四、Flask 视图使用方法详细概述

from flask import Flask, request, render_template
# 创建 Flask 应用实例
app = Flask(__name__)
# 定义视图函数并绑定到 URL 路径：
@app.route('/hello')
def hello():
    return 'Hello, World!'
#运行应用程序：
if __name__ == '__main__':
    app.run()

@app.route('/submit', methods=['POST'])
def submit():
    # 处理 POST 请求
    return 'Submitted successfully'
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@app.route('/user/<username>')
def show_user_profile(username):
    # 根据用户名显示用户信息
    return f'User: {username}'

from flask import request
@app.route('/search')
def search():
    query = request.args.get('q')
    # 根据查询参数进行搜索
    return f'Search results for: {query}'

from flask import render_template
@app.route('/user/<username>')
def user_profile(username):
    # 获取用户信息
    user = get_user(username)
    # 渲染模板并传递数据
    return render_template('profile.html', user=user)

from flask import url_for
@app.route('/')
def index():
    # 构建 hello() 视图函数的 URL
    hello_url = url_for('hello')
    return f'Visit the <a href="{hello_url}">Hello</a> page.'
@app.route('/hello')
def hello():
    return 'Hello, World!'

from flask import Blueprint
### 创建蓝图对象
blueprint = Blueprint('my_blueprint', __name__)
# 在蓝图上定义视图函数
@blueprint.route('/my-page')
def my_page():
    return 'This is my page.'
# 将蓝图注册到应用实例
app.register_blueprint(blueprint)

from flask import request
@app.before_request
def before_request():
    # 在每个请求之前执行的代码
    print('Before request:', request.path)
@app.after_request
def after_request(response):
    # 在每个请求之后执行的代码
    print('After request:', response.status_code)
    return response

from flask import abort
@app.errorhandler(404)
def not_found_error(error):
    return 'Page not found.', 404
@app.route('/user/<int:user_id>')
def show_user(user_id):
    user = get_user(user_id)
    if user is None:
        abort(404)  # 如果用户不存在，返回 404 错误
    return f'User: {user.username}'

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'  # 配置数据库连接
db = SQLAlchemy(app)  # 初始化 SQLAlchemy
# 定义模型
class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
@app.route('/')
def index():
    # 查询用户数据
    users = User.query.all()
    usernames = [user.username for user in users]
    return f'Users: {", ".join(usernames)}'
if __name__ == '__main__':
    app.run()

from flask import Flask, render_template, request, redirect, url_for, flash
from flask_login import LoginManager, UserMixin, login_user, logout_user, login_required
from flask_sqlalchemy import SQLAlchemy
from flask_caching import Cache
app = Flask(__name__)
app.config['SECRET_KEY'] = 'your_secret_key'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['CACHE_TYPE'] = 'simple'
db = SQLAlchemy(app)
cache = Cache(app)
login_manager = LoginManager(app)
login_manager.login_view = 'login'
# 模型 - 用户
class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    password = db.Column(db.String(80))
    def get_id(self):
        return str(self.id)
# 用户认证回调函数
@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))
# 主页
@app.route('/')
def index():
    return 'Welcome to the Home Page'
# 登录页
@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        user = User.query.filter_by(username=username).first()
        if user and user.password == password:
            login_user(user)
            flash('Login successful!', 'success')
            return redirect(url_for('dashboard'))
        else:
            flash('Invalid username or password!', 'error')
    return render_template('login.html')
# 登出
@app.route('/logout')
@login_required
def logout():
    logout_user()
    flash('Logged out successfully!', 'success')
    return redirect(url_for('index'))
# 仪表盘，需要登录访问
@app.route('/dashboard')
@login_required
def dashboard():
    # 缓存仪表盘数据，每次访问都会从缓存中获取，有效期为 60 秒
    dashboard_data = cache.get('dashboard_data')
    if not dashboard_data:
        dashboard_data = 'Dashboard Data'
        cache.set('dashboard_data', dashboard_data, timeout=60)
    return f'Dashboard: {dashboard_data}'
if __name__ == '__main__':
    db.create_all()
    app.run()

<!DOCTYPE html>
<html>
<head>
    <title>Login Page</title>
</head>
<body>
    <h1>Login</h1>
    {% with messages = get_flashed_messages() %}
    {% if messages %}
    <ul class="messages">
        {% for message in messages %}
        <li>{{ message }}</li>
        {% endfor %}
    </ul>
    {% endif %}
    {% endwith %}
    <form action="{{ url_for('login') }}" method="POST">
        <label for="username">Username:</label>
        <input type="text" name="username" id="username" required><br>
        <label for="password">Password:</label>
        <input type="password" name="password" id="password" required><br>
        <input type="submit" value="Login">
    </form>
</body>
</html>

Flask
Flask-Login
Flask-SQLAlchemy
Flask-Caching
Flask-Flash

pip install -r requirements.txt

project/
  |- app.py
  |- templates/
      |- login.html
  |- models.py
  |- requirements.txt

from flask import Flask, request
app = Flask(__name__)
# 定义路由规则和对应的视图函数
@app.route('/')
def index():
    return 'Hello, World!'
@app.route('/user/<username>')
def user(username):
    return f'Hello, {username}!'
# 处理请求的底层逻辑
def dispatch_request():
    # 获取当前请求的 URL 和方法
    url = request.url
    method = request.method
    # 根据 URL 和方法匹配对应的视图函数
    if url == 'http://localhost:5000/':
        view_func = index
    elif url.startswith('http://localhost:5000/user/'):
        username = url.split('/')[-1]
        view_func = user
    else:
        view_func = None
    # 执行匹配到的视图函数并获取响应结果
    if view_func:
        response = view_func(username) if 'username' in locals() else view_func()
    else:
        response = '404 Not Found'
    return response
if __name__ == '__main__':
    app.run()