Finding the date of the next Saturday

How would one go about finding the date of the next Saturday in Python? Preferably using datetime and in the format '2013-05-25'?

>>> from datetime import datetime, timedelta
>>> d = datetime.strptime('2013-05-27', '%Y-%m-%d') # Monday
>>> t = timedelta((12 - d.weekday()) % 7)
>>> d + t
datetime.datetime(2013, 6, 1, 0, 0)
>>> (d + t).strftime('%Y-%m-%d')
'2013-06-01'

I use (12 - d.weekday()) % 7 to compute the delta in days between given day and next Saturday because weekday is between 0 (Monday) and 6 (Sunday), so Saturday is 5. But:

• 5 and 12 are the same modulo 7 (yes, we have 7 days in a week :-) )
• so 12 - d.weekday() is between 6 and 12 where 5 - d.weekday() would be between 5 and -1
• so this allows me not to handle the negative case (-1 for Sunday).

Here is a very simple version (no check) for any weekday:

>>> def get_next_weekday(startdate, weekday):
    """
    @startdate: given date, in format '2013-05-25'
    @weekday: week day as a integer, between 0 (Monday) to 6 (Sunday)
    """
    d = datetime.strptime(startdate, '%Y-%m-%d')
    t = timedelta((7 + weekday - d.weekday()) % 7)
    return (d + t).strftime('%Y-%m-%d')

>>> get_next_weekday('2013-05-27', 5) # 5 = Saturday
'2013-06-01'