Python的Flask开发框架简单上手笔记

2020-01-04 17:57:24

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这篇文章主要介绍了Python的Flask开发框架的入门知识整理,Flask是一款极轻的Python web开发框架,需要的朋友可以参考下

最简单的hello world

#!/usr/bin/env python

# encoding: utf-8

from flask import Flask

app = Flask(__name__)

@app.route('/')

def index():

return 'hello world'

if __name__ == '__main__':

app.run(debug=True)

#app.run(host='127.0.0.1', port=8000)

之后，访问http://localhost:5000

支持post/get提交

@app.route('/', methods=['GET', 'POST'])

多个url指向

@app.route('/')

@app.route('/index')

不管post/get使用统一的接收

from flask import request

args = request.args if request.method == 'GET' else request.form

a = args.get('a', 'default')

处理json请求

request的header中

"Content-Type": "application/json"

处理时:

data = request.get_json(silent=False)

获取post提交中的checkbox

{%for page in pages %}

<tr><td><input type=checkbox name=do_delete value="{{ page['id'] }}"></td><td>

{%endfor%}

page_ids = request.form.getlist("do_delete")

使用url中的参数

@app.route('/query/<qid>/')

def query(qid):

pass

在request开始结束dosomething

一般可以处理数据库连接等等

from flask import g

app = .....

@app.before_request

def before_request():

g.session = create_session()

@app.teardown_request

def teardown_request(exception):

g.session.close()

注册Jinja2模板中使用的过滤器

@app.template_filter('reverse')

def reverse_filter(s):

return s[::-1]

或者

def reverse_filter(s):

return s[::-1]

app.jinja_env.filters['reverse'] = reverse_filter

可以这么用

def a():...

def b():...

FIL = {'a': a, 'b':b}

app.jinja_env.filters.update(FIL)

注册Jinja2模板中使用的全局变量

JINJA2_GLOBALS = {'MEDIA_PREFIX': '/media/'}

app.jinja_env.globals.update(JINJA2_GLOBALS)

定义应用使用的template和static目录

app = Flask(__name__, template_folder=settings.TEMPLATE_FOLDER, static_folder = settings.STATIC_PATH)

使用Blueprint

from flask import Blueprint

bp_test = Blueprint('test', __name__)

#bp_test = Blueprint('test', __name__, url_prefix='/abc')

@bp_test.route('/')

--------

from xxx import bp_test

app = Flask(__name__)

app.register_blueprint(bp_test)

实例:

bp_video = Blueprint('video', __name__, url_prefix='/kw_news/video')

@bp_video.route('/search/category/', methods=['POST', 'GET'])

#注意这种情况下Blueprint中url_prefix不能以 '/' 结尾, 否则404

使用session

包装cookie实现的，没有session id

app.secret_key = 'PS#yio`%_!((f_or(%)))s'

然后

from flask import session

session['somekey'] = 1

session.pop('logged_in', None)

session.clear()

#过期时间,通过cookie实现的

from datetime import timedelta

session.permanent = True

app.permanent_session_lifetime = timedelta(minutes=5)

反向路由

from flask import url_for, render_template

@app.route("/")

def home():

login_uri = url_for("login", next=url_for("home"))

return render_template("home.html", **locals())

上传文件

<form action="/image/upload/" method="post" enctype="multipart/form-data">

<input type="file" name="upload" />

接收

f = request.files.get('upload')

img_data = f.read()

直接返回某个文件

return send_file(settings.TEMPLATE_FOLDER + 'tweet/tweet_list.html')

请求重定向

flask.redirect(location, code=302) the redirect status code. defaults to 302.Supported codes are 301, 302, 303, 305, and 307. 300 is not supported.

@app.route('/')

def hello():

return redirect(url_for('foo'))

@app.route('/foo')

def foo():

return'Hello Foo!'

获取用户真实ip

从request.headers获取

real_ip = request.headers.get('X-Real-Ip', request.remote_addr)

或者, 使用werkzeug的middleware 文档

from werkzeug.contrib.fixers import ProxyFix

app.wsgi_app = ProxyFix(app.wsgi_app)

return json & jsonp

import json

from flask import jsonify, Response, json

data = [] # or others

return jsonify(ok=True, data=data)

jsonp_callback = request.args.get('callback', '')

if jsonp_callback:

return Response(

"%s(%s);" % (jsonp_callback, json.dumps({'ok': True, 'data':data})),

mimetype="text/javascript"

)

return ok_jsonify(data)

配置读取方法

# create our little application :)

app = Flask(__name__)

# Load default config and override config from an environment variable

app.config.update(dict(

DATABASE='/tmp/flaskr.db',

DEBUG=True,

SECRET_KEY='development key',

USERNAME='admin',

PASSWORD='default'

))

app.config.from_envvar('FLASKR_SETTINGS', silent=True)

------------------

# configuration

DATABASE = '/tmp/minitwit.db'

PER_PAGE = 30

DEBUG = True

SECRET_KEY = 'development key'

# create our little application :)

app = Flask(__name__)

app.config.from_object(__name__)

app.config.from_envvar('MINITWIT_SETTINGS', silent=True)

几个不常用的方法

from flask import abort, flash

abort

if not session.get('logged_in'):

abort(401)

flash

flash('New entry was successfully posted')

异步调用

想在flask的一个请求中处理异步, 除了使用消息系统, 可以用简单的线程处理

from threading import Thread

def async(f):

def wrapper(*args, **kwargs):

thr = Thread(target=f, args=args, kwargs=kwargs)

thr.start()

return wrapper

@async

def dosomething(call_args):

print call_args

in a request handler, call `dosomething`

error handler

@app.errorhandler(404)

def not_found_error(error):

return render_template('404.html'), 404

@app.errorhandler(500)

def internal_error(error):

db.session.rollback()

return render_template('500.html'), 500

项目配置

1.直接

app.config['HOST']='xxx.a.com'

print app.config.get('HOST')

2.环境变量

export MyAppConfig=/path/to/settings.cfg

app.config.from_envvar('MyAppConfig')

3.对象

class Config(object):

DEBUG = False

TESTING = False

DATABASE_URI = 'sqlite://:memory:'

class ProductionConfig(Config):

DATABASE_URI = 'mysql://user@localhost/foo'

app.config.from_object(ProductionConfig)

print app.config.get('DATABASE_URI') # mysql://user@localhost/foo

4.文件

# default_config.py

HOST = 'localhost'

PORT = 5000

DEBUG = True

app.config.from_pyfile('default_config.py')

EG. 一个create_app方法

from flask import Flask, g

def create_app(debug=settings.DEBUG):

app = Flask(__name__,

template_folder=settings.TEMPLATE_FOLDER,

static_folder=settings.STATIC_FOLDER)

app.register_blueprint(bp_test)

app.jinja_env.globals.update(JINJA2_GLOBALS)

app.jinja_env.filters.update(JINJA2_FILTERS)

app.secret_key = 'PO+_)(*&678OUIJKKO#%_!(((%)))'

@app.before_request

def before_request():

g.xxx = ... #do some thing

@app.teardown_request

def teardown_request(exception):

g.xxx = ... #do some thing

return app

app = create_app(settings.DEBUG)

host=settings.SERVER_IP

port=settings.SERVER_PORT

app.run(host=host, port=port)

change log:

2013-09-09 create

2014-10-25 update