with tm.assert_raises_regex(TypeError, "multiple values"):
+            df.reindex([0, 1], labels=[0, 1])
+
     def test_reindex_single_named_indexer(self):
         # https://github.com/pandas-dev/pandas/issues/12392
         df = pd.DataFrame({"A": [1, 2, 3], "B": [1, 2, 3]})
diff --git a/pandas/tests/test_panel.py b/pandas/tests/test_panel.py
index e845fcac33323..faee6ff0a5747 100644
--- a/pandas/tests/test_panel.py
+++ b/pandas/tests/test_panel.py
@@ -1424,6 +1424,11 @@ def test_reindex(self):
             result = self.panel.reindex(minor=new_minor)
             assert_frame_equal(result['ItemB'], ref.reindex(columns=new_minor))
 
+            # raise exception put both major and major_axis
+            pytest.raises(Exception, self.panel.reindex,
+                          minor_axis=new_minor,
+                          minor=new_minor)
+
             # this ok
             result = self.panel.reindex()
             assert_panel_equal(result, self.panel)
@@ -1460,6 +1465,10 @@ def test_reindex_axis_style(self):
             result = panel.reindex([0, 1], axis=2)
             assert_panel_equal(result, expected2)
 
+            result = panel.reindex([0, 1], axis=2)
+            assert_panel_equal(result, expected2)
+
+
     def test_reindex_multi(self):
         with catch_warnings(record=True):
 

From d01aa20d60c655f5803c00956580417a95961ea4 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 20:52:14 -0500
Subject: [PATCH 10/12] pep8

---
 pandas/tests/test_panel.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/tests/test_panel.py b/pandas/tests/test_panel.py
index faee6ff0a5747..33fb6f1108bf2 100644
--- a/pandas/tests/test_panel.py
+++ b/pandas/tests/test_panel.py
@@ -1468,7 +1468,6 @@ def test_reindex_axis_style(self):
             result = panel.reindex([0, 1], axis=2)
             assert_panel_equal(result, expected2)
 
-
     def test_reindex_multi(self):
         with catch_warnings(record=True):
 

From 1c1517ac968b0aeab71a553f2a8540a6e4552581 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Wed, 25 Oct 2017 20:58:22 -0500
Subject: [PATCH 11/12] Fixed error message

---
 pandas/core/generic.py                         | 7 ++++---
 pandas/tests/frame/test_axis_select_reindex.py | 4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index c7e49502d157d..350705aca1705 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -2818,7 +2818,7 @@ def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
 
         # Start by validating for consistency
         if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
-            msg = "Cannot specify both 'axis' and any of 'columns' or 'index'."
+            msg = "Cannot specify both 'axis' and any of 'index' or 'columns'."
             raise TypeError(msg)
 
         # First fill with explicit values provided by the user...
@@ -2852,8 +2852,9 @@ def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
         elif len(args) == 2:
             if 'axis' in kwargs:
                 # Unambiguously wrong
-                msg = "Cannot specify both {} and any of 'index' or 'columns'"
-                raise TypeError(msg.format(arg_name))
+                msg = ("Cannot specify both 'axis' and any of 'index' "
+                       "or 'columns'")
+                raise TypeError(msg)
 
             msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
                    "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
diff --git a/pandas/tests/frame/test_axis_select_reindex.py b/pandas/tests/frame/test_axis_select_reindex.py
index 1e161adb80331..1e2f630401c89 100644
--- a/pandas/tests/frame/test_axis_select_reindex.py
+++ b/pandas/tests/frame/test_axis_select_reindex.py
@@ -476,10 +476,10 @@ def test_reindex_positional_warns(self):
     def test_reindex_axis_style_raises(self):
         # https://github.com/pandas-dev/pandas/issues/12392
         df = pd.DataFrame({"A": [1, 2, 3], 'B': [4, 5, 6]})
-        with tm.assert_raises_regex(TypeError, 'Cannot specify both labels'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex([0, 1], ['A'], axis=1)
 
-        with tm.assert_raises_regex(TypeError, 'Cannot specify both labels'):
+        with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):
             df.reindex([0, 1], ['A'], axis='index')
 
         with tm.assert_raises_regex(TypeError, "Cannot specify both 'axis'"):

From edcbb9ac526ae2ec7c56915d02ba6a083d830a81 Mon Sep 17 00:00:00 2001
From: Tom Augspurger <tom.w.augspurger@gmail.com>
Date: Thu, 26 Oct 2017 20:28:49 -0500
Subject: [PATCH 12/12] Move to validators

---
 pandas/core/frame.py       |  9 ++--
 pandas/core/generic.py     | 93 ------------------------------------
 pandas/core/panel.py       |  9 ++--
 pandas/core/panel4d.py     |  4 +-
 pandas/util/_validators.py | 96 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 107 insertions(+), 104 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 47a68de88daee..a1af806e5cb9e 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -84,7 +84,8 @@
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import (Appender, Substitution,
                                      rewrite_axis_style_signature)
-from pandas.util._validators import validate_bool_kwarg
+from pandas.util._validators import (validate_bool_kwarg,
+                                     validate_axis_style_args)
 
 from pandas.core.indexes.period import PeriodIndex
 from pandas.core.indexes.datetimes import DatetimeIndex
@@ -2925,8 +2926,8 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
                                              ('limit', None),
                                              ('tolerance', None)])
     def reindex(self, *args, **kwargs):
-        axes = self._validate_axis_style_args(args, kwargs, 'labels',
-                                              'reindex')
+        axes = validate_axis_style_args(self, args, kwargs, 'labels',
+                                        'reindex')
         kwargs.update(axes)
         # Pop these, since the values are in `kwargs` under different names
         kwargs.pop('axis', None)
@@ -3018,7 +3019,7 @@ def rename(self, *args, **kwargs):
         2  2  5
         4  3  6
         """
-        axes = self._validate_axis_style_args(args, kwargs, 'mapper', 'rename')
+        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)
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 350705aca1705..118e7d5cd437b 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -2777,99 +2777,6 @@ def sort_index(self, axis=0, level=None, ascending=True, inplace=False,
         new_axis = labels.take(sort_index)
         return self.reindex(**{axis_name: new_axis})
 
-    def _validate_axis_style_args(self, args, kwargs, arg_name, method_name):
-        """Argument handler for mixed index, columns / axis functions
-
-        In an attempt to handle both `.method(index, columns)`, and
-        `.method(arg, axis=.)`, we have to do some bad things to argument
-        parsing. This translates all arguments to `{index=., columns=.}` style.
-
-        Parameters
-        ----------
-        arg : tuple
-            All positional arguments from the user
-        kwargs : dict
-            All keyword arguments from the user
-        arg_name, method_name : str
-            Used for better error messages
-
-        Returns
-        -------
-        kwargs : dict
-            A dictionary of keyword arguments. Doesn't modify ``kwargs``
-            inplace, so update them with the return value here.
-
-        Examples
-        --------
-        >>> df._validate_axis_style_args((str.upper,), {'columns': id},
-        ...                              'mapper', 'rename')
-        {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
-
-        This emits a warning
-        >>> df._validate_axis_style_args((str.upper, id), {},
-        ...                              'mapper', 'rename')
-        {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
-        """
-        # TODO(PY3): Change to keyword-only args and remove all this
-
-        out = {}
-        # Goal: fill 'out' with index/columns-style arguments
-        # like out = {'index': foo, 'columns': bar}
-
-        # Start by validating for consistency
-        if 'axis' in kwargs and any(x in kwargs for x in self._AXIS_NUMBERS):
-            msg = "Cannot specify both 'axis' and any of 'index' or 'columns'."
-            raise TypeError(msg)
-
-        # First fill with explicit values provided by the user...
-        if arg_name in kwargs:
-            if args:
-                msg = ("{} got multiple values for argument "
-                       "'{}'".format(method_name, arg_name))
-                raise TypeError(msg)
-
-            axis = self._get_axis_name(kwargs.get('axis', 0))
-            out[axis] = kwargs[arg_name]
-
-        # More user-provided arguments, now from kwargs
-        for k, v in kwargs.items():
-            try:
-                ax = self._get_axis_name(k)
-            except ValueError:
-                pass
-            else:
-                out[ax] = v
-
-        # All user-provided kwargs have been handled now.
-        # Now we supplement with positional arguments, emmitting warnings
-        # when there's ambiguity and raising when there's conflicts
-
-        if len(args) == 0:
-            pass  # It's up to the function to decide if this is valid
-        elif len(args) == 1:
-            axis = self._get_axis_name(kwargs.get('axis', 0))
-            out[axis] = args[0]
-        elif len(args) == 2:
-            if 'axis' in kwargs:
-                # Unambiguously wrong
-                msg = ("Cannot specify both 'axis' and any of 'index' "
-                       "or 'columns'")
-                raise TypeError(msg)
-
-            msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
-                   "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
-                   "arguments to remove any ambiguity. In the future, using "
-                   "positional arguments for 'index' or 'columns' will raise "
-                   " a 'TypeError'.")
-            warnings.warn(msg.format(method_name=method_name,), FutureWarning,
-                          stacklevel=4)
-            out[self._AXIS_NAMES[0]] = args[0]
-            out[self._AXIS_NAMES[1]] = args[1]
-        else:
-            msg = "Cannot specify all of '{}', 'index', 'columns'."
-            raise TypeError(msg.format(arg_name))
-        return out
-
     _shared_docs['reindex'] = """
         Conform %(klass)s to new index with optional filling logic, placing
         NA/NaN in locations having no value in the previous index. A new object
diff --git a/pandas/core/panel.py b/pandas/core/panel.py
index 77e706d9dcf49..d2b513367fc78 100644
--- a/pandas/core/panel.py
+++ b/pandas/core/panel.py
@@ -35,6 +35,7 @@
 from pandas.core.series import Series
 from pandas.core.reshape.util import cartesian_product
 from pandas.util._decorators import (deprecate, Appender)
+from pandas.util._validators import validate_axis_style_args
 
 _shared_doc_kwargs = dict(
     axes='items, major_axis, minor_axis',
@@ -1212,12 +1213,8 @@ def reindex(self, *args, **kwargs):
                 raise TypeError("Cannot specify both 'minor' and 'minor_axis'")
 
             kwargs['minor_axis'] = minor
-        # major_axis = (major_axis if major_axis is not None else
-        #               kwargs.pop('major', None))
-        # minor_axis = (minor_axis if minor_axis is not None else
-        #               kwargs.pop('minor', None))
-        axes = self._validate_axis_style_args(args, kwargs, 'labels',
-                                              'reindex')
+        axes = validate_axis_style_args(self, args, kwargs, 'labels',
+                                        'reindex')
         if self.ndim >= 4:
             # Hack for PanelND
             axes = {}
diff --git a/pandas/core/panel4d.py b/pandas/core/panel4d.py
index ba5853117b38e..0fac720302cfb 100644
--- a/pandas/core/panel4d.py
+++ b/pandas/core/panel4d.py
@@ -4,6 +4,8 @@
 from pandas.core.generic import NDFrame
 from pandas.core.panelnd import create_nd_panel_factory
 from pandas.core.panel import Panel
+from pandas.util._validators import validate_axis_style_args
+
 
 Panel4D = create_nd_panel_factory(klass_name='Panel4D',
                                   orders=['labels', 'items', 'major_axis',
@@ -88,7 +90,7 @@ def panel4d_reindex(self, labs=None, labels=None, items=None, major_axis=None,
     if axis is not None:
         kwargs_['axis'] = axis
 
-    axes = self._validate_axis_style_args(args, kwargs_, 'labs', 'reindex')
+    axes = validate_axis_style_args(self, args, kwargs_, 'labs', 'reindex')
     kwargs.update(axes)
     return NDFrame.reindex(self, **kwargs)
 
diff --git a/pandas/util/_validators.py b/pandas/util/_validators.py
index 2661e4a98aedf..728db6af5558b 100644
--- a/pandas/util/_validators.py
+++ b/pandas/util/_validators.py
@@ -2,6 +2,7 @@
 Module that contains many useful utilities
 for validating data or function arguments
 """
+import warnings
 
 from pandas.core.dtypes.common import is_bool
 
@@ -224,3 +225,98 @@ def validate_bool_kwarg(value, arg_name):
                          'type {typ}.'.format(arg=arg_name,
                                               typ=type(value).__name__))
     return value
+
+
+def validate_axis_style_args(data, args, kwargs, arg_name, method_name):
+    """Argument handler for mixed index, columns / axis functions
+
+    In an attempt to handle both `.method(index, columns)`, and
+    `.method(arg, axis=.)`, we have to do some bad things to argument
+    parsing. This translates all arguments to `{index=., columns=.}` style.
+
+    Parameters
+    ----------
+    data : DataFrame or Panel
+    arg : tuple
+        All positional arguments from the user
+    kwargs : dict
+        All keyword arguments from the user
+    arg_name, method_name : str
+        Used for better error messages
+
+    Returns
+    -------
+    kwargs : dict
+        A dictionary of keyword arguments. Doesn't modify ``kwargs``
+        inplace, so update them with the return value here.
+
+    Examples
+    --------
+    >>> df._validate_axis_style_args((str.upper,), {'columns': id},
+    ...                              'mapper', 'rename')
+    {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
+
+    This emits a warning
+    >>> df._validate_axis_style_args((str.upper, id), {},
+    ...                              'mapper', 'rename')
+    {'columns': <function id>, 'index': <method 'upper' of 'str' objects>}
+    """
+    # TODO(PY3): Change to keyword-only args and remove all this
+
+    out = {}
+    # Goal: fill 'out' with index/columns-style arguments
+    # like out = {'index': foo, 'columns': bar}
+
+    # Start by validating for consistency
+    if 'axis' in kwargs and any(x in kwargs for x in data._AXIS_NUMBERS):
+        msg = "Cannot specify both 'axis' and any of 'index' or 'columns'."
+        raise TypeError(msg)
+
+    # First fill with explicit values provided by the user...
+    if arg_name in kwargs:
+        if args:
+            msg = ("{} got multiple values for argument "
+                   "'{}'".format(method_name, arg_name))
+            raise TypeError(msg)
+
+        axis = data._get_axis_name(kwargs.get('axis', 0))
+        out[axis] = kwargs[arg_name]
+
+    # More user-provided arguments, now from kwargs
+    for k, v in kwargs.items():
+        try:
+            ax = data._get_axis_name(k)
+        except ValueError:
+            pass
+        else:
+            out[ax] = v
+
+    # All user-provided kwargs have been handled now.
+    # Now we supplement with positional arguments, emmitting warnings
+    # when there's ambiguity and raising when there's conflicts
+
+    if len(args) == 0:
+        pass  # It's up to the function to decide if this is valid
+    elif len(args) == 1:
+        axis = data._get_axis_name(kwargs.get('axis', 0))
+        out[axis] = args[0]
+    elif len(args) == 2:
+        if 'axis' in kwargs:
+            # Unambiguously wrong
+            msg = ("Cannot specify both 'axis' and any of 'index' "
+                   "or 'columns'")
+            raise TypeError(msg)
+
+        msg = ("Intepreting call\n\t'.{method_name}(a, b)' as "
+               "\n\t'.{method_name}(index=a, columns=b)'.\nUse named "
+               "arguments to remove any ambiguity. In the future, using "
+               "positional arguments for 'index' or 'columns' will raise "
+               " a 'TypeError'.")
+        warnings.warn(msg.format(method_name=method_name,), FutureWarning,
+                      stacklevel=4)
+        out[data._AXIS_NAMES[0]] = args[0]
+        out[data._AXIS_NAMES[1]] = args[1]
+    else:
+        msg = "Cannot specify all of '{}', 'index', 'columns'."
+        raise TypeError(msg.format(arg_name))
+    return out