[Python-bugs-list] [ python-Bugs-563060 ] Module can be used as a base class

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Bugs item #563060, was opened at 2002-05-31 19:41
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Category: Python Interpreter Core
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Neal Norwitz (nnorwitz)
Assigned to: Nobody/Anonymous (nobody)
Summary: Module can be used as a base class

Initial Comment:
>From python-dev:

> But this is not what I would expect:
> 
>       >>> import string
>       >>> class newstr(string): pass
>       ... 
>       # i would have expected this to raise a TypeError
>       >>> x = newstr()
>       Traceback (most recent call last):
>         File "<stdin>", line 1, in ?
>       TypeError: 'module' object is not callable
> 
> Perhaps this error should be handled when the class
is constructed
> rather than when instantiating an object?

Guido says "the bug is that you can use any module as a
base class"

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Comment By: Phillip J. Eby (pje)
Date: 2002-05-31 20:27

Message:
Logged In: YES 
user_id=56214

More specifically, ModuleType's constructor accepts and
ignores a (name,bases,dict) call signature.  Other objects
will fail at class construction time like this:

>>> class d({}): pass

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in ?
    class d({}): pass
TypeError: dict() takes at most 1 argument (3 given)
>>> class n(1): pass

Traceback (most recent call last):
  File "<pyshell#3>", line 1, in ?
    class n(1): pass
TypeError: int() takes at most 2 arguments (3 given)
>>> class s("s"): pass

Traceback (most recent call last):
  File "<pyshell#5>", line 1, in ?
    class s("s"): pass
TypeError: str() takes at most 1 argument (3 given)
>>> 

Since the module constructor doesn't actually need any
arguments, it should complain the same way the above items do.

Interestingly, while type(module) doesn't complain when
called with excess arguments, the function 'new.module'
does.  Ironically, the docstring for new.module seems to
imply it takes an argument.  Perhaps new.module should
simply refer to type(module), once the latter is fixed.

Another, far more radical fix for this bug would be to
change the constructor to accept the (name,bases,dict)
signature, thus making it possible to subclass a module and
have it work correctly, for some value of "correctly".  :)

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