结合实际场景又加了点东西

import hashlib
def calc_md5(password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    return md5.hexdigest()
db = {}

def register(username, password):
    db[username] = calc_md5(password+username+'the-salt')

def login(username, password):
    if username in db:
        return 1 if db.get(username) == calc_md5(password+username+'the-salt') else 0
    else:
        return 0

# register
while True:
    username = input('please input your username: ')
    if username not in db:
        break
    else:
        print('The username has already exists ,please try another!')
while True:
    password1 = input('please input your password : ')
    password2 = input('please input your passwird again :')
    if password1 == password2:
        break
    else:
        print('The password you entered two times is not consistent , please retry!')
register(username, password2)

#login
while True:
    login_name = input('please input your username :')
    login_password = input('please input your password :')
    login_result = login(login_name, login_password)
    if login_result == 1:
        print('login sucessfully!')
        break
    else:
        print('username or password is wrong please retry!')