[Python-Dev] About 'superobject' and descriptors (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Thu Oct 24 00:52:23 CEST 2013

On 24 Oct 2013 03:37, "hakril lse" <hakril at lse.epita.fr> wrote:

Hi, I have a question about a choice of implementation concerning 'superobject' with the descriptors. When a 'superobject' looks for a given attribute, it runs through the mro of the object. If it finds a descriptor, the 'superobject' calls the get method with 'starttype = su->objtype' as third argument (in typeobject.c: supergetattro). So, the 'type' argument of get does not give more information about the 'real calling type' in this case. It seems that this is just a redundant information of inst.class. For example: # A.descr is a descriptor # B inherit from A # C inherit from B c = C() c.descr super(C, c).descr super(B, c).descr In these 3 cases the get method is called with the same arguments that are : get(descr, c, C). If this behavior is really expected: Could you explain why ? because it means that I am missing something obvious. Because, at first sight, the 'type' argument seems to be the perfect place to get the type of the 'real calling class'.

The third argument is just there to handle the case where the instance is None (i.e. lookup directly on the class rather than an instance).

Cheers, Nick.

Thank you, -- hakril

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