Mutations Hackerrank solution in Python 3

def mutate_string(string, position, character):

l1=list(string)

l1[position]=character

string=''.join(l1)

return string

if __name__ == '__main__':

s = input()

i, c = input().split()

s_new = mutate_string(s, int(i), c)

print(s_new)