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Title: same object, same method, but the is keyword return false.
Type: behavior Stage: resolved
Components: Versions: Python 3.6
Status: closed Resolution: not a bug
Dependencies: Superseder:
Assigned To: Nosy List: lgj1993, steven.daprano
Priority: normal Keywords:

Created on 2019-03-02 02:16 by lgj1993, last changed 2022-04-11 14:59 by admin. This issue is now closed.

Messages (2)
msg336979 - (view) Author: lgj (lgj1993) Date: 2019-03-02 02:16
>>> class A():
...   def a(self):
...       pass
>>> a = A()
>>> a is a
>>> a.a is a.a
>>> id(a.a)
>>> id(a.a)
It's seems quite oops.
msg336981 - (view) Author: Steven D'Aprano (steven.daprano) * (Python committer) Date: 2019-03-02 02:36
The ``is`` operator returns False because the two objects are different objects.

Methods are descriptors, and whenever you access an instance method, you get a brand-new method object. This is described in the documentation for descriptors:

The last two tests in your example both call id(a.a), which returns the same ID number for precisely the same reason as we explained in your previous bug report #36156. Since the two "a.a" method objects don't exist at the same time, the interpreter is permitted to re-use the same ID number for them.

P.S. remember in the previous bug report you raised, I asked you to use less awkward and confusing names? "a.a" is a terrible name, even for a simple example like this. It makes it hard to talk about what is going on when "a" is an instance and also a method.
Date User Action Args
2022-04-11 14:59:11adminsetgithub: 80344
2019-03-02 02:36:48steven.dapranosetstatus: open -> closed

nosy: + steven.daprano
messages: + msg336981

resolution: not a bug
stage: resolved
2019-03-02 02:16:43lgj1993create