[Python-ideas] Non-boolean return from __contains__
alexander.belopolsky at gmail.com
Tue Jul 27 18:42:02 CEST 2010
On Tue, Jul 27, 2010 at 11:59 AM, Guido van Rossum <guido at python.org> wrote:
>> So it doesn't help that 'in' may return something else than a bool
>> because the method is called on the wrong object for your purposes.
> Well that pretty much kills the proposal. I can't believe nobody
> (including myself) figured this out earlier in the thread. :-(
It may kill a use case or two, but not the proposal. In the
libraries like numpy where all python containers get replaced, this is
not an issue. Also this problem invites __rcontains__ solution, but
the proposal is not very attractive to begin with. IMO, operators
that are not symbols such as +, - or &, but words such as 'in', 'not'
or 'and' don't offer much advantage over function calls.
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