Created
June 21, 2011 21:55
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Django datetime
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# Python's datetime strftime doesn't handle dates before 1900. | |
# These classes override date and datetime to support the formatting of a date | |
# through its full "proleptic Gregorian" date range. | |
# | |
# Based on code submitted to comp.lang.python by Andrew Dalke | |
# | |
# >>> datetime_safe.date(1850, 8, 2).strftime("%Y/%M/%d was a %A") | |
# '1850/08/02 was a Friday' | |
from datetime import date as real_date, datetime as real_datetime | |
import re | |
import time | |
class date(real_date): | |
def strftime(self, fmt): | |
return strftime(self, fmt) | |
class datetime(real_datetime): | |
def strftime(self, fmt): | |
return strftime(self, fmt) | |
def combine(self, date, time): | |
return datetime(date.year, date.month, date.day, time.hour, time.minute, time.microsecond, time.tzinfo) | |
def date(self): | |
return date(self.year, self.month, self.day) | |
def new_date(d): | |
"Generate a safe date from a datetime.date object." | |
return date(d.year, d.month, d.day) | |
def new_datetime(d): | |
""" | |
Generate a safe datetime from a datetime.date or datetime.datetime object. | |
""" | |
kw = [d.year, d.month, d.day] | |
if isinstance(d, real_datetime): | |
kw.extend([d.hour, d.minute, d.second, d.microsecond, d.tzinfo]) | |
return datetime(*kw) | |
# This library does not support strftime's "%s" or "%y" format strings. | |
# Allowed if there's an even number of "%"s because they are escaped. | |
_illegal_formatting = re.compile(r"((^|[^%])(%%)*%[sy])") | |
def _findall(text, substr): | |
# Also finds overlaps | |
sites = [] | |
i = 0 | |
while 1: | |
j = text.find(substr, i) | |
if j == -1: | |
break | |
sites.append(j) | |
i=j+1 | |
return sites | |
def strftime(dt, fmt): | |
if dt.year >= 1900: | |
return super(type(dt), dt).strftime(fmt) | |
illegal_formatting = _illegal_formatting.search(fmt) | |
if illegal_formatting: | |
raise TypeError("strftime of dates before 1900 does not handle" + illegal_formatting.group(0)) | |
year = dt.year | |
# For every non-leap year century, advance by | |
# 6 years to get into the 28-year repeat cycle | |
delta = 2000 - year | |
off = 6 * (delta // 100 + delta // 400) | |
year = year + off | |
# Move to around the year 2000 | |
year = year + ((2000 - year) // 28) * 28 | |
timetuple = dt.timetuple() | |
s1 = time.strftime(fmt, (year,) + timetuple[1:]) | |
sites1 = _findall(s1, str(year)) | |
s2 = time.strftime(fmt, (year+28,) + timetuple[1:]) | |
sites2 = _findall(s2, str(year+28)) | |
sites = [] | |
for site in sites1: | |
if site in sites2: | |
sites.append(site) | |
s = s1 | |
syear = "%4d" % (dt.year,) | |
for site in sites: | |
s = s[:site] + syear + s[site+4:] | |
return s |
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