Flask是一个基于Python开发并且依赖jinja2模板和Werkzeug WSGI服务的一个微型框架,对于Werkzeug本质是Socket服务端,其用于接收http请求并对请求进行预处理,然后触发Flask框架,开发人员基于Flask框架提供的功能对请求进行相应的处理,并返回给用户,如果要返回给用户复杂的内容时,需要借助jinja2模板来实现对模板的处理,即:将模板和数据进行渲染,将渲染后的字符串返回给用户浏览器。
“微”(micro) 并不表示你需要把整个 Web 应用塞进单个 Python 文件(虽然确实可以 ),也不意味着 Flask 在功能上有所欠缺。微框架中的“微”意味着 Flask 旨在保持核心简单而易于扩展。Flask 不会替你做出太多决策——比如使用何种数据库。而那些 Flask 所选择的——比如使用何种模板引擎——则很容易替换。除此之外的一切都由可由你掌握。如此,Flask 可以与您珠联璧合。
默认情况下,Flask 不包含数据库抽象层、表单验证,或是其它任何已有多种库可以胜任的功能。然而,Flask 支持用扩展来给应用添加这些功能,如同是 Flask 本身实现的一样。众多的扩展提供了数据库集成、表单验证、上传处理、各种各样的开放认证技术等功能。Flask 也许是“微小”的,但它已准备好在需求繁杂的生产环境中投入使用。
安装
pip install Flask
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#!/usr/bin/env python # -*- coding:utf-8 -*- from werkzeug.wrappers import Request, Response @Request.application def hello(request): return Response('Hello World!') if __name__ == '__main__': from werkzeug.serving import run_simple run_simple('localhost', 4000, hello)
一、第一次
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from flask import Flask app = Flask(__name__) @app .route( "/" ) def hello(): return "Hello World!" if __name__ = = "__main__" : app.run() |
二、路由系统
- @app.route('/user/<username>')
- @app.route('/post/<int:post_id>')
- @app.route('/post/<float:post_id>')
- @app.route('/post/<path:path>')
- @app.route('/login', methods=['GET', 'POST'])
常用路由系统有以上五种,所有的路由系统都是基于一下对应关系来处理:
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DEFAULT_CONVERTERS = { 'default' : UnicodeConverter, 'string' : UnicodeConverter, 'any' : AnyConverter, 'path' : PathConverter, 'int' : IntegerConverter, 'float' : FloatConverter, 'uuid' : UUIDConverter, } |
注:对于Flask默认不支持直接写正则表达式的路由,不过可以通过自定义来实现,见:https://segmentfault.com/q/1010000000125259
三、模板
1、模板的使用
Flask使用的是Jinja2模板,所以其语法和Django无差别
2、自定义模板方法
Flask中自定义模板方法的方式和Bottle相似,创建一个函数并通过参数的形式传入render_template,如:
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<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> </head> <body> <h1>自定义函数</h1> {{ww()|safe}} </body> </html>
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#!/usr/bin/env python # -*- coding:utf-8 -*- from flask import Flask,render_template app = Flask(__name__) def foo(): return '<h1>foo</h1>' @app .route( '/login' , methods = [ 'GET' , 'POST' ]) def login(): return render_template( 'login.html' , ww =foo ) app.run() |
四、公共组件
1、请求
对于Http请求,Flask会讲请求信息封装在request中(werkzeug.wrappers.BaseRequest),提供的如下常用方法和字段以供使用:
1 request.method 2 request.args 3 request.form 4 request.values 5 request.files 6 request.cookies 7 request.headers 8 request.path 9 request.full_path 10 request.script_root 11 request.url 12 request.base_url 13 request.url_root 14 request.host_url 15 request.host
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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)
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from flask import request from werkzeug import secure_filename @app.route('/upload', methods=['GET', 'POST']) def upload_file(): if request.method == 'POST': f = request.files['the_file'] f.save('/var/www/uploads/' + secure_filename(f.filename)) ...
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from flask import request @app.route('/setcookie/') def index(): username = request.cookies.get('username') # use cookies.get(key) instead of cookies[key] to not get a # KeyError if the cookie is missing. from flask import make_response @app.route('/getcookie') def index(): resp = make_response(render_template(...)) resp.set_cookie('username', 'the username') return resp
2、响应
当用户请求被开发人员的逻辑处理完成之后,会将结果发送给用户浏览器,那么就需要对请求做出相应的响应。
a.字符串
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@app .route( '/index/' , methods = [ 'GET' , 'POST' ]) def index(): return "index" |
b.模板引擎
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from flask import Flask,render_template,request app = Flask(__name__) @app .route( '/index/' , methods = [ 'GET' , 'POST' ]) def index(): return render_template( "index.html" ) app.run() |
c.重定向
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#!/usr/bin/env python # -*- coding:utf-8 -*- from flask import Flask, redirect, url_for app = Flask(__name__) @app .route( '/index/' , methods = [ 'GET' , 'POST' ]) def index(): # return redirect('/login/') return redirect(url_for( 'login' )) @app .route( '/login/' , methods = [ 'GET' , 'POST' ]) def login(): return "LOGIN" app.run() |
d.错误页面
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from flask import Flask, abort, render_template app = Flask(__name__) @app.route('/e1/', methods=['GET', 'POST']) def index(): abort(404, 'Nothing') app.run()
from flask import Flask, abort, render_template app = Flask(__name__) @app.route('/index/', methods=['GET', 'POST']) def index(): return "OK" @app.errorhandler(404) def page_not_found(error): return render_template('page_not_found.html'), 404 app.run()
e.设置相应信息
使用make_response可以对相应的内容进行操作
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from flask import Flask, abort, render_template,make_response app = Flask(__name__) @app .route( '/index/' , methods = [ 'GET' , 'POST' ]) def index(): response = make_response(render_template( 'index.html' )) # response是flask.wrappers.Response类型 # response.delete_cookie # response.set_cookie # response.headers['X-Something'] = 'A value' return response app.run() |
3、Session
除请求对象之外,还有一个 session 对象。它允许你在不同请求间存储特定用户的信息。它是在 Cookies 的基础上实现的,并且对 Cookies 进行密钥签名要使用会话,你需要设置一个密钥。
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设置:session['username'] = 'xxx'
- 删除:session.pop('username', None)
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from flask import Flask, session, redirect, url_for, escape, request app = Flask(__name__) @app .route( '/' ) def index(): if 'username' in session: return 'Logged in as %s' % escape(session[ 'username' ]) return 'You are not logged in' @app .route( '/login' , methods = [ 'GET' , 'POST' ]) def login(): if request.method = = 'POST' : session[ 'username' ] = request.form[ 'username' ] return redirect(url_for( 'index' )) return ''' <form action="" method="post"> <p><input type=text name=username> <p><input type=submit value=Login> </form> ''' @app .route( '/logout' ) def logout(): # remove the username from the session if it's there session.pop( 'username' , None ) return redirect(url_for( 'index' )) # set the secret key. keep this really secret: app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT' |
4.message
message是一个基于Session实现的用于保存数据的集合,其特点是:使用一次就删除
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<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> </head> <body> {% with messages = get_flashed_messages() %} {% if messages %} <ul class=flashes> {% for message in messages %} <li>{{ message }}</li> {% endfor %} </ul> {% endif %} {% endwith %} </body> </html>
from flask import Flask, flash, redirect, render_template, request app = Flask(__name__) app.secret_key = 'some_secret' @app.route('/') def index1(): return render_template('index.html') @app.route('/set') def index2(): v = request.args.get('p') flash(v) return 'ok' if __name__ == "__main__": app.run()
5.中间件
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from flask import Flask, flash, redirect, render_template, request app = Flask(__name__) app.secret_key = 'some_secret' @app .route( '/' ) def index1(): return render_template( 'index.html' ) @app .route( '/set' ) def index2(): v = request.args.get( 'p' ) flash(v) return 'ok' class MiddleWare: def __init__( self ,wsgi_app): self .wsgi_app = wsgi_app def __call__( self , * args, * * kwargs): return self .wsgi_app( * args, * * kwargs) if __name__ = = "__main__" : app.wsgi_app = MiddleWare(app.wsgi_app) app.run(port = 9999 ) |
Flask更多参见:
http://docs.jinkan.org/docs/flask/
http://flask.pocoo.org/