How do I replace the following occurrences of the first letter with a "*"?

Question

I got stuck on this and I don't know what to do from here.

# returns a string that changes all occurrences of its first char have been changed to '*'


def fix_start(str):
    results = []
    str.startswith(str[1])
    results = 

for example: given string = 'bubble' it should return: bu**le

Answer 1

def fix_start(s):
    return s[0]+ s[1:].replace(s[0],'*')