Where is the default parameter in Python function

Question

I think many people have seen the python\'s function which receives default parameters. For example:

def foo(a=[]):
    a.append(3)
    return a

Answer 1

It's in the function object, in the func_defaults:

def f(a=[]): a.append(3)

print f.func_defaults # ([],)

f()

print f.func_defaults # ([3],)