Review (jreback)

Author: h-vetinari

pandas/core/frame.py

@@ -6537,7 +6537,7 @@ def _join_compat(self, other, on=None, how='left', lsuffix='', rsuffix='',
             if can_concat:
                 if how == 'left':
                     res = concat(frames, axis=1, join='outer',
-                                 verify_integrity=True, copy=False)
+                                 verify_integrity=True)
                     res = res.reindex(self.index, copy=False)
                     return res
                 else:

pandas/core/generic.py

@@ -8930,8 +8930,8 @@ def describe_1d(data):
                 if name not in names:
                     names.append(name)
 
-        d = pd.concat([x.reindex(names) for x in ldesc], axis=1,
-                      sort=False, copy=False)
+        d = pd.concat([x.reindex(names, copy=False) for x in ldesc],
+                      axis=1, sort=False)
         d.columns = data.columns.copy()
         return d
 

pandas/core/groupby/generic.py

@@ -519,8 +519,7 @@ def _transform_general(self, func, *args, **kwargs):
 
         concat_index = obj.columns if self.axis == 0 else obj.index
         other_axis = 1 if self.axis == 0 else 0  # switches between 0 & 1
-        concatenated = concat(applied, axis=self.axis,
-                              verify_integrity=False, copy=False)
+        concatenated = concat(applied, axis=self.axis, verify_integrity=False)
         concatenated = concatenated.reindex(concat_index, axis=other_axis,
                                             copy=False)
         return self._set_result_index_ordered(concatenated)

pandas/core/reshape/concat.py

@@ -227,6 +227,7 @@ def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
     res = op.get_result()
 
     if join_axes is not None:
+        # GH 21951
         warnings.warn('The join_axes-keyword is deprecated. Use .reindex or '
                       '.reindex_like on the result to achieve the same '
                       'functionality.', FutureWarning, stacklevel=2)
@@ -236,12 +237,12 @@ def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
                                  "length {length}".format(length=ndim - 1))
         if ndim == 2:
             other_axis = 1 if axis == 0 else 0  # switches between 0 & 1
-            res = res.reindex(join_axes[0], axis=other_axis)
+            res = res.reindex(join_axes[0], axis=other_axis, copy=False)
         elif ndim == 3:  # Panel
             other_axes = list(range(res.ndim))
             other_axes.pop(axis)
             for i in range(ndim - 1):
-                res.reindex(join_axes[i], axis=i)
+                res.reindex(join_axes[i], axis=i, copy=False)
     return res