[Python-ideas] [Python-Dev] datetime module enhancements

[Collin Winter]

On 3/12/07, Steven Bethard <steven.bethard at gmail.com> wrote:
> [I'm not on this list, so please keep me in the CC if you reply]
>
> On 3/11/07, Collin Winter <collinw at gmail.com> wrote:
> > On 3/9/07, Steven Bethard <steven.bethard at gmail.com> wrote on python-dev:
> > > It's *not* okay to say that a date() is less than, greater than or
> > > equal to a datetime() if the year/month/day *does* match.  The correct
> > > temporal relation is During, but Python doesn't have a During
> > > operator. During is not the same as less-than, greater-than or
> > > equal-to, so all of these should be False::
> > >     datetime.datetime(2006, 1, 1, 0, 0, 0)  < datetime.date(2006, 1, 1)
> > >     datetime.datetime(2006, 1, 1, 0, 0, 0)  > datetime.date(2006, 1, 1)
> > >     datetime.datetime(2006, 1, 1, 0, 0, 0)  == datetime.date(2006, 1, 1)
> > > That is, the datetime() is not less than, greater than or equal to the
> > > corresponding date().
> > >
> > > Some discussion of these kinds of issues is here:
> > >     http://citeseer.ist.psu.edu/allen94actions.html
> > > The essence is that in order to properly compare intervals, you need
> > > the Meets, Overlaps, Starts, During and Finishes operators in addition
> > > to the Before (<) and Simulaneous (=) operators.
> > >
> > > So, let's not conflate Before, After or Simultaneous with the other
> > > relations -- if it's not strictly Before (<), After (>) or
> > > Simultaneous (=), we can just say so by returning False.
> >
> > It might be neat to add a __contains__ method to date() objects so
> > that "datetime(2007, 1, 1, 0, 0, 0) in date(2007, 1, 1)" would be
> > True. This would seem to fulfill the During operator.
>
> That's a nice idea.  With the simplest implementation, you could then
> guarantee that one of the following would always be true::
>
>     datetime < date
>     datetime in date
>     datetime > date
>
> (That would actually conflate the Starts, Finishes and During
> relations in the __contains__ operator, but I think that's a perfectly
> reasonable interpretation, and I know it would be useful in my code at
> least.)

I'll work up a patch.

Collin Winter