PyConZA 2013: "An Introduction to Flask" by Adrianna Pińska

Introduction to web applications with Flask Adrianna Pi´ nska1 October
5, 2013 [email protected]

What is Flask? Simple web framework Similar projects: web.py Bottle
Uses: Werkzeug (WSGI) Jinja 2 (templating)

Why Flask? Clean syntax Little boilerplate Easy to set up

Hello world from flask import Flask app = Flask(__name__) @app.route("/")
def hello (): return "Hello World!" if __name__ == "__main__": app.run()

Templates Jinja 2 Other engines: Genshi

Jinja example @app.route("/") def hello (): return render_template ( ’foo.html
’, message="Hello World!" ) <!doctype html > <link rel="stylesheet" href= "{{ url_for(’static ’, filename=’styles.css ’)}}"> <p id="message">{{ message }}</p>

URL variables @app.route("/") @app.route("/<message >") def hello(message="Hello World!"): return render_template
( ’foo.html ’, message=message )

POST / GET parameters @app.route(’/’, methods =[’GET’, ’POST ’]) def
hello (): return render_template ( ’foo.html ’, message=request.args.get( ’message ’, "Hello world!") )

Sessions (1) @app.route("/") def hello (): if ’message ’ in
session: message = session[’message ’] else: message = "Hello world!" return render_template ( ’foo.html ’, message=message )

Sessions (2) @app.route("/<message >") def put_message(message ): session[’message ’] =
message return render_template ( ’foo.html ’, message="Message ’%s’ saved!" % message ) app.secret_key = ’super secret random string ’

Sessions (3) Size limit: 4K Server-side sessions Recreate objects

Make it do stuﬀ Local scripting Forms AJAX

AJAX (1) <p id="scramble">Scramble!</p> <script >$SCRIPT_ROOT = {{ request.script_root |tojson|safe
}};</script > <script src="{{ url_for(’static ’, filename=’jquery.js ’) }}"></script > <script src="{{ url_for(’static ’, filename=’myscript.js ’)}}"></script >

AJAX (2) $(function () { $(’#scramble ’). bind(’click ’, function
() { $.getJSON($SCRIPT_ROOT + ’/_scramble ’, { message: $("#message"). text () }, function(data) { $("#message"). text(data.scrambled ); }); return false; }); });

AJAX (3) @app.route(’/_scramble ’) def scramble (): message = request.args.get(’message
’) l = list(message) random.shuffle(l) scrambled = ’’.join(l) return jsonify(scrambled=scrambled)

More information http://ﬂask.pocoo.org/ #pocoo on Freenode

PyConZA 2013: "An Introduction to Flask" by Adr...

PyConZA 2013: "An Introduction to Flask" by Adrianna Pińska

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Introduction to web applications with Flask Adrianna Pi´ nska1 October

What is Flask? Simple web framework Similar projects: web.py Bottle

Why Flask? Clean syntax Little boilerplate Easy to set up

Hello world from flask import Flask app = Flask(name) @app.route("/")

Templates Jinja 2 Other engines: Genshi

Jinja example @app.route("/") def hello (): return render_template ( ’foo.html

URL variables @app.route("/") @app.route("/<message >") def hello(message="Hello World!"): return render_template

POST / GET parameters @app.route(’/’, methods =[’GET’, ’POST ’]) def

Sessions (1) @app.route("/") def hello (): if ’message ’ in

Sessions (2) @app.route("/<message >") def put_message(message ): session[’message ’] =

Sessions (3) Size limit: 4K Server-side sessions Recreate objects

Make it do stuﬀ Local scripting Forms AJAX

AJAX (1) <p id="scramble">Scramble!</p> <script >$SCRIPT_ROOT = {{ request.script_root |tojson|safe

AJAX (2) $(function () { $(’#scramble ’). bind(’click ’, function

AJAX (3) @app.route(’/_scramble ’) def scramble (): message = request.args.get(’message

More information http://ﬂask.pocoo.org/ #pocoo on Freenode