import hashlib

db = {}

def to_md5(password):
    md5 = hashlib.md5()
    md5.update(password.encode('utf-8'))
    return md5.hexdigest()

def register(name,pw):
    db['user'] = name
    db['password'] = to_md5(pw)    

def login(n,p):
    p = to_md5(p)
    if n == db['user'] and p == db['password']:
        print('Hi:%s! welcome back!' % db['user'])
    else:
        print('username or password is fault!')

register('jay','123456')
login('jay','123456')