Are you allowed to modify func_defaults (__defaults__ in Python 3.x) in Python?

Question

I've tried doing this in Python 2.6, and it does "work":

>>> def f(i='I'): return i
...
>>> f.func_defaults = (10,)
>>> f()
10

But is this officially specified behavior, or am I hitting an implementation-specific behavior?

Answer 1

In the documentation func_defaults is documented as "writable", so it would seem to be defined behavior.