Python的Flask开发框架简单上手笔记

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