[New-bugs-announce] [issue5322] Python 2.6 object.__new__ argument calling autodetection faulty

[Armin Ronacher]

New submission from Armin Ronacher <armin.ronacher at active-4.com>:

In 2.6 a deprecation warning was added if `object.__new__` was called
with arguments.  Per se this is fine, but the detection seems to be faulty.

The following code shows the problem:

>>> class A(object):
...     def __new__(self):
...         raise TypeError('i do not exist')
... 
>>> class B(A):
...     __new__ = object.__new__
...     def __init__(self, x):
...         self.x = x
... 
>>> B(1)
__main__:1: DeprecationWarning: object.__new__() takes no parameters
<__main__.B object at 0x88dd0>

In the `B` case `__new__` is not overridden (in the sense that it
differs from object.__new__) but `__init__` is.  Which is the default
behaviour.  Nonetheless a warning is raised.

I used the pattern with the "__new__ switch" to achieve a
cStringIO.StringIO behavior that supports typechecks:  IterIO() returns
either a IterI or IterO object, both instances of IterIO so that
typechecks can be performed.

Real-world use case here:
http://dev.pocoo.org/projects/werkzeug/browser/werkzeug/contrib/iterio.py

----------
messages: 82497
nosy: aronacher
severity: normal
status: open
title: Python 2.6 object.__new__ argument calling autodetection faulty
type: behavior
versions: Python 2.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue5322>
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