def username():
    user = False
    while True:
        user_name = input ("username: ")
        if not user:
            print("enter your username!")
        elif len(user_name) < 3 or len(user_name) > 8:
            print("username cannot be shorter than 3 or longer than 8. " )
        else:
            if not len(user_name) < 3 or len(user_name) > 8:
                user = True
                print("your username: ", user_name)
                return user_name
                break


def password():
    pw = False
    while True:
        pass_word = input ("password: ")
        if not pw:
            print("enter your password!")
        elif len(pass_word) < 3 or len(pass_word) > 8:
            print("password cannot be shorter than 3 or longer than 8. ")
        else:
            if not len(pass_word) < 3 or len(pass_word) > 8:
                pw = True
                print("your password: ", pass_word)
                return pass_word
                break


def reg():
    user_name = username()
    pass_word = password()
    if user_name and pass_word:
        xfile = open("test.txt", "w")
        xfile.write(user_name)
        xfile.write(pass_word)
        print("successfully registered!")
        xfile.close()


print("### register ### \n")
reg()