Add file_types to allow checking if variable isinstance of file

documentation/index.rst

@@ -78,6 +78,12 @@ Six provides constants that may differ between Python versions.  Ones ending
    :func:`py3:bytes` in Python 3.
 
 
+.. data:: file_types
+
+   Possible types for files.  This is :func:`py2:file` and :func:`py2:io.IOBase`
+   in Python 2 and just :func:`py3:io.IOBase` in Python 3.
+
+
 .. data:: MAXSIZE
 
    The maximum  size of a  container like :func:`py3:list`  or :func:`py3:dict`.

six.py

@@ -23,6 +23,7 @@
 from __future__ import absolute_import
 
 import functools
+import io
 import itertools
 import operator
 import sys
@@ -43,6 +44,7 @@
     class_types = type,
     text_type = str
     binary_type = bytes
+    file_types = (io.IOBase, )
 
     MAXSIZE = sys.maxsize
 else:
@@ -51,6 +53,7 @@
     class_types = (type, types.ClassType)
     text_type = unicode
     binary_type = str
+    file_types = (file, io.IOBase)
 
     if sys.platform.startswith("java"):
         # Jython always uses 32 bits.
@@ -634,7 +637,6 @@ def u(s):
     byte2int = operator.itemgetter(0)
     indexbytes = operator.getitem
     iterbytes = iter
-    import io
     StringIO = io.StringIO
     BytesIO = io.BytesIO
     _assertCountEqual = "assertCountEqual"

test_six.py

@@ -73,6 +73,12 @@ def test_binary_type():
     assert type(six.b("hi")) is six.binary_type
 
 
+def test_file_types():
+    import tempfile
+    with tempfile.TemporaryFile() as fh:
+        assert isinstance(fh, six.file_types)
+
+
 def test_MAXSIZE():
     try:
         # This shouldn't raise an overflow error.