Django·Django from project to API

Forms and validation

Build forms from models, validate input and render accessible errors.

Intermediate 14 min read Lesson 6 of 300 Challenge included

What you will be able to do

Use forms.Form for custom input and ModelForm for models.
Always include {% csrf_token %}.
Render field errors next to the field.
Call form.is_valid() before saving.

In plain English

Django forms handle rendering, binding and validation. A ModelForm derives fields from a model. Validation lives in the form, so the same rules apply whether the request comes from a browser or an API.

forms.pyPython

from django import forms
from .models import Lesson

class LessonForm(forms.ModelForm):
    class Meta:
        model = Lesson
        fields = ('title', 'minutes', 'published')

    def clean_minutes(self) -> int:
        minutes = self.cleaned_data['minutes']
        if minutes < 1 or minutes > 240:
            raise forms.ValidationError('Minutes must be between 1 and 240.')
        return minutes

Your turn

Add a slug field

Easy

Add a slug ModelForm field for Lesson.

PYTHON · starter

fields = ('title', 'minutes')

Check your understanding before moving on.

Knowledge checkQuestion 1

Which template tag adds CSRF protection to a form?

Select an answer to continue

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