Hello

On python 2.3.4 and 2.4.3, 

>>> def a(x=[]):
...   return x
... 
>>> y=a()
>>> y.append(1)
>>> a()
[1]

Hence, the default argument is not recomputed. The same behavior occurs with x={} instead of x=[].

This looks like a bug because it is not coherent with 

>>> def f():
...   return []
... 
>>> y=f()
>>> y.append(5)
>>> f()
[]

So, is it a feature?

Thanks

Yes, it is. (Please post questions about Python semantics to the comp.lang.python newsgroup, they'll explain them in detail...)