A validator is a callable that takes a value and raises a ValidationError if it doesn’t meet the criteria. Validators can be useful for re-using validation logic between different types of fields. In this article, we will learn how to use ‘validate_comma_separated_integer_list’ validator in Django.
Required modules
Use of validate_comma_separated_integer_list in Django
To start the project please use these commands
django-admin startproject queryexpressionsproject
cd app
To start the app use this command
python manage.py startapp app
Now add this app to the ‘settings.py’
Setting up the Files
model.py: This code defines a Django model for products with fields for name, price, quantity, and categories. It also includes a custom validator to ensure that the categories field contains a comma-separated list of valid integers. If any of the integers are not valid, a validation error is raised.
Python3
from django.db import modelsfrom django.core.exceptions import ValidationErrordef validate_comma_separated_integer_list(value): """ Validate that a value is a comma-separated list of integers. """ values = value.split(',') for val in values: try: int(val) except ValueError: raise ValidationError("One or more items in the list are not valid integers.")class Product(models.Model): name = models.CharField(max_length=100) price = models.DecimalField(max_digits=10, decimal_places=2) quantity = models.PositiveIntegerField() categories = models.CharField(max_length=200, validators=[validate_comma_separated_integer_list]) def __str__(self): return self.name |
form.py: In the products/forms.py file, create a new form class or update an existing one. This form is used to collect data from the user.
Python3
from django import formsfrom .models import Productclass ProductForm(forms.ModelForm): class Meta: model = Product fields = ['name', 'price', 'quantity', 'categories'] |
views.py: Below is the working of each function:
- This home function defines a simple view called home. When a user visits the homepage of the application, it returns an HTTP response with the text “Hello World!”.
- This function defines a view called expensive_products. When a user visits this page, it calculates the total value of products by multiplying the “price” and “quantity” fields and filters for products with a total value greater than $1000 using Django query expressions. It then renders the index.html template, passing the expensive_products queryset to be displayed in the template.
- This function defines a view called create_product for creating a new product. When a user submits a form with a POST request, it validates the form data using a ProductForm. If the form is valid, it saves the product to the database and redirects the user to the expensive_products view. If it’s not a POST request, it renders the index2.html template with the ProductForm to allow the user to create a new product.
Python3
from django.shortcuts import renderfrom .models import Productfrom django.shortcuts import renderfrom django.http import HttpResponsefrom django.shortcuts import redirect, renderfrom django.db import modelsdef home(request): return HttpResponse('Hello World!')def expensive_products(request): # Calculate the total value and filter for expensive products expensive_products = Product.objects.annotate( total_value=models.ExpressionWrapper( models.F('price') * models.F('quantity'), output_field=models.DecimalField()) ).filter(total_value__gt=1000) return render(request, 'myapp/index.html', {'expensive_products': expensive_products})from django.shortcuts import render, redirectfrom .forms import ProductFormdef create_product(request): if request.method == 'POST': form = ProductForm(request.POST) if form.is_valid(): form.save() return redirect('expensive_products') # Redirect to the expensive products page or another appropriate page else: form = ProductForm() return render(request, 'myapp/index2.html', {'form': form}) |
index.html: The index.html template to display the categories for each product.
HTML
<!DOCTYPE html><html><head> <title>Expensive Products</title></head><body> <h1>Expensive Products</h1> <ul> {% for product in expensive_products %} <li> <strong>{{ product.name }}</strong><br> Price: ${{ product.price }}<br> Quantity: {{ product.quantity }}<br> Categories: {{ product.categories }}<br> Total Value: ${{ product.total_value }} </li> {% endfor %} </ul></body></html> |
index2.html: This template renders the product creation form.
HTML
<!DOCTYPE html><html><head> <title>Create Product</title></head><body> <h1>Create Product</h1> <form method="post"> {% csrf_token %} {{ form.as_p }} <button type="submit">Create</button> </form></body></html> |
urls.py: In products/urls.py to include a new URL pattern for the product creation view.
Python3
from django.urls import pathfrom . import viewsurlpatterns = [ path('hello/', views.home, name='home'), path('expensive-products/', views.expensive_products, name='expensive_products'), path('create-product/', views.create_product, name='create_product'),] |
urls.py: Include the ‘products’ app’s URLs in the project’s main urls.py file.
Python3
from django.contrib import adminfrom django.urls import path, includeurlpatterns = [ path('admin/', admin.site.urls), path('', include('app.urls')),] |
Deployement of the project
Run these commands to apply the migrations:
python3 manage.py makemigrations
python3 manage.py migrate
Run the server with the help of following command:
python3 manage.py runserver
Output
