A valid username

A valid username

There are some websites registered users, will have a user name length limit, between ~ 18 (including) bits such as the length of the user name must be between 6 (inclusive).

Please implemented program
with function to achieve the legitimacy of the user name to be checked.

def check_username(username):
    if 6<=len(str(username))<=18:
        return True
    else:
        return False
user=input
print(check_username(user))