COMPAT: Remove use of private re attribute (#20553)

Author: TomAugspurger

pandas/compat/__init__.py

@@ -26,6 +26,7 @@
 # pylint disable=W0611
 # flake8: noqa
 
+import re
 import functools
 import itertools
 from distutils.version import LooseVersion
@@ -136,7 +137,6 @@ def lfilter(*args, **kwargs):
 
 else:
     # Python 2
-    import re
     _name_re = re.compile(r"[a-zA-Z_][a-zA-Z0-9_]*$")
 
     FileNotFoundError = IOError
@@ -423,6 +423,14 @@ def raise_with_traceback(exc, traceback=Ellipsis):
 parse_date = _date_parser.parse
 
 
+# In Python 3.7, the private re._pattern_type is removed.
+# Python 3.5+ have typing.re.Pattern
+if PY35:
+    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):