How do I construct a UTC `datetime` object in Python?

There are fixed-offset timezones in the stdlib since Python 3.2:

from datetime import datetime, timezone

t = datetime(2015, 2, 1, 15, 16, 17, 345, tzinfo=timezone.utc)

Constructor is :

datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

Docs link.

Though it is easy to implement utc timezone on earlier versions:

from datetime import tzinfo, timedelta, datetime

ZERO = timedelta(0)

class UTCtzinfo(tzinfo):
    def utcoffset(self, dt):
        return ZERO

    def tzname(self, dt):
        return "UTC"

    def dst(self, dt):
        return ZERO

utc = UTCtzinfo()
t = datetime(2015, 2, 1, 15, 16, 17, 345, tzinfo=utc)