Do deep inheritance trees degrade efficiency?

[Chris Rebert]

On Thu, Mar 19, 2009 at 2:54 AM, Christian Heimes <lists at cheimes.de> wrote:
> Chris Rebert wrote:
>> There's no effect on attribute read-writes as they all take place
>> within the single __dict__ of the instance. As for method lookup, it
>> doesn't add an indirection per se, but rather the list of classes to
>> look thru to find a method gets longer, making base-class method
>> lookups slower. IIRC, a typical method lookup does something like the
>> following pseudocode:
>>
>> for klass in the_object.__mro__:
>>     if method_name in klass.__dict__:
>>         return klass.__dict__[method_name]
>> raise AttributeError # no such attribute
>
> Your assumption is no longer true. Starting with Python 2.6 and 3.0 the
> lookup of attributes is cached. You can find detailed information by
> searching for VERSION_TAG in the source code.

Very interesting. Now that's a smart optimization; sounds a bit
similar to what V8 does for JavaScript.

Cheers,
Chris

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