Flaskrouting and 视graphfunction

1. routing basicconcepts

routing is URL to 视graphfunction maprelationships. in Flaskin, 我们using装饰器来定义routing. 当user访问某个URL时, Flask会根据routing规则调用 for 应 视graphfunction, 并将function return valueserving asresponse返回给客户端.

1.1 basicrouting定义

using@app.route()装饰器可以定义一个routing:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def index():
    return 'Hello, Flask!'

@app.route('/about')
def about():
    return 'About Page'

if __name__ == '__main__':
    app.run(debug=True)

in on 面 例子in, 我们定义了两个routing:

• / map to index() function
• /about map to about() function

2. URL规则

Flasksupport many 种URL规则, including静态routing, 动态routing and URL转换器etc..

2.1 静态routing

静态routing is 指URLpath固定不变 routing:

@app.route('/contact')
def contact():
    return 'Contact Page'

2.2 动态routing

动态routing is 指URLpathinpackage含variable routing. using尖括号<>可以定义动态routing:

@app.route('/user/')
def user_profile(username):
    return f'User Profile: {username}'

当user访问/user/john时, Flask会调用user_profile('john')function, 并返回"User Profile: john".

2.3 URL转换器

Flaskproviding了 many 种URL转换器, 用于指定variable class型:

转换器	describes	example
string	stringclass型 (默认) , 不package含斜杠	/user/<string:username>
int	整数class型	/post/<int:post_id>
float	浮点数class型	/product/<float:price>
path	stringclass型, package含斜杠	/file/<path:file_path>
uuid	UUIDclass型	/item/<uuid:item_id>

2.3.1 usingURL转换器 example

@app.route('/post/')
def show_post(post_id):
    return f'Post ID: {post_id}'

@app.route('/product/')
def product_by_price(price):
    return f'Product Price: ${price}'

@app.route('/file/')
def get_file(file_path):
    return f'File Path: {file_path}'

3. 视graphfunction

视graphfunction is processingrequest并返回response function. in Flaskin, 视graphfunction可以返回 many 种class型 response:

3.1 返回string

视graphfunction可以直接返回string, Flask会将其serving asresponse体返回:

@app.route('/')
def index():
    return 'Hello, Flask!'

3.2 返回HTML

视graphfunction可以返回HTMLstring, Flask会将其serving asHTMLresponse返回:

@app.route('/html')
def html_response():
    return '<h1>Hello, HTML!</h1><p>This is an HTML response.</p>'

3.3 返回JSON

usingjsonify()function可以返回JSONresponse:

from flask import jsonify

@app.route('/json')
def json_response():
    data = {
        'name': 'John',
        'age': 30,
        'city': 'New York'
    }
    return jsonify(data)

3.4 返回重定向

usingredirect()function可以返回重定向response:

from flask import redirect

@app.route('/old-url')
def old_url():
    return redirect('/new-url', code=302)

@app.route('/new-url')
def new_url():
    return 'This is the new URL'

3.5 返回errorresponse

usingabort()function可以返回errorresponse:

from flask import abort

@app.route('/error')
def error():
    abort(404)  # 返回404error

@app.route('/forbidden')
def forbidden():
    abort(403)  # 返回403error

3.6 自定义error页面

using@app.errorhandler()装饰器可以自定义error页面:

@app.errorhandler(404)
def page_not_found(error):
    return '<h1>404 - Page Not Found</h1><p>The requested page does not exist.</p>', 404

@app.errorhandler(500)
def internal_server_error(error):
    return '<h1>500 - Internal Server Error</h1><p>Something went wrong on the server.</p>', 500

4. requestmethod

默认circumstances under , Flaskrouting只processingGETrequest. usingmethodsparameter可以指定routingprocessing requestmethod:

4.1 processing many 种requestmethod

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        # processingPOSTrequest, 例such asprocessing表单submitting
        username = request.form['username']
        password = request.form['password']
        # verificationuser名 and password
        return f'Login successful for {username}'
    else:
        # processingGETrequest, 例such as显示login表单
        return '<h1>Login Page</h1><form method="post">Username: <input type="text" name="username"><br>Password: <input type="password" name="password"><br><input type="submit" value="Login"></form>'

4.2 专门 装饰器

Flask 0.6及以 on versionproviding了专门 装饰器来processing不同 requestmethod:

from flask import request

@app.get('/login')
def login_get():
    # processingGETrequest
    return '<h1>Login Page</h1><form method="post">Username: <input type="text" name="username"><br>Password: <input type="password" name="password"><br><input type="submit" value="Login"></form>'

@app.post('/login')
def login_post():
    # processingPOSTrequest
    username = request.form['username']
    password = request.form['password']
    return f'Login successful for {username}'

5. URL构建

usingurl_for()function可以根据视graphfunction名构建URL:

5.1 basic用法

from flask import url_for

@app.route('/')
def index():
    # 构建URL for 'about' view function
    about_url = url_for('about')
    return f'<a href="{about_url}">About</a>'

@app.route('/about')
def about():
    return 'About Page'

5.2 带 has parameter URL构建

for 于带 has parameter routing, 可以through关键字parameter传递parameter值:

@app.route('/user/')
def user_profile(username):
    return f'User Profile: {username}'

@app.route('/url-build')
def url_build():
    # 构建URL with parameter
    user_url = url_for('user_profile', username='john')
    return f'<a href="{user_url}">John\'s Profile</a>'

5.3 静态fileURL

usingurl_for('static', filename='filename')可以构建静态file URL:

@app.route('/static-url')
def static_url():
    css_url = url_for('static', filename='style.css')
    js_url = url_for('static', filename='script.js')
    return f'CSS: <link rel="stylesheet" href="{css_url}"><br>JS: <script src="{js_url}"></script>'

6. 蓝graph (Blueprints)

蓝graph is Flaskin用于组织routing 一种方式, 适合 big 型application. using蓝graph可以将application分 for many 个module, 每个module has 自己 routing, 视graphfunction and 模板.

6.1 creation蓝graph

首先, creation一个蓝graphobject:

from flask import Blueprint

# creation蓝graph, 第一个parameter is 蓝graph 名称, 第二个parameter is 蓝graphwhere module
blog_bp = Blueprint('blog', __name__)

6.2 in 蓝graphin定义routing

using蓝graphobject route()method定义routing:

@blog_bp.route('/')
def blog_index():
    return 'Blog Index'

@blog_bp.route('/post/')
def blog_post(post_id):
    return f'Blog Post: {post_id}'

6.3 register蓝graph

in Flaskapplicationinregister蓝graph:

from flask import Flask
from blog import blog_bp  # import蓝graph

app = Flask(__name__)

# register蓝graph, url_prefixparameter指定蓝graph URL before 缀
app.register_blueprint(blog_bp, url_prefix='/blog')

register after , 蓝graphin定义 routing会被添加 to applicationin, URL会自动添加/blog before 缀:

• /blog/ map to blog_index() function
• /blog/post/1 map to blog_post(1) function

6.4 蓝graph 模板 and 静态file

蓝graph可以 has 自己 模板 and 静态fileTable of Contents:

# creation蓝graph时指定模板 and 静态fileTable of Contents
blog_bp = Blueprint('blog', __name__, 
                    template_folder='templates',
                    static_folder='static')

in 蓝graph 视graphfunctioninusing模板:

from flask import render_template

@blog_bp.route('/')
def blog_index():
    return render_template('blog/index.html')

7. routing advanced features

7.1 子域名routing

Flasksupport子域名routing, 可以throughsubdomainparameter指定子域名:

app.config['SERVER_NAME'] = 'example.com'

@app.route('/', subdomain='admin')
def admin_index():
    return 'Admin Index'

当访问admin.example.com时, 会调用admin_index()function.

7.2 重定向routing

可以usingredirect_toparametercreation重定向routing:

@app.route('/old', redirect_to='/new')
def old_route():
    # 这个function不会被调用, 因 for request会被重定向 to /new
    pass

@app.route('/new')
def new_route():
    return 'This is the new route'

7.3 routing别名

可以usingendpointparameter for routing指定别名:

@app.route('/home', endpoint='index')
def home():
    return 'Home Page'

usingurl_for('index')会生成/home URL.

8. request on under 文

Flaskproviding了request on under 文, 用于访问request相关 information. 常用 request on under 文variableincluding:

8.1 request

requestobjectpackage含了request 所 has information:

from flask import request

@app.route('/request-info')
def request_info():
    return f'''Request Method: {request.method}<br>
               Request URL: {request.url}<br>
               Request Headers: {request.headers}<br>
               Request Args: {request.args}<br>
               Request Form: {request.form}<br>
               Request Files: {request.files}'''

8.2 session

sessionobject用于storeusersessiondata:

from flask import session

app.secret_key = 'your-secret-key'

@app.route('/set-session')
def set_session():
    session['username'] = 'john'
    return 'Session set'

@app.route('/get-session')
def get_session():
    username = session.get('username', 'Guest')
    return f'Username: {username}'