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Tue Feb 10 18:25:51 CET 2009 · https://mail.python.org/pipermail/python-dev/2009-February/085970.html

Daniel Stutzbach wrote:
> On Tue, Feb 10, 2009 at 11:16 AM, Steve Holden <steve at holdenweb.com
> <mailto:steve at holdenweb.com>> wrote:
> 
>     That's true, but the same *could* be said about the existing
>     optimizations for objects that define their own __contains__.
> 
> 
> No, because there isn't a __not_contains__, so you cannot define the
> inverse operation differently.  "not a in b" and "a not in b" have
> exactly the same effects.
> 
Ah, right, that guarantees semantic equivalence. Sorry.

regards
 Steve
-- 
Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC              http://www.holdenweb.com/

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[Python-Dev] Expression optimizations