from flask import Flask     #导入类
app = Flask(__name__)       #创建类实例
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@app.route(‘/‘)             #route()装饰器来告诉flask触发函数的url
def hello_world():          #函数名称被用于生成相关联的url
    return ‘Hello, World!‘

@app.route(‘/hello‘)
def hello():
    return ‘Hello, World‘
    
@app.route(‘/user/<username>‘)   #通过把URL的一部分标记为 <variable_name> ，从而在URL中添加变量
def show_user_profile(username):
    # show the user profile for that user
    return ‘User %s‘ % escape(username)
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@app.route(‘/post/<int:post_id>‘) # 接受正整数
def show_post(post_id):
    # show the post with the given id, the id is an integer
    return ‘Post %d‘ % post_id
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@app.route(‘/path/<path:subpath>‘)  # 接受可包含斜杠的string
def show_subpath(subpath):
    # show the subpath after /path/
    return ‘Subpath %s‘ % escape(subpath)

from flask import Flask, escape, url_for
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app = Flask(__name__)
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@app.route(‘/‘)
def index():
    return ‘index‘
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@app.route(‘/login‘)
def login():
    return ‘login‘
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@app.route(‘/user/<username>‘)
def profile(username):
    return ‘{}\‘s profile‘.format(escape(username))
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with app.test_request_context():
    print(url_for(‘index‘))
    print(url_for(‘login‘))
    print(url_for(‘login‘, next=‘/‘))            #未知参数next将作为查询参数
    print(url_for(‘profile‘, username=‘John Doe‘))

from flask import request
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@app.route(‘/login‘, methods=[‘GET‘, ‘POST‘])
def login():
    if request.method == ‘POST‘:
        if valid_login(request.form[‘username‘],
                       request.form[‘password‘]):
            return log_the_user_in(request.form[‘username‘])
        else:
            error = ‘Invalid username/password‘
    else:
        return show_the_login_form()

from flask import request
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@app.route(‘/login‘, methods=[‘POST‘, ‘GET‘])
def login():
    error = None
    if request.method == ‘POST‘:
        if valid_login(request.form[‘username‘],
                       request.form[‘password‘]):
            return log_the_user_in(request.form[‘username‘])
        else:
            error = ‘Invalid username/password‘
    # the code below is executed if the request method
    # was GET or the credentials were invalid
    return render_template(‘login.html‘, error=error)

url_for(‘static‘, filename=‘style.css‘) #静态文件
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@app.route(‘/hello/‘)
@app.route(‘/hello/<name>‘)
def hello(name=None):
    return render_template(‘hello.html‘, name=name) #html文件渲染

from flask import abort, redirect, url_for
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@app.route(‘/‘)
def index():
    return redirect(url_for(‘login‘))
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@app.route(‘/login‘)
def login():
    abort(401)                   #401表示禁止访问
    this_is_never_executed()
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@app.errorhandler(404)           #errorhandler装饰器定制出错页面
def page_not_found(error):       #404表示页面不存在
    return render_template(‘page_not_found.html‘), 404