[Python-Dev] Semantic of isinstance (original) (raw)

Guido van Rossum guido at python.org
Tue Jun 27 07:13:51 CEST 2006

On 6/26/06, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Phillip J. Eby wrote:

> It's not inconsistent - isinstance() checks class in addition to > type() in order to allow proxying tricks like lying about your > class. If this is a deliberate feature, it's a bit patchy, because it means the proxy can't lie about not being an instance of its real type. Perhaps Guido could clarify how much lying a proxy is supposed to be able to get away with?

Sorry, I don't remember all the constraints. Read the code and weep. This should be revisited for Py3k. The code became convoluted out of some needs in Zope; I can't remember if it was Zope 2 or Zope 3 that needed this (probably both) and I can't remember the specific situation where it was needed.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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