ABCs -> infix syntax for isinstance() ?
Terry Reedy
tjreedy at udel.edu
Fri Oct 3 18:41:14 EDT 2008
Boris Borcic wrote:
> Given the ABC innovation, maybe an infix syntax for isinstance() would
> be good.
>
> Possibilities :
>
> - stealing "is" away from object identity. As a motivation, true use
> cases for testing object identity are rare; forcing the usage of a
> function or method to test it, would dissuade abuse.
>
> - allowing containment tests, ie "x in Number" to invoke isinstance() in
> the background when the container is of type <type>. My brain is too
> muddled by flu at the moment, to see whether Guido's fabled time machine
> allowed him to already provide all the necessities in py26.
> Any takers ?
I believe this could be done by adding a __contains__ method to type.
(It does not have one now). Then x in X should work for all classes
that are instances of type or a subclass thereof.
> - combining both keywords to create a third one, eg "is in"
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