Flask: for the bold and true

Flask for the bold and true

@dwieeb

Why Flask? • Microframework • Lightweight (~800 lines of code)
• Simple & elegant • Flexible • Extensible ( http://flask.pocoo.org/extensions ) • Doesn’t get in your way

• Django is great! ◦ … if you want to
build an MV* web application with SQL backend ◦ … for monoliths • Django doesn’t make much sense ◦ … if you want to choose your own ORM, Form builder, serializer, etc. ◦ … for single-page apps (AngularJS, React, etc.) ◦ … for SOA & RESTful APIs ◦ … if you like to DIY Why not Django?

WSGI (Web Server Gateway Interface) • PEP 3333 • Python
web interface • Specifies how a Python app should talk to the web

Werkzeug • Python WSGI utility library • Required by Flask

Jinja2 • Python templating language • Fast (with optional ahead-of-time
compilation) • Template inheritance • Blocks • Required by Flask

from flask import Flask app = Flask(__name__) @app.route(‘/’) def hello_world():
return “Hello World!” if __name__ == ‘__main__’: app.run()

@app.route(‘/api/users’, methods=[‘POST’]) def api_create_user(): user = create_user(request.form) return jsonify(user), 201
@app.route(‘/api/users/<int:user_id>’) def api_get_user(user_id): user = get_user(user_id) return jsonify(user)

<!doctype html> <head> <title> {% block title %}{% endblock %}
</title> <link rel="shortcut icon" href="{{ url_for('static', filename='favicon.ico') }}" type="image/x-icon" /> </head> <body> {% block content %}{% endblock %} </body>

{% extends “base.html” %} {% block title %}Welcome Page{% endblock
%} {% block content %} <h1>Welcome</h1> <p>To my website</p> {% endblock %}

Extensions

Flask-SQLAlchemy • Backed by powerful SQLAlchemy ORM • request/response db
sessions • connection pool

Flask-Migrate • Backed by alembic (for SQLAlchemy) • revision autogeneration
• revision branching

Flask-Script • Commander-style script manager • Pythonic option declaration •
Used by Flask-Migrate

Flask-WTF • Backed by WTForms • CSRF stuff • File
uploads

Celery • Distributed task queuing system • Great with RabbitMQ

Flask-Marshmallow • Backed by marshmallow • Serialization/deserialization using schemas defined
in Python • Great for RESTful web services • Model schemas with marshmallow-sqlalchemy

webargs • HTTP request argument parsing ◦ headers ◦ query
parameters ◦ form-data ◦ form-urlencoded ◦ JSON • Requires marshmallow

apispec • Automatically generates Swagger 2.0 API documentation • Requires
marshmallow

Additional resources • Flask Web Development by Miguel Grinberg ◦
github.com/miguelgrinberg/flasky • #pocoo on irc.freenode.net • github.com/humiaozuzu/awesome-flask

Flask: for the bold and true

Flask: for the bold and true

Daniel Imhoff

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