app/django/utils/datetime_safe.py
author Daniel Bentley <dbentley@google.com>
Wed, 15 Apr 2009 08:01:17 +0000
changeset 2184 a1bda9afa5d0
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Step 2 of moving to new seeding model. Create Seeder class, which abstracts some seeding. Move user to Seeder class, and make new OrganizationSeeder class. If people like this, I'll finish the rest soon. Patch by: Dan Bentley

# 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