[Python-Dev] __contains__ hook

[Moshe Zadka]

On Thu, 3 Feb 2000, Fred L. Drake, Jr. wrote:

>  > I totally agree with Guido -- for me, the whole point of this hack is
>  > to avoid people asking for 'in' in dicts: this way we can code a class
> 
>   That's not a good enough reason to add it.

Well, it the metaphorical sense it is -- the reason people were asking for
'in' in dicts were usually because they wanted to use dictionaries as
sets. Not having a way to express with 'in' certainly seems like a wart.

>  > I'm not quite sure where we want to put the C API version of __contains__
>  > - I'd add a tp_as_set, but the only method seems to be 'in', so it seems
>  > like a waste of valuable real-estate before we are driven into
>  > non-backwards-compatability. I think I should at least ask permission from
>  > the owner before I move over there, trampling everything in my way<wink>
> 
>   I suspect there will be fairly few set implementations in C; there
> will be something like a dictionary (kjSet might be updated, for
> instance), but that's probably about it.
>   The "in"/"not in" operation can work off the contains slot, and I
> expect set union would be expressed as +, which is already in the
> as_number structure.  Everything else should probably be implemented
> as a method or a function rather than as an operator overload.

Fred, I'm afraid I didn't understand you /at all/. Can you just say what 
is it you're offering? There isn't a "contains" slot right now, and what
I'm wondering is where to put it.
--
Moshe Zadka <mzadka@geocities.com>. 
INTERNET: Learn what you know.
Share what you don't.