Installation

$ pip install Flask

Hello World

# myapp.py
from flask import Flask
app = Flask(__name__)

@app.route(‘/’)
def hello_world():
    return ‘Hello World’
if __name__ == ‘__main__’:
    app.run(debug=True)

For Heroku

# in production Heroku will set the PORT environment variable.

if __name__ == '__main__':
    # Bind to PORT if defined, otherwise default to 5000.
    port = int(os.environ.get('PORT', 5000))
    app.run(host='0.0.0.0', port=port, debug=True)

URL Routing

@app.route(‘/foo/<name>/<int:age>’)
def view(name, age):
    return ‘%s is %d years old’ % (
        name, age
    )

Template Rendering

from flask import render_template

return render_template(
    ‘foo.html’,
    var1=value1, var2=value2, ...
    )

Flask for Django users

Action Django Flask
Retrieve query params (“GET data”) request.GET request.GET[‘name’] request.args request.args[‘name’]
Retrieve form params (“POST data”) request.POST request.POST[‘first_name’] request.form request.form[‘name’]
Checking request type request.method request.method
Retrieve cookie value request.COOKIES request.cookies
Set a cookie response.set_cookie(key, value, …) response.set_cookie(key, value, …)
Sessions request.session[‘foo’] session[‘foo’]
Access settings from django.conf import settings settings.my_name app.config app.config[‘my_name’]

Useful functionality

From flask import.. This is a… usage
Flask Flask application object app = Flask(name)
request Thread-local request object request.args[‘test’] request.form[‘name’]
session Thread-local session object session[‘name’] = ‘value’
url_for Builds URLs based on route names url_for(‘blog’, id=45, slug=‘hi’)
redirect Generates a redirect response return redirect(‘/hello’)

Basic App Layout

Commands:

mkdir templates
mkdir static

touch templates/index.html
touch static/base.css
touch my_app.py

Structure:

my_app.py
static/
    logo.png
    base.css
templates/
    blog_post.html
    index.html

Package App Layout

Commands:

mkdir ~/my_app
mkdir ~/my_app/templates
mkdir ~/my_app/static  

cd my_app
touch __init__.py
touch application.py
touch models.py
touch static/base.css
touch templates/index.html

Structure:

my_app/
    __init__.py
    application.py
    models.py
    static/
        logo.png
        base.css
    templates/
        blog_post.html
        index.html

Large applications structure

Link

Commands:

mkdir ~/LargeApp
mkdir ~/LargeApp/app
mkdir ~/LargeApp/app/templates
mkdir ~/LargeApp/app/static  

cd ~/LargeApp
virtualenv env
touch ~/LargeApp/run.py
touch ~/LargeApp/config.py
touch ~/LargeApp/app/__init__.py

Structure:

~/LargeApp
    |-- run.py
    |-- config.py
    |__ /env             # Virtual Environment
    |__ /app             # Our Application Module
         |-- __init__.py
         |-- /module_one
             |-- __init__.py
             |-- controllers.py
             |-- models.py                
         |__ /templates
             |__ /module_one
                 |-- hello.html
         |__ /static
         |__ ..
         |__ .
    |__ ..
    |__ .

More Info