how to set default value to function call in python code example

Example 1: python function parameters default value

def F(a, b=None):
    if b is None:
        b = []
    b.append(a)
    return b

Example 2: python default function value

def munge(sep: AnyStr = None): ...
def munge(input: AnyStr, sep: AnyStr = None, limit=1000): ...