How to mix strings in Python -

i trying write function mix strings in python getting stuck @ end. example, have 2 words, mix , pod. create function returns: pox mid

my code returns pox mix

code:

def mix_up(a, b):     if len(a , b)>1:         b=str.replace(b,b[2],a[2:3])         a=str.replace(a,a[2],b[2])         print b,"",a     return mix_up('mix','pod') 

i seeking multiple words. example:

if used dog,dinner

the output should return dig donner

thanks!

little play on string slicing

def mix_up(first, second):     new_first = second[:2] + first[2:]     new_second = first[:2] + second[2:]     return " ".join((new_first, new_second))  assert mix_up('mix','pod') == 'pox mid' assert mix_up('dog','dinner') == 'dig donner'