Cleanup messages, generic

Author: TomAugspurger

pandas/core/frame.py

@@ -113,7 +113,7 @@
         by : str or list of str
             Name or list of names which refer to the axis items.""",
     versionadded_to_excel='',
-    mapper = """mapper : dict-like or function
+    mapper="""mapper : dict-like or function
             Applied to the axis specified by `axis`""",
 )
 
@@ -2911,11 +2911,12 @@ def reindex_axis(self, labels, axis=0, method=None, level=None, copy=True,
     def rename(self, mapper=None, index=None, columns=None, axis=None,
                **kwargs):
         if axis is not None:
+            # Using "axis" style, along with a positional mapper
+            # Both index and columns should be None then
             axis = self._get_axis_name(axis)
-            # interpreting 'mapper' as a positional argument
             if index is not None or columns is not None:
-                raise TypeError("Can't specify 'index' or 'columns' and 'axis'"
-                                " at the same time. Specify either\n"
+                raise TypeError("Can't specify both 'axis' and 'index' or "
+                                "'columns' Specify either\n"
                                 "\t.rename(mapper, axis=axis), or\n"
                                 "\t.rename(index=index, columns=columns)")
             if axis == 'index':
@@ -2929,8 +2930,10 @@ def rename(self, mapper=None, index=None, columns=None, axis=None,
         elif axis is None and (mapper is not None and index is not None):
             # Determine if they meant df.rename(idx_map, col_map)
             if callable(index) or is_dict_like(index):
-                warnings.warn("Interpreting renaming index and columns. "
-                              "Use keyword arguments.", UserWarning)
+                warnings.warn("Interpreting call to '.rename(a, b)' as "
+                              "'.rename(index=a, columns=b)'. "
+                              "Use keyword arguments to remove ambiguity.",
+                              UserWarning)
                 index, columns = mapper, index
         elif index is None and columns is None:
             index = mapper

pandas/core/generic.py

@@ -828,16 +828,6 @@ def rename(self, *args, **kwargs):
         copy = kwargs.pop('copy', True)
         inplace = kwargs.pop('inplace', False)
         level = kwargs.pop('level', None)
-        axis = kwargs.pop("axis", None)
-
-        if axis:
-            # At this point, we know the call was
-            # rename(fn, axis=axis), so axes is always
-            # {index: op, columns: None}
-            axis = self._get_axis_name(axis)
-            op = axes['index']
-            axes['index'] = None
-            axes[axis] = op
 
         if kwargs:
             raise TypeError('rename() got an unexpected keyword '