move union_categoricals to pandas.api.types

Author: jreback

doc/source/categorical.rst

@@ -673,7 +673,7 @@ will be the union of the categories being combined.
 
 .. ipython:: python
 
-    from pandas.types.concat import union_categoricals
+    from pandas.api.types import union_categoricals
     a = pd.Categorical(["b", "c"])
     b = pd.Categorical(["a", "b"])
     union_categoricals([a, b])

doc/source/whatsnew/v0.20.0.txt

@@ -488,7 +488,7 @@ Other Enhancements
 - HTML table output skips ``colspan`` or ``rowspan`` attribute if equal to 1. (:issue:`15403`)
 
 - ``TimedeltaIndex`` now has a custom datetick formatter specifically designed for nanosecond level precision (:issue:`8711`)
-- ``pd.types.concat.union_categoricals`` gained the ``ignore_ordered`` argument to allow ignoring the ordered attribute of unioned categoricals (:issue:`13410`). See the :ref:`categorical union docs <categorical.union>` for more information.
+- ``pd.api.types.union_categoricals`` gained the ``ignore_ordered`` argument to allow ignoring the ordered attribute of unioned categoricals (:issue:`13410`). See the :ref:`categorical union docs <categorical.union>` for more information.
 - ``DataFrame.to_latex()`` and ``DataFrame.to_string()`` now allow optional header aliases. (:issue:`15536`)
 - Re-enable the ``parse_dates`` keyword of ``pd.read_excel()`` to parse string columns as dates (:issue:`14326`)
 - Added ``.empty`` property to subclasses of ``Index``. (:issue:`15270`)
@@ -1031,6 +1031,8 @@ If indicated, a deprecation warning will be issued if you reference that module.
     "pandas._hash", "pandas.tools.libhash", ""
     "pandas._window", "pandas.core.libwindow", ""
 
+- The function :func:`~pandas.api.type.union_categoricals` is now importable from ``pandas.api.types``, formerly from ``pandas.types.concat`` (:issue:`15998`)
+
 .. _whatsnew_0200.api_breaking.sort_index:
 
 DataFrame.sort_index changes

pandas/api/types/__init__.py

@@ -1,4 +1,5 @@
 """ public toolkit API """
 
 from pandas.core.typed.api import *  # noqa
+from pandas.core.typed.concat import union_categoricals  # noqa
 del np  # noqa

pandas/core/algorithms.py

@@ -28,7 +28,7 @@
 from pandas.compat.numpy import _np_version_under1p10
 from pandas.core.typed.missing import isnull
 
-import pandas.core.common as com
+from pandas.core import common as com
 from pandas.compat import string_types
 from pandas._libs import algos, lib, hashtable as htable
 from pandas._libs.tslib import iNaT

pandas/tests/api/test_types.py

@@ -30,7 +30,7 @@ class TestTypes(Base, tm.TestCase):
                'is_dict_like', 'is_iterator', 'is_file_like',
                'is_list_like', 'is_hashable',
                'is_named_tuple', 'is_sequence',
-               'pandas_dtype']
+               'pandas_dtype', 'union_categoricals']
 
     def test_types(self):