Somthing strange with list as default argument

[Julien Sagnard]

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