init %C support

Author: jyalim

Lib/_strptime.py

@@ -371,6 +371,9 @@ def __init__(self, locale_time=None):
             # W is set below by using 'U'
             'y': r"(?P<y>\d\d)",
             'Y': r"(?P<Y>\d\d\d\d)",
+            # follow C99 specification of only parsing two digits for
+            # first hundred centuries
+            'C': r"(?P<C>\d\d)",
             # See gh-121237: "z" must support colons for backwards compatibility.
             'z': r"(?P<z>([+-]\d\d:?[0-5]\d(:?[0-5]\d(\.\d{1,6})?)?)|(?-i:Z))?",
             ':z': r"(?P<colon_z>([+-]\d\d:[0-5]\d(:[0-5]\d(\.\d{1,6})?)?)|(?-i:Z))?",
@@ -415,7 +418,6 @@ def __init__(self, locale_time=None):
             'Op': mapping['p'],
             'W': mapping['U'].replace('U', 'W'),
         })
-        mapping['W'] = mapping['U'].replace('U', 'W')
 
         base.__init__(mapping)
         base.__setitem__('D', self.pattern('%m/%d/%y'))
@@ -621,6 +623,15 @@ def parse_int(s):
             month = locale_time.f_month.index(found_dict['B'].lower())
         elif group_key == 'b':
             month = locale_time.a_month.index(found_dict['b'].lower())
+        elif group_key == 'C' and 'y' not in found_dict:
+            # C99 support for century in [0,99] (years 0-9999).
+            century = parse_int(found_dict[group_key])
+            year = century * 100
+            if century > 0:
+                year = century * 100
+            else:
+                # ValueError fix, since MINYEAR = 1 in Lib/_pydatetime.py
+                year = 1
         elif group_key == 'd':
             day = parse_int(found_dict['d'])
         elif group_key == 'H':

Lib/test/test_strptime.py

@@ -670,6 +670,13 @@ def test_strptime_D_format(self):
             time.strptime(test_date, "%m/%d/%y")
         )
 
+    def test_strptime_C_format(self):
+        test_century = "21"
+        self.assertEqual(
+            time.strptime(test_century, "%C").tm_year,
+            int(test_century)*100
+        )
+
 class Strptime12AMPMTests(unittest.TestCase):
     """Test a _strptime regression in '%I %p' at 12 noon (12 PM)"""
 

Lib/test/test_time.py

@@ -358,8 +358,8 @@ def test_strptime(self):
         # Should be able to go round-trip from strftime to strptime without
         # raising an exception.
         tt = time.gmtime(self.t)
-        for directive in ('a', 'A', 'b', 'B', 'c', 'd', 'D', 'F', 'H', 'I',
-                          'j', 'm', 'M', 'p', 'S', 'T',
+        for directive in ('a', 'A', 'b', 'B', 'c', 'C', 'd', 'D', 'F', 'H', 
+                          'I', 'j', 'm', 'M', 'p', 'S', 'T',
                           'U', 'w', 'W', 'x', 'X', 'y', 'Y', 'Z', '%'):
             format = '%' + directive
             if directive == 'd':