I've had to figure this out before and I forgot it. Here it is preserved:
def daysuntilnextdow(start, next):
"""Determine how many days until the next Day of week
start: The day of the week to start from
next: The day of the week to go to
returns a number of days until the next day of week
Note, start is inclusive, so if next is the same day,
you will receive 0
Example:
>> start = 0 # Sunday
>> next = 1 # Monday
>> daysuntilnextdow(start, next)
1
>> start = 3 # Wednesday
>> next = 0 # Sunday
>> daysuntilnextdow(start, next)
4
>> start = 0 # Sunday
>> next = 0 # Sunday
>> daysuntilnextdow(start, next)
0
"""
return ((next - start) % 7)
