>>> (t - epoch) // timedelta(seconds=1)

I don't like this syntax, because I can't guess the result unit:
  datetime - datetime -> timedelta
but:
  timedelta / timedelta -> seconds? days? nanoseconds?

If you example, you used timedelta(seconds=1), but what is the result 
unit if you use timedelta(hours=1)? or timedelta(days=1, 
microseconds=1)?

The problem is that timedelta has no unit (or has multiple units), 
whereas timedelta.toseconds() are seconds. So about your example:

>>> (t - epoch).toseconds()
--> fractional seconds
>>> int((t - epoch).toseconds())
--> whole seconds