Django cheat sheet

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_nameMigration: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 makemigrationsMigrate: Will read the migrations files and create the actual database and tables~$ python manage.py migrateCreate superuser for authenficiation/admin panel~$ python manage.py createsuperuserStart server~$ python manage.py runserver => ex. http://127.0.0.1:8000Requirements# 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.txtOther 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 jsonpython manage.py dumpdata blog >myapp.json# Take all data in json file and import in app data tablepython manage.py loaddata myapp.jsonProject config# Add app to settings.pyINSTALLED_APPS = [ … , 'app_name' ]# App templates foldercreate folder appfolder/templates/appname# Project templates folder: create folder projectname/templates# settings.py template configProject 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.pyDATABASE = { '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 belowfrom django.db import modelsclass 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 representationclass Customer(models.Model): name = models.Charfield('Customer', max_length=120) age = models.IntegerField() def __str__(self): return self.nameRelationship 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 methoddef 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 filefrom .models import Blogadmin.site.register(Blog)Customize Admin PanelFor 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 appadmin.site.register(Blog, BlogAdmin)Routing:Django routing info is store in project_folder/urls.py filefrom django.contrib import adminfrom django.urls import path, includeurlpatterns = [ 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 pathfrom . import viewsurl 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 routefrom django.conf import settingsfrom django.conf.urls.static import staticurlpatterns += static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)Function Based Views# views.pyfrom django.shortcuts import render, redirectfrom .models import Postfrom .forms import PostFormdef 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 Viewsfrom django.views.generic import TemplateView, ListView, DetailView, CreateView, UpdateView, DeleteViewclass 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 contextclass 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 contextclass PostsDeleteView(DeleteView): model = Post template_name = 'posts/post_delete.html' success_url = reverse_lazy('posts-list')# Urls.py route declarationpath('<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 saveArticle.objects.create(name='Item 1', price=19.95) # Read allArticle.objects.all()# Createuser = User.objects.first()article = Article(user=user, name='Item 1', price=19.95)# Savearticle.save()# Read oneArticle.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 pagefrom django.shortcuts import get_object_or_404article = 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 fieldArticle.objects.get(user__username='mike')# Ordering Article.objects.order_by('name') # ascendingArticle.objects.order_by('-name') # descending# Slicing return firstArticle.objects.all().order_by('name')[0]# Slicing return lastArticle.objects.all().order_by('-name')[0]# Slicing limit/offsetArticle.objects.all().order_by('name')[1..10]# Updatingarticle = Article.objects.first()article.name = 'new name'article.save()# One line updateArticle.objects.filter(id=4).update(name='new name')# Deletingarticle = Article.objects.first()article.delete()# One line deletearticle.objects.get(id=1).delete()# Delete allArticle.objects.all().delete()# Set ForeignKey field valuemodel1 = Model(name='dyson')article.model = model1# Get ForeignKey valuearticle1.model.namemodel1.article_set.all()# Add Many-to-Manyarticle1.tags.add(tag1) article1.tags.all()tag1.articles_set.all()Form (forms.py)from django import formsclass ArticleForm(forms.Form): name = forms.Charfield(max_length=100) description = forms.Charfield(blank=True, null = True)# Model Form from django.forms import ModelFormfrom .models import Articleclass 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-tailwindpip install crispy-tailwind# settings.pyCRISPY_ALLOWED_TEMPLATE_PACKS = 'tailwind'CRISPY_TEMPLATE_PACK = 'tailwind'# template usage{% load tailwind_filters %}{{ form|crispy}}Form validation# forms.pyfrom 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 messagesmessages.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 modelfrom django.contrib.auth import get_user_modelUser = get_user_model()# Or if you want to custom user modelfrom django.contrib.auth.models import AbstractUserclass 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 Djangofrom django.contrib.auth.views import LoginView# Add a url to reach that viewpath('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.pyAuthentification: LogoutView# LogoutView is already pre-created by Djangofrom django.contrib.auth.views import LogoutView# Add a url to reach that viewpath('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.pyAuthentification: SignupView# Create a SignupView (that view is not created by default)# import sinupview form pre-created by Djangofrom django.contrib.auth.forms import UserCreationFormfrom django.views.generic import CreateViewclass 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 viewfrom posts.views import SignupViewpath('signup/', SignupView.as_view(), name='signup')# Optional: Customize the UserCreationForm# (forms.py)from django.contrib.auth import get_user_modelfrom django.contrib.auth.forms import UserCreationFormUser = get_user_model()class CustomUserCreationForm(UserCreattionForm): class Meta: model = User fields = ['username'] fields_classes = {'username': UsernameField}Optional pre-created authentification routes# urls.pyurlpatterns += 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_requiredfrom 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 Logoutfrom django.contrib.auth import authenticate, logindef 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 passworduser.set_password('raw password')Send Email# settings.pyEMAIL_BACKEND = "django.core.mail.backends.console.EmailBackend"# Send email functionfrom django.core.email import send_mailsend_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.pyfrom django.db.models.signals import post_save, pre_savedef 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 savepost_save.connect(post_user_created_signal, sender=User)Seedfrom .models import Product, Categoryfrom django.shortcuts import HttpResponsefrom faker import Fakerdef 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-dotenvadd code to manage.py fileimport dotenvdef main(): """Run administrative tasks.""" dotenv.read_dotenv() #add this line ... ...Create a file name '.env' in the root folder of your projectSECRET_KEY = 'your secret key'ALLOWED_HOST=127.0.0.1In settings.py change security related settings to point to the .env fileimport osSECRET_KEY = os.environ.get('SECRET_KEY')ALLOWED_HOSTS = os.environ.get('ALLOWED_HOSTS')