SF patch #691928: Use datetime in _strptime

Contributed by Brett Cannon.

To prevent code duplication, I patched _strptime to use datetime's date
object to do Julian day, Gregorian, and day of the week calculations.

Patch also includes new regression tests to test results and the
calculation gets triggered.

Very minor comment changes and the contact email are also changed.

1 files changed, 18 insertions, 56 deletions

diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index 4afc8fc5ff..55391c1f7d 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -6,32 +6,25 @@ CLASSES:
                 time information as is returned by time.strftime()
 
 FUNCTIONS:
-    firstjulian -- Calculates the Julian date up to the first of the specified
-                    year
-    gregorian -- Calculates the Gregorian date based on the Julian day and
-                    year
-    julianday -- Calculates the Julian day since the first of the year based
-                    on the Gregorian date
-    dayofweek -- Calculates the day of the week from the Gregorian date.
+    _getlang -- Figure out what language is being used for the locale
     strptime -- Calculates the time struct represented by the passed-in string
 
-Requires Python 2.2.1 or higher.
+Requires Python 2.2.1 or higher (mainly because of the use of property()).
 Can be used in Python 2.2 if the following line is added:
-    >>> True = 1; False = 0
+    True = 1; False = 0
 """
 import time
 import locale
 import calendar
 from re import compile as re_compile
 from re import IGNORECASE
+from datetime import date as datetime_date
 
 __author__ = "Brett Cannon"
-__email__ = "drifty@bigfoot.com"
+__email__ = "brett@python.org"
 
 __all__ = ['strptime']
 
-RegexpType = type(re_compile(''))
-
 def _getlang():
     # Figure out what the current language is set to.
     current_lang = locale.getlocale(locale.LC_TIME)[0]
@@ -425,7 +418,7 @@ def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
     month = day = 1
     hour = minute = second = 0
     tz = -1
-    # Defaulted to -1 so as to signal using functions to calc values
+    # weekday and julian defaulted to -1 so as to signal need to calculate values
     weekday = julian = -1
     found_dict = found.groupdict()
     for group_key in found_dict.iterkeys():
@@ -495,16 +488,21 @@ def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
                 tz = 1
             elif locale_time.timezone[2].lower() == found_zone:
                 tz = -1
-    #XXX <bc>: If calculating fxns are never exposed to the general
-    #populous then just inline calculations.  Also might be able to use
-    #``datetime`` and the methods it provides.
+    # Cannot pre-calculate datetime_date() since can change in Julian
+    #calculation and thus could have different value for the day of the week
+    #calculation
     if julian == -1:
-        julian = julianday(year, month, day)
-    else:  # Assuming that if they bothered to include Julian day it will
+        # Need to add 1 to result since first day of the year is 1, not 0.
+        julian = datetime_date(year, month, day).toordinal() - \
+                  datetime_date(year, 1, 1).toordinal() + 1
+    else:  # Assume that if they bothered to include Julian day it will
            #be accurate
-        year, month, day = gregorian(julian, year)
+        datetime_result = datetime_date.fromordinal((julian - 1) + datetime_date(year, 1, 1).toordinal())
+        year = datetime_result.year
+        month = datetime_result.month
+        day = datetime_result.day
     if weekday == -1:
-        weekday = dayofweek(year, month, day)
+        weekday = datetime_date(year, month, day).weekday()
     return time.struct_time((year, month, day,
                              hour, minute, second,
                              weekday, julian, tz))
@@ -522,39 +520,3 @@ def _insensitiveindex(lst, findme):
     else:
         raise ValueError("value not in list")
 
-def firstjulian(year):
-    """Calculate the Julian date up until the first of the year."""
-    return ((146097 * (year + 4799)) // 400) - 31738
-
-def julianday(year, month, day):
-    """Calculate the Julian day since the beginning of the year.
-    Calculated from the Gregorian date.
-    """
-    a = (14 - month) // 12
-    return (day - 32045
-            + (((153 * (month + (12 * a) - 3)) + 2) // 5)
-            + ((146097 * (year + 4800 - a)) // 400)) - firstjulian(year) + 1
-
-def gregorian(julian, year):
-    """Return 3-item list containing Gregorian date based on the Julian day."""
-    a = 32043 + julian + firstjulian(year)
-    b = ((4 * a) + 3) // 146097
-    c = a - ((146097 * b) // 4)
-    d = ((4 * c) + 3) // 1461
-    e = c - ((1461 * d) // 4)
-    m = ((5 * e) + 2) // 153
-    day = 1 + e - (((153 * m) + 2) // 5)
-    month = m + 3 - (12 * (m // 10))
-    year = (100 * b) + d - 4800 + (m // 10)
-    return [year, month, day]
-
-def dayofweek(year, month, day):
-    """Calculate the day of the week (Monday is 0)."""
-    a = (14 - month) // 12
-    y = year - a
-    weekday = (day + y + ((97 * y) // 400)
-               + ((31 * (month + (12 * a) -2 )) // 12)) % 7
-    if weekday == 0:
-        return 6
-    else:
-        return weekday-1