Closes #26809: Merge with 3.5

Lib/string.py

@@ -14,6 +14,10 @@ printable -- a string containing all ASCII characters considered printable
 
 """
 
+__all__ = ["ascii_letters", "ascii_lowercase", "ascii_uppercase", "capwords",
+           "digits", "hexdigits", "octdigits", "printable", "punctuation",
+           "whitespace", "Formatter", "Template"]
+
 import _string
 
 # Some strings for ctype-style character classification
@@ -46,7 +50,7 @@ def capwords(s, sep=None):
 
 ####################################################################
 import re as _re
-from collections import ChainMap
+from collections import ChainMap as _ChainMap
 
 class _TemplateMetaclass(type):
     pattern = r"""
@@ -104,7 +108,7 @@ class Template(metaclass=_TemplateMetaclass):
         if not args:
             mapping = kws
         elif kws:
-            mapping = ChainMap(kws, args[0])
+            mapping = _ChainMap(kws, args[0])
         else:
             mapping = args[0]
         # Helper function for .sub()
@@ -131,7 +135,7 @@ class Template(metaclass=_TemplateMetaclass):
         if not args:
             mapping = kws
         elif kws:
-            mapping = ChainMap(kws, args[0])
+            mapping = _ChainMap(kws, args[0])
         else:
             mapping = args[0]
         # Helper function for .sub()

Misc/NEWS

@@ -27,6 +27,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #26809: Add ``__all__`` to :mod:`string`.  Patch by Emanuel Barry.
+
 - Issue #26373: subprocess.Popen.communicate now correctly ignores
   BrokenPipeError when the child process dies before .communicate()
   is called in more/all circumstances.