MAINT: Drop Index.sym_diff

Deprecated in 0.18.1

xref gh-12591, gh-12594

Author: gfyoung

doc/source/whatsnew/v0.21.0.txt

@@ -75,6 +75,7 @@ Removal of prior version deprecations/changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 - :func:`read_excel()` has dropped the ``has_index_names`` parameter (:issue:`10967`)
+- ``Index`` has dropped the ``.sym_diff()`` method in favor of ``.symmetric_difference()`` (:issue:`12591`)
 - ``Categorical`` has dropped the ``.order()`` and ``.sort()`` methods in favor of ``.sort_values()`` (:issue:`12882`)
 
 

pandas/core/indexes/base.py

@@ -2376,8 +2376,6 @@ def symmetric_difference(self, other, result_name=None):
             attribs['freq'] = None
         return self._shallow_copy_with_infer(the_diff, **attribs)
 
-    sym_diff = deprecate('sym_diff', symmetric_difference)
-
     def _get_unique_index(self, dropna=False):
         """
         Returns an index containing unique values.

pandas/tests/indexes/common.py

@@ -656,11 +656,7 @@ def test_symmetric_difference(self):
             if isinstance(idx, MultiIndex):
                 msg = "other must be a MultiIndex or a list of tuples"
                 with tm.assert_raises_regex(TypeError, msg):
-                    result = first.symmetric_difference([1, 2, 3])
-
-        # 12591 deprecated
-        with tm.assert_produces_warning(FutureWarning):
-            first.sym_diff(second)
+                    first.symmetric_difference([1, 2, 3])
 
     def test_insert_base(self):