On Sat, 09 Feb 2008 01:20:00 +0000, Matt Nordhoff wrote:
> Steven D'Aprano wrote:
>> Except that using has_key() means making an attribute lookup, which
>> takes time.
>
> I was going to say that, but doesn't 'in' require an attribute lookup of
> some sort too, of __contains__ or whatever?
I don't believe so. I understand that the in operator at the C level
knows about built-in types, and does something like this pseudo-code:
case type(source):
dict: return MAP_IN(source, target)
list: return LIST_IN(source, target)
str: return STR_IN(source, target)
otherwise:
return source.__contains__(target)
Except all in C, so it's fast.
I understand that the dict has_key() method is essentially a wrapper
around MAP_IN (or whatever it's actually called), and so is also fast,
just not quite as fast because of the relatively slow look-up to get to
has_key() in the first place.
--
Steven
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