python - How to iterate over a timespan after days, hours, weeks and months?

Question

How do I iterate over a timespan after days, hours, weeks or months?

Something like:

for date in foo(from_date, to_date, delta=HOURS):
    print date

Where foo is a function, returning an iterator. I've been looking at the calendar module, but that only works for one specific year or month, not between dates.

Answer 1

Use dateutil and its rrule implementation, like so:

from dateutil import rrule
from datetime import datetime, timedelta

now = datetime.now()
hundredDaysLater = now + timedelta(days=100)

for dt in rrule.rrule(rrule.MONTHLY, dtstart=now, until=hundredDaysLater):
    print dt

Output is

2008-09-30 23:29:54
2008-10-30 23:29:54
2008-11-30 23:29:54
2008-12-30 23:29:54

Replace MONTHLY with any of YEARLY, MONTHLY, WEEKLY, DAILY, HOURLY, MINUTELY, or SECONDLY. Replace dtstart and until with whatever datetime object you want.

This recipe has the advantage for working in all cases, including MONTHLY. Only caveat I could find is that if you pass a day number that doesn't exist for all months, it skips those months.