Form

As explained in Django in Action

A Django form object is an instance representing form fields, submitted values, and validation errors, and can render its HTML.

A Django Form is a Python object that describes inputs, accepts submitted values, validates them, records errors, and can render the matching HTML. It reduces repetitive form code without taking over the view: the view still decides what happens after valid data arrives. section 7.1 section 7.6

Define a form by subclassing forms.Form and declaring fields. Each field has a widget that renders an HTML control: CharField normally becomes a text input, while an overridden Textarea widget produces a textarea. Widget attributes can set details such as rows, columns, or CSS classes. section 7.1 section 7.6

A comment form

A CommentForm can declare name as a CharField and comment as a CharField using Textarea. Rendering form.as_p produces labels and controls wrapped in paragraphs, including required attributes. This is quick and useful until a design needs markup beyond what automatic rendering supplies. section 7.1 section 7.1.3

A typical view handles both stages of the request. On GET, create an empty form and render it. On POST, construct the form with request.POST and call is_valid(). Invalid input leaves errors on the form and redisplays the page; valid input is available through cleaned_data, after which the view performs its work and redirects. section 7.1.1 section 7.6

Keep these form-handling details straight:

• Use request.method to distinguish displaying the form from processing a submission; the usual single-view pattern posts back to the same URL. section 7.1.1
• Call is_valid() before using cleaned_data. Its result reflects the declared fields and their configuration. section 7.1.1
• Put {% csrf_token %} inside a POST form to add protection against cross-site request forgery. section 7.1.1 section 7.6
• For custom layouts, render individual fields and use their value, help text, and errors; preserve Django's expected name and id conventions in handwritten controls. section 7.1.3

Figure 7.2 Logic flow for a view that handles form submission

The request-flow diagram shows the core loop: GET displays an empty form, POST validates submitted data, invalid data returns with errors, and valid data redirects. section 7.1.1

Automatic rendering is a convenience, not a cage. CSS classes can be added through widget attributes, but frameworks such as Bootstrap may require wrapper markup that a Form cannot generate. In that case, retain the Form for values, help text, and errors while writing the HTML yourself. section 7.1.3

How Django in Action covers it

How deep it goes

Works through field and widget definitions, GET/POST control flow, validation, cleaned data, errors, and custom rendering.

Examples

Demonstrates a CommentForm, a comment view that sends email and redirects, and a manually marked-up Bootstrap first-name field.

What it assumes

Introduces forms through familiar login fields while explaining HTTP GET and POST as the request methods behind display and submission.

What you can do after

Apply it via Django Form to render inputs, validate POST data, display errors, and redirect after successful processing.

How it connects

Connects Form to HTTP GET and POST, widgets, templates, CSRF protection, validation, cleaned_data, and Bootstrap.

liveBookmanning.com

Read Django in Action on liveBook Get the book at manning.com

Related concepts

• ModelFormincludes · A ModelForm is a Django form class generated from a model that maps form fields to model fields and can create or update model instances.
• web formuses · A web form is a browser interface that groups controls for collecting structured user input and submitting it to an application or server.
• form fieldhas part · A form field is a user-interface control or component that represents data to be entered or selected in a form, often with associated rendering or validation behavior.
• dependencyimplemented by · A software dependency is a component, resource, or prerequisite on which another software component or operation relies to function or proceed.
• HTMLproduces · HTML (HyperText Markup Language) is the standard markup language for structuring content and elements in web documents.

This explainer was generated by Manning's knowledge graph from the text of Django in Action. The section links point to the parts of the book it draws on.