Do deep inheritance trees degrade efficiency?

Bruno Desthuilliers bruno.42.desthuilliers at websiteburo.invalid
Thu Mar 19 13:53:29 CET 2009

Chris Rebert a écrit :
> On Wed, Mar 18, 2009 at 6:09 AM, Anthra Norell <anthra.norell at> wrote:
>> Would anyone who knows the inner workings volunteer to clarify whether or
>> not every additional derivation of a class hierarchy adds an indirection to
>> the base class's method calls and attribute read-writes. In C++, I suppose,
>> a three-level inheritance would resolve into something like
>> *(*(*(*(base_class_method ())))).
> There's no effect on attribute read-writes as they all take place
> within the single __dict__ of the instance.

Except when:
- the attribute is a computed one (property or other descriptor)
- (for read access) the attribute is not set in the instance's dict.

> As for method lookup, it
> doesn't 

make much difference - the very same lookup rules apply, and it's the 
descriptor protocol (as implemented by the 'function' type) that takes 
care of returning a method object (mostly a partial application of the 
function to the instance or class) when appropriate.


> However, you shouldn't really worry about the inefficiency of a deep
> inheritance tree as Python

is probably not the right tool for the job if one have such efficiency 


> [Note: I'm purposefully ignoring the fact that methods and attributes
> are in reality looked up in the exact same way for
> simplicity/clarity.]

Ah, ok - then please don't take the above remarks as a personal offense !-)

(still posting this since it might be of interest to the OP or someone 

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