[Python-Dev] datetime module enhancements

Sat Mar 10 02:26:17 CET 2007

On 2007年3月10日, Greg Ewing wrote:
> Collin Winter wrote:
> > Treat dates as if they have a time-part of midnight. This is my preferred
> > solution, and it is already what the datetime module does, for example,
> > when subtracting two dates.
>> Does it really? Seems to me you can pick any time of day
> to be the representative time and get the same result
> when subtracting two dates, as long as you pick the same
> one for both dates. So it's not really assuming anything
> here.

It certainly gives that appearance:
 >>> from datetime import datetime
 >>> datetime(2007, 1, 2) - datetime(2007, 1, 1, 0, 0, 0)
 datetime.timedelta(1)
 >>> str(_)
 '1 day, 0:00:00'
The behaviour to the end user exposes the midnight assumption,
regardless whether it's explained by saying the constructor
makes the assumption or the subtraction makes the assumption.
-- ?!ng