[Python-bugs-list] [ python-Bugs-442758 ] 2.2a1: New style classes and __cmp__

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Bugs item #442758, was opened at 2001-07-19 07:29
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Category: type/class unification
Group: Python 2.2
>Status: Closed
Resolution: Wont Fix
Priority: 3
Submitted By: Walter Dörwald (doerwalter)
Assigned to: Guido van Rossum (gvanrossum)
Summary: 2.2a1: New style classes and __cmp__

Initial Comment:
Implementing __cmp__ in a new style class doesn't seem
to have an effect:
----
class Foo:
   def __cmp__(self, other): 
      print "foo", other
      return 0

class Bar(object):
   def __cmp__(self, other): 
      print "bar", other
      return 0

Foo() == 42
Bar() == 42
----

This only prints:
foo 42


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Comment By: Walter Dörwald (doerwalter)
Date: 2001-07-19 08:31

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OK, you're right, but I think at least the documentation 
should should mention it.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-19 08:00

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Really?  We don't warn if you define __foo__ either.

Now, a tool to aid in converting classes to the new style
might want to treat __cmp__ special. But I don't think that
the new style implementation itself ought to warn about
__cmp__.  Of course, the documentation should list all the
special methods that *are* supported -- you'll find more
differences, e.g. __getattr__ and __setattr__ work
differently, and __del__ isn't supported (yet).


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Comment By: Walter Dörwald (doerwalter)
Date: 2001-07-19 07:57

Message:
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But then some kind of warning should be issued.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-07-19 07:50

Message:
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Since __cmp__ is being phased out in favor of rich
comparisons, I would consider this a feature.  Do you agree?


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