如何在Python中编写注册和登录程序？

import hashlib
import sqlite3

conn = sqlite3.connect('users.db')
c = conn.cursor()

c.execute('''CREATE TABLE IF NOT EXISTS users
             (username TEXT PRIMARY KEY, password TEXT)''')

conn.commit()

def register():
    username = input("请输入用户名: ")
    password = input("请输入密码: ")

    # 对密码进行加密
    hashed_password = hashlib.sha256(password.encode()).hexdigest()

    # 将用户名和加密后的密码插入数据库
    c.execute("INSERT INTO users VALUES (?, ?)", (username, hashed_password))
    conn.commit()

    print("注册成功！")

def login():
    username = input("请输入用户名: ")
    password = input("请输入密码: ")

    # 对密码进行加密
    hashed_password = hashlib.sha256(password.encode()).hexdigest()

    # 查询数据库中是否存在匹配的用户名和密码
    c.execute("SELECT * FROM users WHERE username=? AND password=?", (username, hashed_password))
    result = c.fetchone()

    if result:
        print("登录成功！")
    else:
        print("用户名或密码错误！")

def main():
    while True:
        choice = input("请选择操作：1. 注册  2. 登录  3. 退出\n")

        if choice == '1':
            register()
        elif choice == '2':
            login()
        elif choice == '3':
            break
        else:
            print("无效的选择！")

    conn.close()

if __name__ == '__main__':
    main()