Days between two dates?

Try:

(b-a).days

I tried with b and a of type datetime.date.

Do you mean full calendar days, or groups of 24 hours?

For simply 24 hours, assuming you're using Python's datetime, then the timedelta object already has a days property:

days = (a - b).days

For calendar days, you'll need to round a down to the nearest day, and b up to the nearest day, getting rid of the partial day on either side:

roundedA = a.replace(hour = 0, minute = 0, second = 0, microsecond = 0)
roundedB = b.replace(hour = 0, minute = 0, second = 0, microsecond = 0)
days = (roundedA - roundedB).days

Assuming you’ve literally got two date objects, you can subtract one from the other and query the resulting timedelta object for the number of days:

>>> from datetime import date
>>> a = date(2011,11,24)
>>> b = date(2011,11,17)
>>> a-b
datetime.timedelta(7)
>>> (a-b).days
7

And it works with datetimes too — I think it rounds down to the nearest day:

>>> from datetime import datetime
>>> a = datetime(2011,11,24,0,0,0)
>>> b = datetime(2011,11,17,23,59,59)
>>> a-b
datetime.timedelta(6, 1)
>>> (a-b).days
6