COMPAT: Remove use of private re attribute

Closes pandas-dev#20551

Author: TomAugspurger

pandas/compat/__init__.py

@@ -423,6 +423,12 @@ def raise_with_traceback(exc, traceback=Ellipsis):
 parse_date = _date_parser.parse
 
 
+if PY36:
+    import typing
+    re_type = typing.re.Pattern
+else:
+    re_type = type(re.compile(''))
+
 # https://github.com/pandas-dev/pandas/pull/9123
 def is_platform_little_endian():
     """ am I little endian """

pandas/core/dtypes/inference.py

@@ -6,7 +6,7 @@
 from collections import Iterable
 from numbers import Number
 from pandas.compat import (PY2, string_types, text_type,
-                           string_and_binary_types)
+                           string_and_binary_types, re_type)
 from pandas._libs import lib
 
 is_bool = lib.is_bool
@@ -216,7 +216,7 @@ def is_re(obj):
     False
     """
 
-    return isinstance(obj, re._pattern_type)
+    return isinstance(obj, re_type)
 
 
 def is_re_compilable(obj):