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To: python-list@python.org
From: Peter Otten <__peter__@web.de>
Subject: Re: How to see the __name__ attribute of a class by using dir()
Date: Sat, 20 Oct 2012 10:24:36 +0200
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Xref: csiph.com comp.lang.python:31800

Jennie wrote:

> The dir() built-in does not show the __name__ attribute of a class:
> 
>  >>> '__name__' in Foo.__dict__
> False
>  >>> Foo.__name__
> 'Foo'
> 
> I implementd my custom __dir__, but the dir() built-in do not want to
> call it:
> 
>  >>> class Foo:
> ...     @classmethod
> ...     def __dir__(cls):
> ...         return ['python']
> ...
>  >>> Foo.__dir__()
> ['python']
>  >>> dir(Foo)
> ['__class__', '__delattr__', '__dict__', ...]
> 
> Can someone tell me where is the problem? Thanks a lot in advance

Implementing __dir__ as an instance method works:

>>> class Foo(object):
...     def __dir__(self): return ["python"]
... 
>>> dir(Foo())
['python']

So if you want to customise dir(Foo) you have to modify the metaclass:

>>> class Foo:
...     class __metaclass__(type):
...             def __dir__(self): return ["python"]
... 
>>> dir(Foo)
['python']