Eric The Coder
Eric The Coder Blog

Eric The Coder Blog

Ultimate Django Sheet Cheat

Ultimate Django Sheet Cheat

Eric The Coder's photo
Eric The Coder

Published on Sep 22, 2021

11 min read

Django memory aid : Everything you need to remember to create a Python Django Web Application

Follow me!:


Start a new Django project

# Create et access project folder
~$  mkdir project_name
~$  cd project_name

# Create Python virtual env 
~$  python3 -m venv venv

# Activate virtual env
~$  source venv/bin/activate

# If you want to deactivate virtual env
~$  deactivate

# Install django (~= same as 3.1.*)
~$  pip install django~=3.1.0 

# New django project (from project_name folder)
~$  django-admin startproject config .

# Create app (from project_name folder)
~$  python manage.py startapp app_name

Migration: Django create a database table for each models present in your app using thoses commands:

  • Makemigrations: Create a file under app_name/migrations with the database structure to create
    ~$  python manage.py makemigrations
    
  • Migrate: Will read the migrations files and create the actual database and tables
    ~$  python manage.py migrate
    

Create superuser for authenficiation/admin panel

~$  python manage.py createsuperuser

Start server

~$  python manage.py runserver  => ex.  http://127.0.0.1:8000

Requirements

# Create a requirements file that contain all your projet dependencies
~$  pip freeze > requirements.txt

# Install your project requirements (if a requirements file exist) 
~$  pip install -r requirements.txt

Other commands

# Django shell (Run projet code direclty)
~$ python manage.py shell

# example of code to run in the shell:
 >>> from app_name.models import User
 >>> user1 = User.objects.first()

# Prepare static folders for production
$ python manage.py collectstatic

# Take all data from app blog and export in json
python manage.py dumpdata blog >myapp.json

# Take all data in json file and import in app data table
python manage.py loaddata myapp.json

Project config

# Add app to settings.py
INSTALLED_APPS = [ … , 'app_name' ]

# App templates folder
create folder appfolder/templates/appname

# Project templates folder: 
create folder projectname/templates

# settings.py template config
Project templates settings.py: 
    TEMPLATES = [
        { …
                'DIRS': [BASE_DIR / 'templates', ],
        … }

# Create Static folder: 
project_name\static\

# Static folder (settings.py): 
STATIC_URL = '/static/'
STATICFILES_DIRS = [ BASE_DIR / 'static' ] 
STATIC_ROOT = 'static_root'

# To use PostgresSQL
# pip install psycopg2
# settings.py
DATABASE = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'blog',
        'USER': 'admin',
        'PASSWORD': '123456',
        'HOST': 'localhost',
        'PORT': '5432'

Create data model: Theses models can be created as database tables with the migrations commands

# models.py
# The id fields is automaticly created by Django for each model that why it's not show below

from django.db import models

class Customer(models.Model)
    name = models.Charfield('Customer', max_length=120)
    age = models.IntegerField()
    note = models.TextField(blank=True, null = True)
    email = models.EmailField(max_length=255, blank=True, null=True)
    credit = models.FloatField(blank=True)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    # Select Field (return value, display value)
    TYPE_CHOICES = (
        ('Customer', 'Customer'),
        ('Supplier', 'Supplier'),
        ('Student', 'Student'),
    )

    type = models.CharField(choices=TYPE_CHOICES)

Model string representation

class Customer(models.Model):
    name = models.Charfield('Customer', max_length=120)
    age = models.IntegerField()

    def __str__(self): 
        return self.name

Relationship between models

# One-to-Many: (use double quotes if the entity is not yet declare) ex. "Supplier"
supplier = models.ForeignKey(Supplier, blank=True, null=True, on_delete=models.CASCADE)

# on_delete can be set to models.CASCADE, models.ST_DEFAULT or models.SET_NULL

# Many-to-Many: 
tags = models.ManyToManyField(Tag, blank=True)

# One to One 
User = models.OneToOneField(User, on_delete=models.CASCADE)

# Overwrite save method
def save(self, (*args, **kwargs):
    if not self.slug:
        self.slug = slugify(self.title)

    super().save(*args, **kwargs)

Admin panel: Every Django projects come with an Admin Panel that can be open at /admin url (ex: localhost:8000/admin)

To display the model in the Admin panel register the model in the app_name/admin.py file

from .models import Blog
admin.site.register(Blog)

Customize Admin Panel

For each models you can specify the fields you want to use

# Custom model Admin (admin.py): 
class BlogAdmin(admin.ModelAdmin)
    fields = ("title", "description") # Fields to use for add/edit/show page
    list_display = ("title", "description") # fields to display in search page
    list_display_links = ("title") # fields that will be a link in search page
    ordering("date_created",) # Ordering allowed in the search page
    search_fields("title", "description") # Search fields allowed in the search page

# Register app
admin.site.register(Blog, BlogAdmin)

Routing: Django routing info is store in project_folder/urls.py file

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

urlpatterns = [
    path('admin/', admin.site.urls), # pre-created admin urls routes
    path('', include('app_name.urls')) # include your app urls
]

the 'include()' method allow to link another urls.py file created in your app folder (app_name/urls.py)

from django.urls import path
from . import views

url patterns = [ 
    path('posts', views.index, name='posts.index'),
    path('posts/create/', views.create, name='posts.create',
    path('posts/<int:id>/', views.show, name='posts.show'),
    path('posts/<int:id>/edit/', views.edit, name='posts.edit'),
    path('posts/<int:id>/delete/', views.delete, name='posts.delete'),
]

Static route

from django.conf import settings
from django.conf.urls.static import static

urlpatterns += static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)

Function Based Views

# views.py
from django.shortcuts import render, redirect
from .models import Post
from .forms import PostForm

def index(request):
    # Get all Posts
    posts = Post.objects.all()

    # Render app template with context
    return render(request, 'appfolder/index.html', {'posts': posts})

def show(request, id):
    post = Post.objects.get(id=id)
    return render(request, 'appfolder/show.html', {'post': post})

def create(request):
    form = PostForm(request.POST or None)
    if form.is_valid():
        # optionally we can access form data with form.cleaned_data['first_name']
        post = form.save(commit=False)
        post.user = request.user
        post.save()
        return redirect('/posts')

    return render(request, 'appfolder/create.html', {'form': form)

def edit(request, id):
    post = Post.objects.get(id=id)
    form = PostForm(request.POST or None, instance=post)
    if form.is_valid():
        form.save()
        return redirect('/posts')

    return render(request, 'appfolder/edit.html', {'form': form)

def delete(request, id):
    post = Post.objects.get(id=id)
    post.delete()
    return redirect('/posts')

Class based Views

from django.views.generic import TemplateView, ListView, DetailView, CreateView, UpdateView, DeleteView

class LandingPageView(TemplateView):
    template_name = 'landing.html'

    # Optional: Change context data dict
    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['title'] = 'Landing Page'
        return context

class PostsListView(ListView):
    queryset = Post.objects.all()

  # Optional
    # context_object_name = "posts" (default: post_list)
    # template_name = 'posts.html' (default: posts/post_list.html) 

class PostsDetailView(DetailView):
    model = Post # object var in template

  # Optional
    # template_name = 'post.html' (default: posts/post_detail.html)


class PostsCreateView(CreateView):
    form_class = PostForm

    template_name = 'posts/post_create.html' # no default value

    def get_success_url(self):
        return reverse('posts-list')

    # Optional: Overwrite form data (before save)
    def form_valid(self, form):
        if self.request.user.is_authenticated:
            from.instance.author = self.request.user

        return super().form_valid(form)

class PostsUpdateView(UpdateView):
    model = Post
    form_class = PostForm
    template_name = 'posts/post_update.html'

    def get_success_url(self):
        return reverse('post-list')

    # Optional: Change context data dict
    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['submit_text'] = 'Update'
        return context


class PostsDeleteView(DeleteView):
    model = Post
    template_name = 'posts/post_delete.html'
    success_url = reverse_lazy('posts-list')

# Urls.py route declaration
path('<int:pk>/update/', PostsUpdateView.as_view(), name='post-update')

Django Template: Templates are store in project_folder/templates or in your app_folder/templates/app_name/*.html

{% extends 'base.html' %}
{% block content %}     
{% endblock %} 

{% include 'header.html' %} 

{% if user.username = 'Mike' %}
    <p>Hello Admin</p>   
{% else %}   
    <p>Hello User</p>
{% endif %} 

{% for product in products %}   
  <p>The product name is {{ product }}<p>
{% endfor %} 

{{ var_name }}

Template variables formating
{{ title | lower }} 
{{ blog.post | truncatwords:50 }}
{{ order.date | date:"D M Y" }}
{{ list_items | slice:":3" }}
{{ total | default:"nil" }}

Current path (ex. posts/1/show)
{{ request.path }}   

URL by name with param
{% url 'posts.delete' id=post.id %}

Use static in template: 
{% load static %}
{% static 'css/main.css' %}

Model Managers and Querysets: Model manager allow model database reads and writes

# One line create and save
Article.objects.create(name='Item 1', price=19.95) 

# Read all
Article.objects.all()

# Create
user = User.objects.first()
article = Article(user=user, name='Item 1', price=19.95)

# Save
article.save()

# Read one
Article.objects.get(id=1) 

# Select Related (to avoid n+1 query)
posts = Post.objects.select_related('user', 'category').all()

# Read or render a 404 not found page
from django.shortcuts import get_object_or_404
article = get_object_or_404(Article, id=512)

# Filter 
Article.objects.filter(model='dyson', name__icontains='dyson') # __icontains    
Article.objects.filter(year__gt=2016) # __gt = greater than 
Article.objects.filter(year__lt=2001) # __lt = less than 

# Filter on relationship sub model field
Article.objects.get(user__username='mike')

# Ordering 
Article.objects.order_by('name')     # ascending
Article.objects.order_by('-name')   # descending

# Slicing return first
Article.objects.all().order_by('name')[0]

# Slicing return last
Article.objects.all().order_by('-name')[0]

# Slicing limit/offset
Article.objects.all().order_by('name')[1..10]

# Updating
article = Article.objects.first()
article.name = 'new name'
article.save()

# One line update
Article.objects.filter(id=4).update(name='new name')

# Deleting
article = Article.objects.first()
article.delete()

# One line delete
article.objects.get(id=1).delete()

# Delete all
Article.objects.all().delete()

# Set ForeignKey field value
model1 = Model(name='dyson')
article.model = model1

# Get ForeignKey value
article1.model.name
model1.article_set.all()

# Add Many-to-Many
article1.tags.add(tag1) 
article1.tags.all()
tag1.articles_set.all()

Form (forms.py)

from django import forms
class ArticleForm(forms.Form): 
    name = forms.Charfield(max_length=100)
    description = forms.Charfield(blank=True, null = True)


# Model Form 
from django.forms import ModelForm
from .models import Article
class ArticleForm(ModelForm):
    class Meta:
        model = Article
        fields = ['name', 'description', 'price'] # Use '__all__' for all fields


# Render form in template
<form method=“post” action=“” novalidate> 
    {% csrf_token %}
    {{ form }} 
    <button type="submit">Submit</button>
</form>

# Bootstrap (pip install django-crispy-forms + installed_apps: 'crispy_forms')
{% load crispy_forms_tags %}
{{ form|crispy }}
{{ form.email|as_crispy_field }}

# crispy-tailwind
pip install crispy-tailwind

# settings.py
CRISPY_ALLOWED_TEMPLATE_PACKS = 'tailwind'
CRISPY_TEMPLATE_PACK = 'tailwind'

# template usage
{% load tailwind_filters %}
{{ form|crispy}}

Form validation

# forms.py
from django.core.exceptions import ValidationError

# field validation 
def clean_first_name(self):
    data = self.cleaned_data['first_name']
    if data = 'Mike':
        raise ValidationError('Your name must not be Mike')

    return data

# form validation 
def clean(self):
    first_name = self.cleaned_data['first_name']
    last_name = self.cleaned_data['last_name']
    if first_name + last_name = 'MikeTaylor':
        raise ValidationError('Your name must not be Mike Taylor')

Flash messages

messages.success(request, 'Login successful')
messages.error(request, 'Login error')

# Message tags
# debug, info, success, warning and error

# Display flash in template 
{% if messages %} 
    {% for message in messages %} 
        {% message %} 
        {% message.tags %}

User model (pre-created)

# Get a reference to Django pre-created User model
from django.contrib.auth import get_user_model

User = get_user_model()

# Or if you want to custom user model
from django.contrib.auth.models import AbstractUser

class User(AbstractUser): 
    # add custom fields and methods

# To make Django use that model go to settings.py and add: AUTH_USER_MODEL = 'app_name.User'

Authentification: LoginView

# LoginView is already pre-created by Django
from django.contrib.auth.views import LoginView

# Add a url to reach that view
path('login/', LoginView.as_view(), name='login')

# By default the LoginView will try to open a template name 'registration/login.html' and send a login form with it.

# Create a template under registration/login.html
{% extends "base.html" %}
{% block content %}
    <form method="post">
        {% csrf_token %}
        {{ form }}
        <button type="submit">Login</button>
    </form>
{% endblock content %}

# When user click the Login button, the LoginView will try to authenticate the user with the form username ans password. 

# If successful il will then login the user and redirect to LOGIN_REDIRECT_URL specified in your settings.py

Authentification: LogoutView

# LogoutView is already pre-created by Django
from django.contrib.auth.views import LogoutView

# Add a url to reach that view
path('logout/', LoginView.as_view(), name='logout')

# Include a link in a template
<a> href="{% url 'logout' %}">Logout</a>

# After link is execute, the user will be logout and redirect to LOGOUT_REDIRECT_URL specified in your settings.py

Authentification: SignupView

# Create a SignupView (that view is not created by default)
# import sinupview form pre-created by Django
from django.contrib.auth.forms import UserCreationForm
from django.views.generic import CreateView

class SignupView(CreateView):
    template_name = 'registration/signup.html'
    form_class = UserCreationForm

    def get_success_url(self):
        return reverse("login")


# Create template: registration/signup.html
{% extends "base.html" %}
{% block content %}
    <form method="post">
        {% csrf_token %}
        {{ form }}
        <button type="submit">Signup</button>
    </form>
{% endblock content %}

# Add a url to reach that view
from posts.views import SignupView

path('signup/', SignupView.as_view(), name='signup')

# Optional: Customize the UserCreationForm
# (forms.py)
from django.contrib.auth import get_user_model
from django.contrib.auth.forms import UserCreationForm

User = get_user_model()
class CustomUserCreationForm(UserCreattionForm):
    class Meta:
        model = User
        fields = ['username']
        fields_classes = {'username': UsernameField}

Optional pre-created authentification routes

# urls.py
urlpatterns += path('', include('django.contrib.auth.urls'))
# /login, /lougout, /signup, etc.

Template Authentification helpers

# Authentication links
<a href="{% url 'login' %}">Login</a>
<a href="{% url 'signup' %}">Signup</a>
<a href="{% url 'logout' %}">Logout</a>

# Check if user login
{% if request.user.is_authenticated %}
    Logged in as: {{ request.user.username }}
{% endif %}

Authorization: LoginRequiredMixin and login_required

from django.contrib.auth.mixins import LoginRequiredMixin

# Restrict views to auth user only (views.py)
class PostsCreateView(LoginRequiredMixin, generic.CreateView):
    ...
    ...


from django.contrib.auth.decorators import login_required

@login_required(login_url='/login')
def search_page(request):
    ...
    ...

Manual Authentification, Login and Logout

from django.contrib.auth import authenticate, login

def login_page(request):
    if request.method == "POST":
        username = request.POST.get("username")
        password = request.POST.get("password")
        user = authenticate(request, username=username, password=password)
        if user is not None:
            login(request, user)
            return redirect("index")

return render(request, "registration/login.html", {})


def logout_page(request):
    logout(request)
    return redirect("index")

User Change password

# set_password will hash the password
user.set_password('raw password')

Send Email

# settings.py
EMAIL_BACKEND = "django.core.mail.backends.console.EmailBackend"

# Send email function
from django.core.email import send_mail

send_mail(
    subject = "A new post has been created",
    messsage = "Go to the web site to see the detail",
    from_email = "test@test.com",
    recipient_list = ["test2@text.com"]
)

Signals

# models.py
from django.db.models.signals import post_save, pre_save

def post_user_created_signal(sender, instance, created, **kwargs):
    if created:
        UserProfile.objects.create(user=instance)


# Launch the post_user_create_singal method if User model is save
post_save.connect(post_user_created_signal, sender=User)

Seed

from .models import Product, Category
from django.shortcuts import HttpResponse
from faker import Faker


def seed(request):
    Product.objects.all().delete()
    Category.objects.all().delete()

    category = Category()
    category.name = "Sports"
    category.save()

    category = Category()
    category.name = "Home"
    category.save()

    fake = Faker()
    for _ in range(100):
        product = Product()
        product.name = fake.unique.word()
        product.short_description = fake.sentence()
        product.main_picture = fake.image_url()
        product.price = fake.random_digit() * 10
        product.category =  Category.objects.order_by('?').first()
        product.save()

    return HttpResponse('Seeded')

.env key/value file

$ pip install django-dotenv

add code to manage.py file

import dotenv

def main():
    """Run administrative tasks."""
    dotenv.read_dotenv() #add this line
    ...
    ...

Create a file name '.env' in the root folder of your project

SECRET_KEY = 'your secret key'
ALLOWED_HOST=127.0.0.1

In settings.py change security related settings to point to the .env file

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

Did you find this article valuable?

Support Eric The Coder by becoming a sponsor. Any amount is appreciated!

Learn more about Hashnode Sponsors
 
Share this