Somthing strange with list as default argument

From: Julien Sagnard (julien.sagnard.withoutthis_at_free.fr)
Date: 09/22/04 

Date: Wed, 22 Sep 2004 10:19:45 +0200

Hi all,

When passing a list as default argument for a function, only one list is
created for all calls.
exemple:
>>> def f(a=[]):
... a.append("x")
... print a
...
>>> f()
['x']
>>> f()
['x', 'x']
>>> f()
['x', 'x', 'x']
>>> f()
['x', 'x', 'x', 'x']
>>>

I'm not found any reference of this. Is it a bug ?
I'm working on Windows 2000 with python 2.3.4

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