Using freezegun, why do pytz.utc and utcnow() output different datetimes?

Question

I'm puzzled why a function that freezes time with freezegun outputs different UTC times depending on whether datetime.datetime.utcnow() is called, or datetime.datetime.now(pytz.utc). I'm not saying it's broken, just that I don't understand why, and would like to know!

eg, using this function:

@freeze_time("2012-01-14 03:21:34", tz_offset=-4)
def test():
    print("utcnow(): %s" % datetime.datetime.utcnow())
    print("pytz.utc: %s" % datetime.datetime.now(pytz.utc))

the output is:

utcnow(): 2012-01-14 03:21:34
pytz.utc: 2012-01-13 23:21:34+00:00

I guess the first is a naive datetime, but why are they different times?

(Ultimately why I want to know: if I'm using freezegun in my tests, and I use pytz to generate times in my code being tested, I want to know what its 'correct' behaviour should be.)

Answer 1

This is an issue within freezegun see here and here.

It does not look like that this will be fixed soon. In the end I used this as a workaround:

def freezegun_utc_workaround():
    return datetime.utcnow().replace(tzinfo=pytz.utc)

For this

 datetime.datetime.now(pytz.utc)

May be it is even better to wrap this and patch it manually.