作业一

def login(user, password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    try:
        return db[user] == md5.hexdigest()
    except KeyError:
        return False

作业二

def login(username, password):
    try:
        user = db[username]
        return user.password == get_md5(password + user.salt)
    except KeyError:
        return False