There exists a datetime.datetime.fromtimestamp() and many a time I've wondered why there is no .totimestamp() equivalent. The answer is that not all datetime objects can be represented by a timestamp. But if you know this restriction and want it anyway, this is the magic:
Would be so cool if the docs actually mentioned this.
PS: Both functions have a utc variant too
This solution does not give you sub-second resolution, but otherwise is rather elegant. Funny thing is that the %s specifier is not documented by the stdlib, but seems to exist on the underlying implementations at least on UNIX.