assignable expression and regex

bad_password.py

import re

def check(passwd):
    if (password_length := len(passwd)) < 1:
        return 'Need password'
    if (m := re.search(r'^%s+' % passwd[0], passwd)) and m.span()[1] == password_length:
        return '{0} contains only same character'.format(passwd)
    return '{0} is suitable for password'.format(passwd)

if __name__ == '__main__':
    print(check(''))
    print(check('aaaa'))
    print(check('aaac'))