[mod_python] Default funtion values - memory leak?

I have the following configuration:

Apache/2.0.55 (Win32) mod_python/3.2.5b Python/2.4.2

And I have a function similar to

def foo(bar=[])

During the first request, bar is [].

When execution enters the function during the second request, however, and 
no value for bar is supplied, bar is *not* [] in the function body, but 
contains the previous value!

Is that in any way expected behaviour?