Refinement changes:

* Use assertListEqual to ensure alternate month names the same as regular
for the "C" locale.
* Use `_supports_alternative_month_names` as more descriptive name.
* Add `versionadded:: next` tags to the new APIs.

Author: plashchynski

Doc/library/calendar.rst

@@ -526,6 +526,8 @@ The :mod:`calendar` module exports the following data attributes:
        >>> list(calendar.alt_month_name)
        ['', 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
 
+   .. versionadded:: next
+
 
 .. data:: alt_month_abbr
 
@@ -538,6 +540,8 @@ The :mod:`calendar` module exports the following data attributes:
        >>> list(calendar.alt_month_abbr)
        ['', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
 
+   .. versionadded:: next
+
 
 .. data:: JANUARY
           FEBRUARY

Lib/calendar.py

@@ -141,7 +141,7 @@ def __len__(self):
 month_abbr = _localized_month('%b')
 
 # Check if the platform supports %OB and %Ob specifiers
-def _is_alt_mon_available():
+def _supports_alternative_month_names():
     try:
         datetime.date(2001, 1, 1).strftime('%OB')
         datetime.date(2001, 1, 1).strftime('%Ob')
@@ -152,7 +152,7 @@ def _is_alt_mon_available():
 # On platforms that support the %OB and %Ob specifiers, it is used to get the
 # standalone form of the month name. This is required for some languages
 # such as Greek, Slavic, and Baltic languages.
-if _is_alt_mon_available():
+if _supports_alternative_month_names():
     alt_month_name = _localized_month('%OB')
     alt_month_abbr = _localized_month('%Ob')
 else:
@@ -532,7 +532,7 @@ def formatmonthname(self, theyear, themonth, withyear=True):
         if withyear:
             s = '%s %s' % (alt_month_name[themonth], theyear)
         else:
-            s = '%s' % alt_month_name[themonth]
+            s = alt_month_name[themonth]
         return '<tr><th colspan="7" class="%s">%s</th></tr>' % (
             self.cssclass_month_head, s)
 

Lib/test/test_calendar.py

@@ -561,8 +561,8 @@ def test_alt_month_name_and_abbr(self):
         # Ensure that the alternate month names and abbreviations are equal
         # to the regular month names and abbreviations for the "C" locale.
         with calendar.different_locale("C"):
-            self.assertEqual(list(calendar.month_name), list(calendar.alt_month_name))
-            self.assertEqual(list(calendar.month_abbr), list(calendar.alt_month_abbr))
+            self.assertListEqual(list(calendar.month_name), list(calendar.alt_month_name))
+            self.assertListEqual(list(calendar.month_abbr), list(calendar.alt_month_abbr))
 
     def test_locale_text_calendar(self):
         try: