Working with forms¶

About this document

This document provides an introduction to Django’s form handling features. For a more detailed look at the forms API, see The Forms API. For documentation of the available field types, see Form fields.

django.forms is Django’s form-handling library.

While it is possible to process form submissions just using Django’s HttpRequest class, using the form library takes care of a number of common form-related tasks. Using it, you can:

Display an HTML form with automatically generated form widgets.
Check submitted data against a set of validation rules.
Redisplay a form in the case of validation errors.
Convert submitted form data to the relevant Python data types.

Overview¶

The library deals with these concepts:

Widget: A class that corresponds to an HTML form widget, e.g. <input type="text"> or <textarea>. This handles rendering of the widget as HTML.
Field: A class that is responsible for doing validation, e.g. an EmailField that makes sure its data is a valid e-mail address.
Form: A collection of fields that knows how to validate itself and display itself as HTML.
Form Media: The CSS and JavaScript resources that are required to render a form.

The library is decoupled from the other Django components, such as the database layer, views and templates. It relies only on Django settings, a couple of django.utils helper functions and Django’s internationalization hooks (but you’re not required to be using internationalization features to use this library).

Form objects¶

A Form object encapsulates a sequence of form fields and a collection of validation rules that must be fulfilled in order for the form to be accepted. Form classes are created as subclasses of django.forms.Form and make use of a declarative style that you’ll be familiar with if you’ve used Django’s database models.

For example, consider a form used to implement “contact me” functionality on a personal Web site:

from django import forms

class ContactForm(forms.Form):
    subject = forms.CharField(max_length=100)
    message = forms.CharField()
    sender = forms.EmailField()
    cc_myself = forms.BooleanField(required=False)

A form is composed of Field objects. In this case, our form has four fields: subject, message, sender and cc_myself. CharField, EmailField and BooleanField are just three of the available field types; a full list can be found in Form fields.

If your form is going to be used to directly add or edit a Django model, you can use a ModelForm to avoid duplicating your model description.

Using a form in a view¶

The standard pattern for processing a form in a view looks like this:

def contact(request):
    if request.method == 'POST': # If the form has been submitted...
        form = ContactForm(request.POST) # A form bound to the POST data
        if form.is_valid(): # All validation rules pass
            # Process the data in form.cleaned_data
            # ...
            return HttpResponseRedirect('/thanks/') # Redirect after POST
    else:
        form = ContactForm() # An unbound form

    return render_to_response('contact.html', {
        'form': form,
    })

There are three code paths here:

If the form has not been submitted, an unbound instance of ContactForm is created and passed to the template.
If the form has been submitted, a bound instance of the form is created using request.POST. If the submitted data is valid, it is processed and the user is re-directed to a "thanks" page.
If the form has been submitted but is invalid, the bound form instance is passed on to the template.

Changed in Django 1.0: The cleaned_data attribute was called clean_data in earlier releases.

The distinction between bound and unbound forms is important. An unbound form does not have any data associated with it; when rendered to the user, it will be empty or will contain default values. A bound form does have submitted data, and hence can be used to tell if that data is valid. If an invalid bound form is rendered it can include inline error messages telling the user where they went wrong.

See Bound and unbound forms for further information on the differences between bound and unbound forms.

Handling file uploads with a form¶

To see how to handle file uploads with your form see Binding uploaded files to a form for more information.

Processing the data from a form¶

Once is_valid() returns True, you can process the form submission safe in the knowledge that it conforms to the validation rules defined by your form. While you could access request.POST directly at this point, it is better to access form.cleaned_data. This data has not only been validated but will also be converted in to the relevant Python types for you. In the above example, cc_myself will be a boolean value. Likewise, fields such as IntegerField and FloatField convert values to a Python int and float respectively.

Extending the above example, here's how the form data could be processed:

if form.is_valid():
    subject = form.cleaned_data['subject']
    message = form.cleaned_data['message']
    sender = form.cleaned_data['sender']
    cc_myself = form.cleaned_data['cc_myself']

    recipients = ['info@example.com']
    if cc_myself:
        recipients.append(sender)

    from django.core.mail import send_mail
    send_mail(subject, message, sender, recipients)
    return HttpResponseRedirect('/thanks/') # Redirect after POST

For more on sending e-mail from Django, see Sending e-mail.

Displaying a form using a template¶

Forms are designed to work with the Django template language. In the above example, we passed our ContactForm instance to the template using the context variable form. Here's a simple example template:

<form action="/contact/" method="post">
{{ form.as_p }}
<input type="submit" value="Submit" />
</form>

The form only outputs its own fields; it is up to you to provide the surrounding <form> tags and the submit button.

form.as_p will output the form with each form field and accompanying label wrapped in a paragraph. Here's the output for our example template:

<form action="/contact/" method="post">
<p><label for="id_subject">Subject:</label>
    <input id="id_subject" type="text" name="subject" maxlength="100" /></p>
<p><label for="id_message">Message:</label>
    <input type="text" name="message" id="id_message" /></p>
<p><label for="id_sender">Sender:</label>
    <input type="text" name="sender" id="id_sender" /></p>
<p><label for="id_cc_myself">Cc myself:</label>
    <input type="checkbox" name="cc_myself" id="id_cc_myself" /></p>
<input type="submit" value="Submit" />
</form>

Note that each form field has an ID attribute set to id_<field-name>, which is referenced by the accompanying label tag. This is important for ensuring forms are accessible to assistive technology such as screen reader software. You can also customize the way in which labels and ids are generated.

You can also use form.as_table to output table rows (you'll need to provide your own <table> tags) and form.as_ul to output list items.

Customizing the form template¶

If the default generated HTML is not to your taste, you can completely customize the way a form is presented using the Django template language. Extending the above example:

<form action="/contact/" method="post">
    <div class="fieldWrapper">
        {{ form.subject.errors }}
        <label for="id_subject">E-mail subject:</label>
        {{ form.subject }}
    </div>
    <div class="fieldWrapper">
        {{ form.message.errors }}
        <label for="id_message">Your message:</label>
        {{ form.message }}
    </div>
    <div class="fieldWrapper">
        {{ form.sender.errors }}
        <label for="id_sender">Your email address:</label>
        {{ form.sender }}
    </div>
    <div class="fieldWrapper">
        {{ form.cc_myself.errors }}
        <label for="id_cc_myself">CC yourself?</label>
        {{ form.cc_myself }}
    </div>
    <p><input type="submit" value="Send message" /></p>
</form>

Each named form-field can be output to the template using {{ form.name_of_field }}, which will produce the HTML needed to display the form widget. Using {{ form.name_of_field.errors }} displays a list of form errors, rendered as an unordered list. This might look like:

<ul class="errorlist">
    <li>Sender is required.</li>
</ul>

The list has a CSS class of errorlist to allow you to style its appearance. If you wish to further customize the display of errors you can do so by looping over them:

{% if form.subject.errors %}
    <ol>
    {% for error in form.subject.errors %}
        <li><strong>{{ error|escape }}</strong></li>
    {% endfor %}
    </ol>
{% endif %}

Looping over the form's fields¶

If you're using the same HTML for each of your form fields, you can reduce duplicate code by looping through each field in turn using a {% for %} loop:

<form action="/contact/" method="post">
    {% for field in form %}
        <div class="fieldWrapper">
            {{ field.errors }}
            {{ field.label_tag }}: {{ field }}
        </div>
    {% endfor %}
    <p><input type="submit" value="Send message" /></p>
</form>

Within this loop, {{ field }} is an instance of BoundField. BoundField also has the following attributes, which can be useful in your templates:

{{ field.label }}

The label of the field, e.g. E-mail address.

{{ field.label_tag }}

The field's label wrapped in the appropriate HTML <label> tag, e.g. <label for="id_email">E-mail address</label>

{{ field.html_name }}

The name of the field that will be used in the input element's name field. This takes the form prefix into account, if it has been set.

{{ field.help_text }}

Any help text that has been associated with the field.

{{ field.errors }}

Outputs a <ul class="errorlist"> containing any validation errors corresponding to this field. You can customize the presentation of the errors with a {% for error in field.errors %} loop. In this case, each object in the loop is a simple string containing the error message.

field.is_hidden

This attribute is True if the form field is a hidden field and False otherwise. It's not particularly useful as a template variable, but could be useful in conditional tests such as:

{% if field.is_hidden %}
   {# Do something special #}
{% endif %}

Looping over hidden and visible fields¶

If you're manually laying out a form in a template, as opposed to relying on Django's default form layout, you might want to treat <input type="hidden"> fields differently than non-hidden fields. For example, because hidden fields don't display anything, putting error messages "next to" the field could cause confusion for your users -- so errors for those fields should be handled differently.

Django provides two methods on a form that allow you to loop over the hidden and visible fields independently: hidden_fields() and visible_fields(). Here's a modification of an earlier example that uses these two methods:

<form action="/contact/" method="post">
    {% for field in form.visible_fields %}
        <div class="fieldWrapper">

            {# Include the hidden fields in the form #}
            {% if forloop.first %}
                {% for hidden in form.hidden_fields %}
                {{ hidden }}
                {% endfor %}
            {% endif %}

            {{ field.errors }}
            {{ field.label_tag }}: {{ field }}
        </div>
    {% endfor %}
    <p><input type="submit" value="Send message" /></p>
</form>

This example does not handle any errors in the hidden fields. Usually, an error in a hidden field is a sign of form tampering, since normal form interaction won't alter them. However, you could easily insert some error displays for those form errors, as well.

New in Django 1.1: The hidden_fields and visible_fields methods are new in Django 1.1.

Reusable form templates¶

If your site uses the same rendering logic for forms in multiple places, you can reduce duplication by saving the form's loop in a standalone template and using the include tag to reuse it in other templates:

<form action="/contact/" method="post">
    {% include "form_snippet.html" %}
    <p><input type="submit" value="Send message" /></p>
</form>

# In form_snippet.html:

{% for field in form %}
    <div class="fieldWrapper">
        {{ field.errors }}
        {{ field.label_tag }}: {{ field }}
    </div>
{% endfor %}

If the form object passed to a template has a different name within the context, you can alias it using the with tag:

<form action="/comments/add/" method="post">
    {% with comment_form as form %}
        {% include "form_snippet.html" %}
    {% endwith %}
    <p><input type="submit" value="Submit comment" /></p>
</form>

If you find yourself doing this often, you might consider creating a custom inclusion tag.

Further topics¶

This covers the basics, but forms can do a whole lot more:

Django v1.2 documentation

Working with forms¶

Overview¶

Form objects¶

Using a form in a view¶

Handling file uploads with a form¶

Processing the data from a form¶

Displaying a form using a template¶

Customizing the form template¶

Looping over the form's fields¶

Looping over hidden and visible fields¶

Reusable form templates¶

Further topics¶

Table Of Contents

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You are here:

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Last update:

Django v1.2 documentation

Working with forms¶

Overview¶

Form objects¶

Using a form in a view¶

Handling file uploads with a form¶

Processing the data from a form¶

Displaying a form using a template¶

Customizing the form template¶

Looping over the form's fields¶

Looping over hidden and visible fields¶

Reusable form templates¶

Further topics¶

Table Of Contents

Browse

You are here:

This Page

Quick search

Last update: