Python Web Framework

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Django?

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Django?

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Django

A high-level Python web framework

Created in 2003, open sourced in 2005

Encourages rapid development and clean, pragmatic design

Widely supported, many deployment options

Focus on automation and DRY

“For perfectionists with deadlines”

MVC (MTV) Architecture

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Who uses Django?

BitBucket

DISQUS (serving 400 million people)

Pinterest

Instagram

dPaste

Mozilla (support.mozill, addons.mozilla)

NASA

PBS (Public Broadcasting Service)

The Washington Post, NY Times, LA Times, The Guardian

National Geographic, Discovery Channel

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Features

Object Relational Mapper - ORM

Template System

customizable Admin Interface, makes CRUD easy

Built-in light weight Web Server

URL design

Authentication / Authorization

Internationalization support

Cache framework, with multiple cache mechanisms

Free, and Great Documentation

MVC vs. MTV

M Model

V View

C Controller

M Model

T Template

V View

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Installation

Prerequisites

Python

PIP for installing Python packages

pip install Django

pip install mysql-python

Testing installation

import django

Create a requirements.txt

$ pip install -r requirements.txt

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Virtualenv

pip “one project, one virtualenv”

projects with different dependencies, package versions

easier to deploy. Forget dependency hell!

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Django Architecture

Models Describes your data

Views Controls what users sees

Templates How user sees it

Controller URL dispatcher

DataBase

Model

View

Template URL dispatcher

Brower

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Project Creation

Creating new Project

django-admin.py startproject demoproject

A project is a collection of applications

Creating new Application

python manage.py startapp demosite

An application tries to provide a single, relatively self-contained set of related functions

Using the built-in web server

python manage.py runserver

Runs by default at port 8000

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Project Directory Structure demosite/

manage.py.

demosite/ __init__.py settings.py

urls.py wsgi.py templates/ static/ demoapp/

__init__.py urls.py views.py models.py admin.py forms.py

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Apps

use short, obvious, single-word names for your apps

many small apps is better than a few giant apps:

explain an app in a sentence. If you can't, split the app

rather than expand an app, write a new app

don't reinvent the wheel!

django.contrib

3rd-party apps

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Settings

use - multiple settings files: - per environment:

dev, testing, staging, production - per developer (local settings)

all settings files must inherit from base, so you can do:

INSTALLED_APPS += ('debug_toolbar', ) - version control all the settings!

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Models

you can use Django without a database

Or

describe your database layout in Python code with django ORM

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Models

from django.db import models

class Reporter(models.Model):

full_name = models.CharField(max_length=70)

def __str__(self): # __unicode__ on Python 2

return self.full_name

class Article(models.Model):

pub_date = models.DateField()

headline = models.CharField(max_length=200)

content = models.TextField() reporter = models.ForeignKey(Reporter)

def __str__(self): # __unicode__ on Python 2

return self.headline

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admin

from django.contrib import admin

from . import models

admin.site.register(models.Article)

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URLs

Map URLs in requests to code that can be executed

Regular expressions!

Subsections of your site can have their own urls.py modules

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URLs

Root URL should be configured in settings.py

o ROOT_URLCONF = 'app.urls'

Example

urlpatterns = patterns(' ',

(r'^articles-year/$', 'mysite.news.views.articles_year'),

)

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Views

Map Code that handles requests

Other frameworks often call these “controllers”

Basically a function that:

gets a request

returns text or a response

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Views

from django.shortcuts import render

from .models import Article

def year_archive(request, year):

a_list = Article.objects.filter(pub_date__year=year)

context = {'year': year, 'article_list': a_list}

return render(request, 'news/year_archive.html', context)

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Django Template Language

Call a function or do logic:

{% ... %}

Variable substitution:

{{ bar }}

Filters:

{{ foo|bar }}

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Django Template Language

{% extends "base.html" %}

{% block title %}Articles for {{ year }}{% endblock %}

{% block content %}

<h1>Articles for {{ year }}</h1>

{% for article in article_list %}

<p>{{ article.headline }}</p>

<p>By {{ article.reporter.full_name }}</p>

<p>Published {{ article.pub_date|date:"F j, Y" }}</p>

{% endfor %}

{% endblock %}

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Django Template Language (base)

{% load staticfiles %}

<html>

<head>

<title>{% block title %}{% endblock %}</title>

</head>

<body>

<img src="{% static "images/sitelogo.png" %}" alt="Logo" />

{% block content %}{% endblock %}

</body>

</html>

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Form

from django import forms

class MyForm(forms.Form):

name = forms.CharField(max_length=30)

email = forms.EmailField()

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Using a Form in a View

from myapp.forms import MyForm

def my_view(request):

form = MyForm(request.POST or None)

if request.method == "POST" and form.is_valid():

name = form.cleaned_data['name']

email = form.cleaned_data['email']

# do something great with that data

return render(request, 'myapp/myform.html', { 'form': form })

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Forms in Templates

<html>

...

<body>

<form action="{% url 'myapp:my_form' %}" method="post">

{% csrf_token %}

{{ form.as_p }}

<button type="submit">Go!</button>

</form>

</body>

</html>

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Django-rest-framework

Django REST framework is a powerful and flexible toolkit for building Web APIs.

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Django-rest-framework (installation)

pip install djangorestframework

pip install django-rest-swagger

Pip install django-filter

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Django-rest-framework (installation) # settings.py INSTALLED_APPS = ( ... ‘rest_framework’, )