Accessing the default argument values in Python

Question

How can I programmatically access the default argument values of a method in Python? For example, in the following

def test(arg1='Foo'):
    pass

how can I access the string 'Foo' inside test?

Answer 1

They are stored in test.func_defaults (python 2) and in test.__defaults__ (python 3).

As @Friedrich reminds me, Python 3 has "keyword only" arguments, and for those the defaults are stored in function.__kwdefaults__

Answer 2

Consider:

def test(arg1='Foo'):
    pass

In [48]: test.func_defaults
Out[48]: ('Foo',)

.func_defaults gives you the default values, as a sequence, in order that the arguments appear in your code.

Apparently, func_defaults may have been removed in python 3.