[Python-bugs-list] [ python-Bugs-467267 ] isinstance depends on import form (original) (raw)

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Tue, 02 Oct 2001 12:26:19 -0700

Bugs item #467267, was opened at 2001-10-02 11:56 You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=105470&aid=467267&group_id=5470

Category: Python Interpreter Core Group: Python 2.1.1 Status: Open Resolution: None Priority: 5 Submitted By: Luis P Caamano (lcaamano) Assigned to: Nobody/Anonymous (nobody) Summary: isinstance depends on import form

Initial Comment: isinstance(obj, cls) fails if cls is in a package and the import line of the obj creator is different from the import line in the code calling isinstance.

It seems to me that the problem is the address test in PyObject_IsInstance(), because different import forms produce objects with different addresses.

A limited workaround would be to test for class name but that doesn't include subclasses or types. So, instead of:

if isinstance(obj, class):

use

if obj.class.name == 'classname':

-------Sample--------------------

Python 2.1.1 (#2, Jul 25 2001, 17:54:11) [GCC 2.96 20000731 (Red Hat Linux 7.1 2.96-81)] on linux2 Type "copyright", "credits" or "license" for more information.

from spam.eggs import SpamAndEggs import spam.eggs '0x%x' % id(spam.eggs.SpamAndEggs) '0x8161ce4' '0x%x' % id(SpamAndEggs) '0x814c29c' sag = spam.eggs.SpamAndEggs() isinstance(sag, SpamAndEggs) 0 isinstance(sag, spam.eggs.SpamAndEggs) 1 sag.class <class spam.eggs.SpamAndEggs at 0x8161ce4> sag.class.name 'SpamAndEggs' SpamAndEggs.name 'SpamAndEggs' spam.eggs.SpamAndEggs.name 'SpamAndEggs'

Comment By: Guido van Rossum (gvanrossum) Date: 2001-10-02 12:26

Message: Logged In: YES user_id=6380

We need more information: please show all code involved (use the file upload, please check the checkbox or the upload won't work; you must be logged in to SourceForge as yourself).

From the session you post, it seems that there are two distinct SpamAndEggs objects, but without seeing your code it's hard to understand why.

You can respond by visiting: http://sourceforge.net/tracker/?func=detail&atid=105470&aid=467267&group_id=5470