Python Flask development framework easy to use notes, pythonflask

Python Flask development framework easy to use notes, pythonflask

The simplest hello world

#!/usr/bin/env python# encoding: utf-8from flask import Flaskapp = 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)

Then, access http: // localhost: 5000

Supports post/get submission

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

Multiple URLs direct

@app.route('/')@app.route('/index')

No matter whether post/get is used, the unified reception

from flask import requestargs = request.args if request.method == 'GET' else request.forma = args.get('a', 'default')

Process json requests
Request header

"Content-Type": "application/json"

Processing time:

data = request.get_json(silent=False)

Get the checkbox in post submission

{%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")

Use parameters in the url

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

End dosomething at request start
Generally, you can process database connections.

from flask import gapp = .....@app.before_requestdef before_request():  g.session = create_session()@app.teardown_requestdef teardown_request(exception):  g.session.close()

Register the filter used in the Jinja2 Template

@app.template_filter('reverse')def reverse_filter(s):  return s[::-1]

Or

def reverse_filter(s):  return s[::-1]app.jinja_env.filters['reverse'] = reverse_filter

This can be used.

def a():...def b():...FIL = {'a': a, 'b':b}app.jinja_env.filters.update(FIL)

Register the global variables used in the Jinja2 Template

JINJA2_GLOBALS = {'MEDIA_PREFIX': '/media/'}app.jinja_env.globals.update(JINJA2_GLOBALS)

Define the template and static directory used by the application

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

Use Blueprint

from flask import Blueprintbp_test = Blueprint('test', __name__)#bp_test = Blueprint('test', __name__, url_prefix='/abc')@bp_test.route('/')--------from xxx import bp_testapp = Flask(__name__)app.register_blueprint(bp_test)

Instance:

Bp_video = Blueprint ('video', _ name __, url_prefix = '/kw_news/video') @ bp_video.route ('/search/category/', methods = ['post ', 'get']) # in this case, the url_prefix in Blueprint cannot end with '/'; otherwise, 404

Use session
Cookie wrapped, no session id

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

Then

From flask import sessionsession ['somekey'] = 1session. pop ('logged _ in', None) session. clear () # expiration time, from datetime import timedeltasession implemented by cookie. permanent = Trueapp. permanent_session_lifetime = timedelta (minutes = 5)

Reverse Routing

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())

Upload files

<form action="/image/upload/" method="post" enctype="multipart/form-data"><input type="file" name="upload" />

Receive

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

Directly return an object

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

Request redirection

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!'

Obtain the user's real ip Address
Obtain from request. headers

Real_ip = request. headers. get ('x-Real-ip', request. remote_addr)
Alternatively, use the middleware document of werkzeug.

from werkzeug.contrib.fixers import ProxyFixapp.wsgi_app = ProxyFix(app.wsgi_app)return json & jsonpimport jsonfrom flask import jsonify, Response, jsondata = [] # or othersreturn 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)

Configure read Methods

# create our little application :)app = Flask(__name__)# Load default config and override config from an environment variableapp.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)------------------# configurationDATABASE = '/tmp/minitwit.db'PER_PAGE = 30DEBUG = TrueSECRET_KEY = 'development key'# create our little application :)app = Flask(__name__)app.config.from_object(__name__)app.config.from_envvar('MINITWIT_SETTINGS', silent=True)

Several uncommon Methods

from flask import abort, flashabortif not session.get('logged_in'):  abort(401)flashflash('New entry was successfully posted')

Asynchronous call
To process Asynchronization in a flask request, you can use a simple thread to process it in addition to the message system.

from threading import Threaddef async(f):  def wrapper(*args, **kwargs):    thr = Thread(target=f, args=args, kwargs=kwargs)    thr.start()  return wrapper@asyncdef dosomething(call_args):  print call_argsin 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

Project Configuration
1. Direct

app.config['HOST']='xxx.a.com'print app.config.get('HOST')

2. Environment Variables

export MyAppConfig=/path/to/settings.cfgapp.config.from_envvar('MyAppConfig')

3. Object

 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. File

# default_config.pyHOST = 'localhost'PORT = 5000DEBUG = Trueapp.config.from_pyfile('default_config.py')

EG. A create_app Method

from flask import Flask, gdef 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 appapp = create_app(settings.DEBUG)host=settings.SERVER_IPport=settings.SERVER_PORTapp.run(host=host, port=port)change log:2013-09-09 create2014-10-25 update