how to use validate_comma_separated_integer_list in django

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

• Install Django
• Create Virtual Env

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 models


from django.core.exceptions import ValidationError

def 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 forms
from .models import Product

class 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 render
from .models import Productfrom django.shortcuts import render
from django.http import HttpResponse
from django.shortcuts import redirect, render
from django.db import models


def 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, redirect
from .forms import ProductForm

def 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 path
from . import views

urlpatterns = [
    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 admin
from django.urls import path, include

urlpatterns = [
    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