Flask restfulservices

Flask RESTful ServicesThere is an alternative to DJango

http://flask.pocoo.org/

Who Am I?

Why Flask?

SimpleIntuitiveLoads of Extensions

Pythonic

Hello World in 3 Steps

from flask import Flask, jsonifyapp = Flask(__name__)

@app.route("/")def root(): msg = {"message": "Hello World"} return jsonify(msg)

if __name__ == "__main__": app.run()

1. Creation of the Flask App

2. Define Route

3. Return dictionary as JSON

1. Response

Simple Response

@app.route("/simple/")def return_simple(): return "I lost it", 404

Returning a Generator

@app.route("/generator/")def return_generator(): def loads_of_data(): yield "[" for i in xrange(5): if i: yield "," yield '{ "key%d": "Entry Number %d"}' % (i, i) yield "]" return Response(loads_of_data(), content_type="application/json")

Generator Function

Returning a Response

@app.route("/response/")def return_response(): msg = {"message": "I am working on that..."} msg_json = json.dumps(msg) return Response(msg_json, content_type="application/json", status=202)

class flask.Response(response=None, status=None, headers=None, mimetype=None,content_type=None, direct_passthrough=False)

Returning a File

@app.route("/file/")def return_file(): return send_file('flask_logo.png')

flask.send_file(filename_or_fp, mimetype=None, as_attachment=False,attachment_filename=None, add_etags=True, cache_timeout=None,conditional=False)

2. Routing

Dynamic Route

@app.route("/car/<make>/<model>")def car(make, model): car = { "make": make, "model": model } return jsonify(car)

Dynamic Route - Set Type

@app.route("/car/<string:make>/<int:model>")def car(make, model): car = { "make": make, "model": model } return jsonify(car)

Specify type of params

Dynamic Route - Set Default

@app.route("/car/<string:make>/<int:model>")@app.route("/car/<string:make>/", defaults={"model": 500})@app.route("/car/", defaults={"make": "Fiat", "model": 500})def car(make, model): car = { "make": make, "model": model } return jsonify(car)

REST Verbs

@app.route("/inventory/", methods=['POST'])def inventory_post(): data = request.json resp = jsonify({"idinput": data.get("id")}) resp.status_code = 201 return resp

methods allow a list of verbs

jsonify returns a Response object

Talk is Cheap...

3. Advance-ish

Static File Server

@app.route('/<path:path>')def send_app(path): return send_from_directory('www/', path)

@app.route('/')def send_app_index(): return send_from_directory('www/', 'index.html')

Database Connectionfrom flask import g

def get_db(): db = getattr(g, '_database', None) if db is None: db = g._database = connect_to_database() return db

@app.teardown_appcontextdef close_connection(exception): db = getattr(g, '_database', None) if db is not None: db.close()

http://flask.pocoo.org/docs/0.10/patterns/sqlite3/

Use Flask’s Global Object

Open connection if not connected

Close connection when request is done

Exception Handling

def restful_error_handler(ex): resp = jsonify(error_message=str(ex)) if isinstance(ex, HTTPException): resp.status_code = ex.code else: resp.status_code = 500 return resp

for code in default_exceptions.iterkeys(): app.error_handler_spec[None][code] = restful_error_handler

http://flask.pocoo.org/snippets/83/

Set Response Code

[<blueprint name>][<http code>]

Blueprint

bp = Blueprint('car', __name__)

@bp.route("/<make>/<model>"):def return_car(make, model): return jsonify({ "make": make, "model": model})

app.register_blueprint(bp, url_prefix='/car')

Create a Blueprint object

Declare route of the blueprint

Register blueprint

Putting it all together

More Info

http://flask.pocoo.org/

http://flask.pocoo.org/extensions/

http://docs.python-requests.org/en/latest/

https://github.com/marcoslin/flask-restful-into

@marcoseumarcos.lin@farport.co.uk