请利用flask框架生成一段登录注册的python代码

以下是使用 Flask 框架生成的登录注册 Python 代码：

from flask import Flask, render_template, request, redirect, url_for, session
import hashlib

app = Flask(__name__)
app.secret_key = 'your_secret_key'

users = {
    'user1': {
        'username': 'user1',
        'password': hashlib.sha256('password1'.encode()).hexdigest()
    },
    'user2': {
        'username': 'user2',
        'password': hashlib.sha256('password2'.encode()).hexdigest()
    }
}

@app.route('/')
def index():
    if 'username' in session:
        return f'Hello, {session["username"]}!'
    else:
        return redirect(url_for('login'))

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = hashlib.sha256(request.form['password'].encode()).hexdigest()
        if username in users and users[username]['password'] == password:
            session['username'] = username
            return redirect(url_for('index'))
        else:
            return render_template('login.html', error='Invalid username or password')
    else:
        return render_template('login.html')

@app.route('/register', methods=['GET', 'POST'])
def register():
    if request.method == 'POST':
        username = request.form['username']
        password = hashlib.sha256(request.form['password'].encode()).hexdigest()
        if username in users:
            return render_template('register.html', error='Username already exists')
        else:
            users[username] = {
                'username': username,
                'password': password
            }
            session['username'] = username
            return redirect(url_for('index'))
    else:
        return render_template('register.html')

以上代码实现了基本的登录注册功能，使用了 Flask 的 session 和模板引擎。用户信息存储在一个字典中，密码使用 SHA-256 哈希算法加密。登录时检查用户名和密码是否匹配，注册时检查用户名是否已存在。