Number of seconds since the beginning of the day UTC timezone

Here's one way to do it.

from datetime import datetime, time

utcnow = datetime.utcnow()
midnight_utc = datetime.combine(utcnow.date(), time(0))
delta = utcnow - midnight_utc
print delta.seconds # <-- careful

EDIT As suggested, if you want microsecond precision, or potentially crossing a 24-hour period (i.e. delta.days > 0), use total_seconds() or the formula given by @unutbu.

print delta.total_seconds()  # 2.7
print delta.days * 24 * 60 * 60 + delta.seconds + delta.microseconds / 1e6 # < 2.7

The number of seconds in a datetime.timedelta, x, is given by timedelta.total_seconds:

x.total_seconds()

This function was introduced in Python2.7. For older versions of python, you just have to compute it yourself: total_seconds = x.days*24*60*60 + x.seconds + x.microseconds/1e6.