第一题:

import hashlib
def login(user, password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    if db[user] and db[user]==md5.hexdigest():
        return True
    else:
        return False

第二题:

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