gh-131146: Fix month names in a genitive case in calendar module

Doc/library/calendar.rst

@@ -501,6 +501,14 @@ The :mod:`calendar` module exports the following data attributes:
  >>> list(calendar.month_name)
  ['', 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
 
+ .. caution::
+
+ In locales with alternative month names forms, the :data:`!month_name` sequence
+ may not be suitable when a month name stands by itself and not as part of a date.
+ For instance, in Greek and in many Slavic and Baltic languages, :data:`!month_name`
+ will produce the month in genitive case. Use :data:`standalone_month_name` for a form
+ suitable for standalone use.
+
 
 .. data:: month_abbr
 
@@ -512,6 +520,31 @@ The :mod:`calendar` module exports the following data attributes:
  >>> list(calendar.month_abbr)
  ['', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
 
+ .. caution::
+
+ In locales with alternative month names forms, the :data:`!month_abbr` sequence
+ may not be suitable when a month name stands by itself and not as part of a date.
+ Use :data:`standalone_month_abbr` for a form suitable for standalone use.
+
+
+.. data:: standalone_month_name
+
+ A sequence that represents the months of the year in the current locale
+ in the standalone form if the locale provides one. Else it is equivalent
+ to :data:`month_name`.
+
+ .. versionadded:: next
+
+
+.. data:: standalone_month_abbr
+
+ A sequence that represents the abbreviated months of the year in the current
+ locale in the standalone form if the locale provides one. Else it is
+ equivalent to :data:`month_abbr`.
+
+ .. versionadded:: next
+
+
 .. data:: JANUARY
  FEBRUARY
  MARCH

Lib/calendar.py

@@ -14,8 +14,9 @@
 __all__ = ["IllegalMonthError", "IllegalWeekdayError", "setfirstweekday",
  "firstweekday", "isleap", "leapdays", "weekday", "monthrange",
  "monthcalendar", "prmonth", "month", "prcal", "calendar",
- "timegm", "month_name", "month_abbr", "day_name", "day_abbr",
- "Calendar", "TextCalendar", "HTMLCalendar", "LocaleTextCalendar",
+ "timegm", "month_name", "month_abbr", "standalone_month_name",
+ "standalone_month_abbr", "day_name", "day_abbr", "Calendar",
+ "TextCalendar", "HTMLCalendar", "LocaleTextCalendar",
  "LocaleHTMLCalendar", "weekheader",
  "Day", "Month", "JANUARY", "FEBRUARY", "MARCH",
  "APRIL", "MAY", "JUNE", "JULY",
@@ -139,6 +140,16 @@ def __len__(self):
 month_name = _localized_month('%B')
 month_abbr = _localized_month('%b')
 
+# On platforms that support the %OB and %Ob specifiers, they are used
+# to get the standalone form of the month name. This is required for
+# some languages such as Greek, Slavic, and Baltic languages.
+try:
+ standalone_month_name = _localized_month('%OB')
+ standalone_month_abbr = _localized_month('%Ob')
+except ValueError:
+ standalone_month_name = month_name
+ standalone_month_abbr = month_abbr
+
 
 def isleap(year):
  """Return True for leap years, False for non-leap years."""
@@ -377,7 +388,7 @@ def formatmonthname(self, theyear, themonth, width, withyear=True):
  """
  _validate_month(themonth)
 
- s = month_name[themonth]
+ s = standalone_month_name[themonth]
  if withyear:
  s = "%s %r" % (s, theyear)
  return s.center(width)
@@ -510,9 +521,9 @@ def formatmonthname(self, theyear, themonth, withyear=True):
  """
  _validate_month(themonth)
  if withyear:
- s = '%s %s' % (month_name[themonth], theyear)
+ s = '%s %s' % (standalone_month_name[themonth], theyear)
  else:
- s = '%s' % month_name[themonth]
+ s = standalone_month_name[themonth]
  return '<tr><th colspan="7" class="%s">%s</th></tr>' % (
  self.cssclass_month_head, s)
 

Lib/test/test_calendar.py

@@ -8,6 +8,7 @@
 import io
 import locale
 import os
+import platform
 import sys
 import time
 
@@ -546,7 +547,8 @@ def test_days(self):
  self.assertEqual(value[::-1], list(reversed(value)))
 
  def test_months(self):
- for attr in "month_name", "month_abbr":
+ for attr in ("month_name", "month_abbr", "standalone_month_name",
+ "standalone_month_abbr"):
  value = getattr(calendar, attr)
  self.assertEqual(len(value), 13)
  self.assertEqual(len(value[:]), 13)
@@ -556,6 +558,38 @@ def test_months(self):
  # verify it "acts like a sequence" in two forms of iteration
  self.assertEqual(value[::-1], list(reversed(value)))
 
+ @support.run_with_locale('LC_ALL', 'pl_PL')
+ @unittest.skipUnless(sys.platform == 'darwin' or platform.libc_ver()[0] == 'glibc',
+ "Guaranteed to work with glibc and macOS")
+ def test_standalone_month_name_and_abbr_pl_locale(self):
+ expected_standalone_month_names = [
+ "", "styczeń", "luty", "marzec", "kwiecień", "maj", "czerwiec",
+ "lipiec", "sierpień", "wrzesień", "październik", "listopad",
+ "grudzień"
+ ]
+ expected_standalone_month_abbr = [
+ "", "sty", "lut", "mar", "kwi", "maj", "cze",
+ "lip", "sie", "wrz", "paź", "lis", "gru"
+ ]
+ self.assertEqual(
+ list(calendar.standalone_month_name),
+ expected_standalone_month_names
+ )
+ self.assertEqual(
+ list(calendar.standalone_month_abbr),
+ expected_standalone_month_abbr
+ )
+
+ def test_standalone_month_name_and_abbr_C_locale(self):
+ # Ensure that the standalone month names and abbreviations are
+ # equal to the regular month names and abbreviations for
+ # the "C" locale.
+ with calendar.different_locale("C"):
+ self.assertListEqual(list(calendar.month_name),
+ list(calendar.standalone_month_name))
+ self.assertListEqual(list(calendar.month_abbr),
+ list(calendar.standalone_month_abbr))
+
  def test_locale_text_calendar(self):
  try:
  cal = calendar.LocaleTextCalendar(locale='')

Misc/NEWS.d/next/Library/2025-03-17-21-21-06.gh-issue-131146.A5Obgv.rst

@@ -0,0 +1,6 @@
+Fix :class:`calendar.TextCalendar`, :class:`calendar.HTMLCalendar`,
+and the :mod:`calendar` CLI to display month names in the nominative
+case by adding :data:`calendar.standalone_month_name` and
+:data:`calendar.standalone_month_abbr`, which provide month names and
+abbreviations in the grammatical form used when a month name stands by
+itself, if the locale supports it.