📜 Django Cheat Sheet

A cheat-sheet for creating web apps with the Django framework using the Python language. Most of the summaries and examples are based on the official documentation for Django v2.0.

Sections

🐍 Initializing pipenv (optional)
📘 Creating a project
📃 Creating an app
📺 Creating a view
🎨 Creating a template
🎫 Creating a model
📮 Creating model objects and queries
👨 Using the Admin page

🐍 Initializing pipenv (optional)

Make main folder with $ mkdir <folder> and navigate to it with $ cd <folder>
Initialize pipenv with $ pipenv install
Enter pipenv shell with $ pipenv shell
Install django with $ pipenv install django
Install other package dependencies with $ pipenv install <package_name>

📘 Creating a project

Navigate to main folder with $ cd <folder>
Create project with $ django-admin startproject <project_name>

The project directory should look like this:

project/
    manage.py
    project/
        __init__.py
        settings.py
        urls.py
        wsgi.py

Run the development server with $ python manage.py runserver within the project directory
If you want your SECRET_KEY to be more secure, you can set it to reference an environment variable
In the settings.py file within the project directory change the SECRET_KEY line to the following:

SECRET_KEY = os.environ.get('SECRET_KEY')

To quickly generate a random hex for your secret key:

>>> import secrets
>>> secrets.token_hex()

You can set this environment variable in your shell with export SECRET_KEY=<secret_key>

📃 Creating an app

Navigate to the outer project folder $ cd <outer_project_folder>
Create app with $ python manage.py startapp <app_name>
Inside the app folder, create a file called urls.py

The project directory should now look like this:

project/
    manage.py
    db.sqlite3
    project/
        __init__.py
        settings.py
        urls.py
        wsgi.py
    app/
        migrations/
            __init__.py
        __init__.py
        admin.py
        apps.py
        models.py
        tests.py
        urls.py
        views.py

To include this app in your project, add your app to the project's settings.py file by adding its name to the INSTALLED_APPS list:

INSTALLED_APPS = [
	'app',
	# ...
]

To migrate changes over:

$ python manage.py migrate

📺 Creating a view

Within the app directory, open views.py and add the following:

from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello, World!")

Still within the app directory, open (or create) urls.py

from django.urls import path
from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

Now within the project directory, edit urls.py to include the following

from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('app/', include('app.urls')),
    path('admin/', admin.site.urls),
]

To create a url pattern to the index of the site, use the following urlpattern:

urlpatterns = [
    path("", include('app.urls')),
]

Remember: there are multiple files named urls.py
The urls.py file within app directories are organized by the urls.py found in the project folder.

🎨 Creating a template

Within the app directory, HTML, CSS, and JavaScript files are located within the following locations:

app/
   templates/
      index.html
   static/
      style.css
      script.js

To add a template to views, open views.py within the app directory and include the following:

from django.shortcuts import render

def index(request):
    return render(request,'index.html')

To include context to the template:

def index(request):
	context = {"context_variable": context_variable}
    return render(request,'index.html', context)

Within the HTML file, you can reference static files by adding the following:

{% load static %}

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8">
		<meta name="viewport" content="width=device-width, initial-scale=1">
		
		<link rel="stylesheet" href="{% static 'styles.css' %}">
	</head>
</html>

To make sure to include the following in your settings,py:

STATIC_URL = '/static/'
STATICFILES_DIRS = [
	os.path.join(BASE_DIR, "static")
]

To add an extends:

{% extends 'base.html'%}

{% block content %}

Hello, World!

{% endblock %}

And then in base.html add:

<body>
	{% block content %}{% endblock %}
</body>

🎫 Creating a model

Within the app's models.py file, an example of a simple model can be added with the following:

from django.db import models

class Person(models.Model):
	first_name = models.CharField(max_length=30)
	last_name = models.CharField(max_length=30)

Note that you don't need to create a primary key, Django automatically adds an IntegerField.

To perform changes in your models, use the following commands in your shell:

$ python manage.py makemigrations <app_name>
$ python manage.py migrate

Note: including <app_name> is optional.

A one-to-many relationship can be made with a ForeignKey:

class Musician(models.Model):
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    instrument = models.CharField(max_length=100)

class Album(models.Model):
    artist = models.ForeignKey(Musician, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)
    release_date = models.DateField()
    num_stars = models.IntegerField()

In this example, to query for the set of albums of a musician:

>>> m = Musician.objects.get(pk=1)
>>> a = m.album_set.get()

A many-to-many relationship can be made with a ManyToManyField:

class Topping(models.Model):
    # ...
    pass

class Pizza(models.Model):
    # ...
    toppings = models.ManyToManyField(Topping)

Note that the ManyToManyField is only defined in one model. It doesn't matter which model has the field, but if in doubt, it should be in the model that will be interacted with in a form.

Although Django provides a OneToOneField relation, a one-to-one relationship can also be defined by adding the kwarg of unique = True to a model's ForeignKey:

ForeignKey(SomeModel, unique=True)

For more detail, the official documentation for database models provides a lot of useful information and examples.

📮 Creating model objects and queries

Example models.py file:

from django.db import models

class Blog(models.Model):
    name = models.CharField(max_length=100)
    tagline = models.TextField()

    def __str__(self):
        return self.name

class Author(models.Model):
    name = models.CharField(max_length=200)
    email = models.EmailField()

    def __str__(self):
        return self.name

class Entry(models.Model):
    blog = models.ForeignKey(Blog, on_delete=models.CASCADE)
    headline = models.CharField(max_length=255)
    body_text = models.TextField()
    pub_date = models.DateField()
    mod_date = models.DateField()
    authors = models.ManyToManyField(Author)
    n_comments = models.IntegerField()
    n_pingbacks = models.IntegerField()
    rating = models.IntegerField()

    def __str__(self):
        return self.headline

To create an object within the shell:

$ python manage.py shell

>>> from blog.models import Blog
>>> b = Blog(name='Beatles Blog', tagline='All the latest Beatles news.')
>>> b.save()

To save a change in an object:

>>> b.name = 'The Best Beatles Blog'
>>> b.save()

To retrieve objects:

>>> all_entries = Entry.objects.all()
>>> indexed_entry = Entry.objects.get(pk=1)
>>> find_entry = Entry.objects.filter(name='Beatles Blog')

👨 Using the Admin page

To create a superuser:

$ python manage.py createsuperuser

To add a model to the Admin page include the following in admin.py:

from django.contrib import admin
from .models import Author, Book

admin.site.register(Author)
admin.site.register(Book)

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