why is self not passed to id()?
Maric Michaud
maric at aristote.info
Thu Sep 4 16:44:53 EDT 2008
Le Thursday 04 September 2008 22:26:53 Ruediger, vous avez écrit :
> Hello!
>
Hello,
> Executing following little program gives me an TypeError.
>
> What makes me wonder is that foo does get an argument passed while bar
> doesn't. Can anyone explain why??????
>
Because id is a builtin written in the core language and doesn't subscribe to
the descritpor protocol python functions has.
>
> class foo(list):
> __hash__ = lambda x: id(x)
>
Wow ! You are really going on trouble with this, believe me there is a real
good reason for list not to be hashable. A dictionnary or set containing some
of your foo is virtually inconsistent, read carefully the manual about
prerequesites for dict keys, they *need* to be immutable.
> class bar(list):
> __hash__ = id
>
> _s_ = set()
> _s_.add(foo())
> _s_.add(bar())
>
> rue at linux:~> python test01.py
> Traceback (most recent call last):
> File "test01.py", line 9, in <module>
> _s_.add(bar())
> TypeError: id() takes exactly one argument (0 given)
>
> --
> http://mail.python.org/mailman/listinfo/python-list
--
_____________
Maric Michaud
_____________
Aristote - www.aristote.info
3 place des tapis
69004 Lyon
Tel: +33 4 26 88 00 97
Mobile: +33 6 32 77 00 21
More information about the Python-list
mailing list