Differenz in Tagen zwischen zwei Datumsangaben ermitteln.

#!/usr/bin/env python
# $Id: datediff,v 1.3 2013/09/14 14:37:31 elias Exp $

from datetime import date
from re import match
from sys import argv

opt_year_real = False
opt_short_output = False

def twodigityear(y):
    if y > 100 or opt_year_real:
        return y
    if y > 70:
        y += 1900
    else:
        y += 2000
    return y

def s2date(s):
    mo = match(r'(\d{,2})\.(\d{,2})\.(\d+)$', s)
    if mo:
        year = twodigityear(int(mo.group(3)))
        return date(year, int(mo.group(2)), int(mo.group(1)))
    mo = match(r'(\d+)\-(\d{,2})\-(\d{,2})$', s)
    if mo:
        year = twodigityear(int(mo.group(1)))
        return date(year, int(mo.group(2)), int(mo.group(3)))
    raise RuntimeError, 'Unsupported date format'

argc = len(argv)
if argc == 2:
    d1 = date.today()
    d2 = s2date(argv[1])
elif argc == 3:
    d1 = s2date(argv[1])
    d2 = s2date(argv[2])
else:
    raise RuntimeError, 'Improper parameters'

dd = d2 - d1
days = dd.days
if opt_short_output:
    print(days)
else:
    direction = 'after'
    ds1 = d1.isoformat()
    ds2 = d2.isoformat()
    if days < 0:
        direction = 'before'
        days = abs(days)
    if days > 1:
        plural = 'days'
    else:
        plural = 'day'
    print('%s is %d %s %s %s' % (ds2, days, plural, direction, ds1))