=============

The Forms API

=============

.. module:: django.forms

.. admonition:: About this document

    This document covers the gritty details of Django's forms API. You should

    read the :doc:`introduction to working with forms </topics/forms/index>`

    first.

.. _ref-forms-api-bound-unbound:

Bound and unbound forms

=======================

A :class:`Form` instance is either **bound** to a set of data, or **unbound**.

* If it's **bound** to a set of data, it's capable of validating that data

  and rendering the form as HTML with the data displayed in the HTML.

* If it's **unbound**, it cannot do validation (because there's no data to

  validate!), but it can still render the blank form as HTML.

.. class:: Form

To create an unbound :class:`Form` instance, instantiate the class::

    >>> f = ContactForm()

To bind data to a form, pass the data as a dictionary as the first parameter to

your :class:`Form` class constructor::

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

In this dictionary, the keys are the field names, which correspond to the

attributes in your :class:`Form` class. The values are the data you're trying to

validate. These will usually be strings, but there's no requirement that they be

strings; the type of data you pass depends on the :class:`Field`, as we'll see

in a moment.

.. attribute:: Form.is_bound

If you need to distinguish between bound and unbound form instances at runtime,

check the value of the form's :attr:`~Form.is_bound` attribute::

    >>> f = ContactForm()

    >>> f.is_bound

    False

    >>> f = ContactForm({'subject': 'hello'})

    >>> f.is_bound

    True

Note that passing an empty dictionary creates a *bound* form with empty data::

    >>> f = ContactForm({})

    >>> f.is_bound

    True

If you have a bound :class:`Form` instance and want to change the data somehow,

or if you want to bind an unbound :class:`Form` instance to some data, create

another :class:`Form` instance. There is no way to change data in a

:class:`Form` instance. Once a :class:`Form` instance has been created, you

should consider its data immutable, whether it has data or not.

Using forms to validate data

============================

.. method:: Form.clean()

Implement a ``clean()`` method on your ``Form`` when you must add custom

validation for fields that are interdependent. See

:ref:`validating-fields-with-clean` for example usage.

.. method:: Form.is_valid()

The primary task of a :class:`Form` object is to validate data. With a bound

:class:`Form` instance, call the :meth:`~Form.is_valid` method to run validation

and return a boolean designating whether the data was valid::

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

    >>> f.is_valid()

    True

Let's try with some invalid data. In this case, ``subject`` is blank (an error,

because all fields are required by default) and ``sender`` is not a valid

email address::

    >>> data = {'subject': '',

    ...         'message': 'Hi there',

    ...         'sender': 'invalid email address',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

    >>> f.is_valid()

    False

.. attribute:: Form.errors

Access the :attr:`~Form.errors` attribute to get a dictionary of error

messages::

    >>> f.errors

    {'sender': ['Enter a valid email address.'], 'subject': ['This field is required.']}

In this dictionary, the keys are the field names, and the values are lists of

strings representing the error messages. The error messages are stored

in lists because a field can have multiple error messages.

You can access :attr:`~Form.errors` without having to call

:meth:`~Form.is_valid` first. The form's data will be validated the first time

either you call :meth:`~Form.is_valid` or access :attr:`~Form.errors`.

The validation routines will only get called once, regardless of how many times

you access :attr:`~Form.errors` or call :meth:`~Form.is_valid`. This means that

if validation has side effects, those side effects will only be triggered once.

.. method:: Form.errors.as_data()

Returns a ``dict`` that maps fields to their original ``ValidationError``

instances.

    >>> f.errors.as_data()

    {'sender': [ValidationError(['Enter a valid email address.'])],

    'subject': [ValidationError(['This field is required.'])]}

Use this method anytime you need to identify an error by its ``code``. This

enables things like rewriting the error's message or writing custom logic in a

view when a given error is present. It can also be used to serialize the errors

in a custom format (e.g. XML); for instance, :meth:`~Form.errors.as_json()`

relies on ``as_data()``.

The need for the ``as_data()`` method is due to backwards compatibility.

Previously ``ValidationError`` instances were lost as soon as their

**rendered** error messages were added to the ``Form.errors`` dictionary.

Ideally ``Form.errors`` would have stored ``ValidationError`` instances

and methods with an ``as_`` prefix could render them, but it had to be done

the other way around in order not to break code that expects rendered error

messages in ``Form.errors``.

.. method:: Form.errors.as_json(escape_html=False)

Returns the errors serialized as JSON.

    >>> f.errors.as_json()

    {"sender": [{"message": "Enter a valid email address.", "code": "invalid"}],

    "subject": [{"message": "This field is required.", "code": "required"}]}

By default, ``as_json()`` does not escape its output. If you are using it for

something like AJAX requests to a form view where the client interprets the

response and inserts errors into the page, you'll want to be sure to escape the

results on the client-side to avoid the possibility of a cross-site scripting

attack. You can do this in JavaScript with ``element.textContent = errorText``

or with jQuery's ``$(el).text(errorText)`` (rather than its ``.html()``

function).

If for some reason you don't want to use client-side escaping, you can also

set ``escape_html=True`` and error messages will be escaped so you can use them

directly in HTML.

.. method:: Form.errors.get_json_data(escape_html=False)

Returns the errors as a dictionary suitable for serializing to JSON.

:meth:`Form.errors.as_json()` returns serialized JSON, while this returns the

error data before it's serialized.

The ``escape_html`` parameter behaves as described in

:meth:`Form.errors.as_json()`.

.. method:: Form.add_error(field, error)

This method allows adding errors to specific fields from within the

``Form.clean()`` method, or from outside the form altogether; for instance

from a view.

The ``field`` argument is the name of the field to which the errors

should be added. If its value is ``None`` the error will be treated as

a non-field error as returned by :meth:`Form.non_field_errors()

<django.forms.Form.non_field_errors>`.

The ``error`` argument can be a string, or preferably an instance of

``ValidationError``. See :ref:`raising-validation-error` for best practices

when defining form errors.

Note that ``Form.add_error()`` automatically removes the relevant field from

``cleaned_data``.

.. method:: Form.has_error(field, code=None)

This method returns a boolean designating whether a field has an error with

a specific error ``code``. If ``code`` is ``None``, it will return ``True``

if the field contains any errors at all.

To check for non-field errors use

:data:`~django.core.exceptions.NON_FIELD_ERRORS` as the ``field`` parameter.

.. method:: Form.non_field_errors()

This method returns the list of errors from :attr:`Form.errors

<django.forms.Form.errors>`  that aren't associated with a particular field.

This includes ``ValidationError``\s that are raised in :meth:`Form.clean()

<django.forms.Form.clean>` and errors added using :meth:`Form.add_error(None,

"...") <django.forms.Form.add_error>`.

Behavior of unbound forms

-------------------------

It's meaningless to validate a form with no data, but, for the record, here's

what happens with unbound forms::

    >>> f = ContactForm()

    >>> f.is_valid()

    False

    >>> f.errors

    {}

.. _ref-forms-initial-form-values:

Initial form values

===================

.. attribute:: Form.initial

Use :attr:`~Form.initial` to declare the initial value of form fields at

runtime. For example, you might want to fill in a ``username`` field with the

username of the current session.

To accomplish this, use the :attr:`~Form.initial` argument to a :class:`Form`.

This argument, if given, should be a dictionary mapping field names to initial

values. Only include the fields for which you're specifying an initial value;

it's not necessary to include every field in your form. For example::

    >>> f = ContactForm(initial={'subject': 'Hi there!'})

These values are only displayed for unbound forms, and they're not used as

fallback values if a particular value isn't provided.

If a :class:`~django.forms.Field` defines :attr:`~Field.initial` *and* you

include :attr:`~Form.initial` when instantiating the ``Form``, then the latter

``initial`` will have precedence. In this example, ``initial`` is provided both

at the field level and at the form instance level, and the latter gets

precedence::

    >>> from django import forms

    >>> class CommentForm(forms.Form):

    ...     name = forms.CharField(initial='class')

    ...     url = forms.URLField()

    ...     comment = forms.CharField()

    >>> f = CommentForm(initial={'name': 'instance'}, auto_id=False)

    >>> print(f)

    <tr><th>Name:</th><td><input type="text" name="name" value="instance" required></td></tr>

    <tr><th>Url:</th><td><input type="url" name="url" required></td></tr>

    <tr><th>Comment:</th><td><input type="text" name="comment" required></td></tr>

.. method:: Form.get_initial_for_field(field, field_name)

Returns the initial data for a form field. It retrieves the data from

:attr:`Form.initial` if present, otherwise trying :attr:`Field.initial`.

Callable values are evaluated.

It is recommended to use :attr:`BoundField.initial` over

:meth:`~Form.get_initial_for_field()` because ``BoundField.initial`` has a

simpler interface. Also, unlike :meth:`~Form.get_initial_for_field()`,

:attr:`BoundField.initial` caches its values. This is useful especially when

dealing with callables whose return values can change (e.g. ``datetime.now`` or

``uuid.uuid4``)::

    >>> import uuid

    >>> class UUIDCommentForm(CommentForm):

    ...     identifier = forms.UUIDField(initial=uuid.uuid4)

    >>> f = UUIDCommentForm()

    >>> f.get_initial_for_field(f.fields['identifier'], 'identifier')

    UUID('972ca9e4-7bfe-4f5b-af7d-07b3aa306334')

    >>> f.get_initial_for_field(f.fields['identifier'], 'identifier')

    UUID('1b411fab-844e-4dec-bd4f-e9b0495f04d0')

    >>> # Using BoundField.initial, for comparison

    >>> f['identifier'].initial

    UUID('28a09c59-5f00-4ed9-9179-a3b074fa9c30')

    >>> f['identifier'].initial

    UUID('28a09c59-5f00-4ed9-9179-a3b074fa9c30')

Checking which form data has changed

====================================

.. method:: Form.has_changed()

Use the ``has_changed()`` method on your ``Form`` when you need to check if the

form data has been changed from the initial data.

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> f = ContactForm(data, initial=data)

    >>> f.has_changed()

    False

When the form is submitted, we reconstruct it and provide the original data

so that the comparison can be done:

    >>> f = ContactForm(request.POST, initial=data)

    >>> f.has_changed()

``has_changed()`` will be ``True`` if the data from ``request.POST`` differs

from what was provided in :attr:`~Form.initial` or ``False`` otherwise. The

result is computed by calling :meth:`Field.has_changed` for each field in the

form.

.. attribute:: Form.changed_data

The ``changed_data`` attribute returns a list of the names of the fields whose

values in the form's bound data (usually ``request.POST``) differ from what was

provided in :attr:`~Form.initial`. It returns an empty list if no data differs.

    >>> f = ContactForm(request.POST, initial=data)

    >>> if f.has_changed():

    ...     print("The following fields changed: %s" % ", ".join(f.changed_data))

    >>> f.changed_data

    ['subject', 'message']

Accessing the fields from the form

==================================

.. attribute:: Form.fields

You can access the fields of :class:`Form` instance from its ``fields``

attribute::

    >>> for row in f.fields.values(): print(row)

    ...

    <django.forms.fields.CharField object at 0x7ffaac632510>

    <django.forms.fields.URLField object at 0x7ffaac632f90>

    <django.forms.fields.CharField object at 0x7ffaac3aa050>

    >>> f.fields['name']

    <django.forms.fields.CharField object at 0x7ffaac6324d0>

You can alter the field and :class:`.BoundField` of :class:`Form` instance to

change the way it is presented in the form::

    >>> f.as_div().split("</div>")[0]

    '<div><label for="id_subject">Subject:</label><input type="text" name="subject" maxlength="100" required id="id_subject">'

    >>> f["subject"].label = "Topic"

    >>> f.as_div().split("</div>")[0]

    '<div><label for="id_subject">Topic:</label><input type="text" name="subject" maxlength="100" required id="id_subject">'

Beware not to alter the ``base_fields`` attribute because this modification

will influence all subsequent ``ContactForm`` instances within the same Python

process::

    >>> f.base_fields["subject"].label_suffix = "?"

    >>> another_f = CommentForm(auto_id=False)

    >>> f.as_div().split("</div>")[0]

    '<div><label for="id_subject">Subject?</label><input type="text" name="subject" maxlength="100" required id="id_subject">'

Accessing "clean" data

======================

.. attribute:: Form.cleaned_data

Each field in a :class:`Form` class is responsible not only for validating

data, but also for "cleaning" it -- normalizing it to a consistent format. This

is a nice feature, because it allows data for a particular field to be input in

a variety of ways, always resulting in consistent output.

For example, :class:`~django.forms.DateField` normalizes input into a

Python ``datetime.date`` object. Regardless of whether you pass it a string in

the format ``'1994-07-15'``, a ``datetime.date`` object, or a number of other

formats, ``DateField`` will always normalize it to a ``datetime.date`` object

as long as it's valid.

Once you've created a :class:`~Form` instance with a set of data and validated

it, you can access the clean data via its ``cleaned_data`` attribute::

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

    >>> f.is_valid()

    True

    >>> f.cleaned_data

    {'cc_myself': True, 'message': 'Hi there', 'sender': '[email protected]', 'subject': 'hello'}

Note that any text-based field -- such as ``CharField`` or ``EmailField`` --

always cleans the input into a string. We'll cover the encoding implications

later in this document.

If your data does *not* validate, the ``cleaned_data`` dictionary contains

only the valid fields::

    >>> data = {'subject': '',

    ...         'message': 'Hi there',

    ...         'sender': 'invalid email address',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

    >>> f.is_valid()

    False

    >>> f.cleaned_data

    {'cc_myself': True, 'message': 'Hi there'}

``cleaned_data`` will always *only* contain a key for fields defined in the

``Form``, even if you pass extra data when you define the ``Form``. In this

example, we pass a bunch of extra fields to the ``ContactForm`` constructor,

but ``cleaned_data`` contains only the form's fields::

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True,

    ...         'extra_field_1': 'foo',

    ...         'extra_field_2': 'bar',

    ...         'extra_field_3': 'baz'}

    >>> f = ContactForm(data)

    >>> f.is_valid()

    True

    >>> f.cleaned_data # Doesn't contain extra_field_1, etc.

    {'cc_myself': True, 'message': 'Hi there', 'sender': '[email protected]', 'subject': 'hello'}

When the ``Form`` is valid, ``cleaned_data`` will include a key and value for

*all* its fields, even if the data didn't include a value for some optional

fields. In this example, the data dictionary doesn't include a value for the

``nick_name`` field, but ``cleaned_data`` includes it, with an empty value::

    >>> from django import forms

    >>> class OptionalPersonForm(forms.Form):

    ...     first_name = forms.CharField()

    ...     last_name = forms.CharField()

    ...     nick_name = forms.CharField(required=False)

    >>> data = {'first_name': 'John', 'last_name': 'Lennon'}

    >>> f = OptionalPersonForm(data)

    >>> f.is_valid()

    True

    >>> f.cleaned_data

    {'nick_name': '', 'first_name': 'John', 'last_name': 'Lennon'}

In this above example, the ``cleaned_data`` value for ``nick_name`` is set to an

empty string, because ``nick_name`` is ``CharField``, and ``CharField``\s treat

empty values as an empty string. Each field type knows what its "blank" value

is -- e.g., for ``DateField``, it's ``None`` instead of the empty string. For

full details on each field's behavior in this case, see the "Empty value" note

for each field in the "Built-in ``Field`` classes" section below.

You can write code to perform validation for particular form fields (based on

their name) or for the form as a whole (considering combinations of various

fields). More information about this is in :doc:`/ref/forms/validation`.

.. _ref-forms-api-outputting-html:

Outputting forms as HTML

========================

The second task of a ``Form`` object is to render itself as HTML. To do so,

``print`` it::

    >>> f = ContactForm()

    >>> print(f)

    <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" required></td></tr>

    <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" required></td></tr>

    <tr><th><label for="id_sender">Sender:</label></th><td><input type="email" name="sender" id="id_sender" required></td></tr>

    <tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself"></td></tr>

If the form is bound to data, the HTML output will include that data

appropriately. For example, if a field is represented by an

``<input type="text">``, the data will be in the ``value`` attribute. If a

field is represented by an ``<input type="checkbox">``, then that HTML will

include ``checked`` if appropriate::

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> f = ContactForm(data)

    >>> print(f)

    <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" value="hello" required></td></tr>

    <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" value="Hi there" required></td></tr>

    <tr><th><label for="id_sender">Sender:</label></th><td><input type="email" name="sender" id="id_sender" value="[email protected]" required></td></tr>

    <tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" checked></td></tr>

This default output is a two-column HTML table, with a ``<tr>`` for each field.

Notice the following:

* For flexibility, the output does *not* include the ``<table>`` and

  ``</table>`` tags, nor does it include the ``<form>`` and ``</form>``

  tags or an ``<input type="submit">`` tag. It's your job to do that.

* Each field type has a default HTML representation. ``CharField`` is

  represented by an ``<input type="text">`` and ``EmailField`` by an

  ``<input type="email">``. ``BooleanField(null=False)`` is represented by an

  ``<input type="checkbox">``. Note these are merely sensible defaults; you can

  specify which HTML to use for a given field by using widgets, which we'll

  explain shortly.

* The HTML ``name`` for each tag is taken directly from its attribute name

  in the ``ContactForm`` class.

* The text label for each field -- e.g. ``'Subject:'``, ``'Message:'`` and

  ``'Cc myself:'`` is generated from the field name by converting all

  underscores to spaces and upper-casing the first letter. Again, note

  these are merely sensible defaults; you can also specify labels manually.

* Each text label is surrounded in an HTML ``<label>`` tag, which points

  to the appropriate form field via its ``id``. Its ``id``, in turn, is

  generated by prepending ``'id_'`` to the field name. The ``id``

  attributes and ``<label>`` tags are included in the output by default, to

  follow best practices, but you can change that behavior.

* The output uses HTML5 syntax, targeting ``<!DOCTYPE html>``. For example,

  it uses boolean attributes such as ``checked`` rather than the XHTML style

  of ``checked='checked'``.

Although ``<table>`` output is the default output style when you ``print`` a

form, other output styles are available. Each style is available as a method on

a form object, and each rendering method returns a string.

Default rendering

-----------------

The default rendering when you ``print`` a form uses the following methods and

attributes.

``template_name``

~~~~~~~~~~~~~~~~~

.. versionadded:: 4.0

.. attribute:: Form.template_name

The name of the template rendered if the form is cast into a string, e.g. via

``print(form)`` or in a template via ``{{ form }}``.

By default, a property returning the value of the renderer's

:attr:`~django.forms.renderers.BaseRenderer.form_template_name`. You may set it

as a string template name in order to override that for a particular form

class.

.. versionchanged:: 4.1

    In older versions ``template_name`` defaulted to the string value

    ``'django/forms/default.html'``.

``render()``

~~~~~~~~~~~~

.. versionadded:: 4.0

.. method:: Form.render(template_name=None, context=None, renderer=None)

The render method is called by ``__str__`` as well as the

:meth:`.Form.as_table`, :meth:`.Form.as_p`, and :meth:`.Form.as_ul` methods.

All arguments are optional and default to:

* ``template_name``: :attr:`.Form.template_name`

* ``context``: Value returned by :meth:`.Form.get_context`

* ``renderer``: Value returned by :attr:`.Form.default_renderer`

By passing ``template_name`` you can customize the template used for just a

single call.

``get_context()``

~~~~~~~~~~~~~~~~~

.. versionadded:: 4.0

.. method:: Form.get_context()

Return the template context for rendering the form.

The available context is:

* ``form``: The bound form.

* ``fields``: All bound fields, except the hidden fields.

* ``hidden_fields``: All hidden bound fields.

* ``errors``: All non field related or hidden field related form errors.

``template_name_label``

~~~~~~~~~~~~~~~~~~~~~~~

.. versionadded:: 4.0

.. attribute:: Form.template_name_label

The template used to render a field's ``<label>``, used when calling

:meth:`BoundField.label_tag`/:meth:`~BoundField.legend_tag`. Can be changed per

form by overriding this attribute or more generally by overriding the default

template, see also :ref:`overriding-built-in-form-templates`.

Output styles

-------------

As well as rendering the form directly, such as in a template with

``{{ form }}``, the following helper functions serve as a proxy to

:meth:`Form.render` passing a particular ``template_name`` value.

These helpers are most useful in a template, where you need to override the

form renderer or form provided value but cannot pass the additional parameter

to :meth:`~Form.render`. For example, you can render a form as an unordered

list using ``{{ form.as_ul }}``.

Each helper pairs a form method with an attribute giving the appropriate

template name.

``as_div()``

~~~~~~~~~~~~

.. attribute:: Form.template_name_div

.. versionadded:: 4.1

The template used by ``as_div()``. Default: ``'django/forms/div.html'``.

.. method:: Form.as_div()

.. versionadded:: 4.1

``as_div()`` renders the form as a series of ``<div>`` elements, with each

``<div>`` containing one field, such as:

.. code-block:: pycon

    >>> f = ContactForm()

    >>> f.as_div()

… gives HTML like:

.. code-block:: html

    <div>

    <label for="id_subject">Subject:</label>

    <input type="text" name="subject" maxlength="100" required id="id_subject">

    </div>

    <div>

    <label for="id_message">Message:</label>

    <input type="text" name="message" required id="id_message">

    </div>

    <div>

    <label for="id_sender">Sender:</label>

    <input type="email" name="sender" required id="id_sender">

    </div>

    <div>

    <label for="id_cc_myself">Cc myself:</label>

    <input type="checkbox" name="cc_myself" id="id_cc_myself">

    </div>

.. note::

    Of the framework provided templates and output styles, ``as_div()`` is

    recommended over the ``as_p()``, ``as_table()``, and ``as_ul()`` versions

    as the template implements ``<fieldset>`` and ``<legend>`` to group related

    inputs and is easier for screen reader users to navigate.

``as_p()``

~~~~~~~~~~

.. attribute:: Form.template_name_p

The template used by ``as_p()``. Default: ``'django/forms/p.html'``.

.. method:: Form.as_p()

``as_p()`` renders the form as a series of ``<p>`` tags, with each ``<p>``

containing one field::

    >>> f = ContactForm()

    >>> f.as_p()

    '<p><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" required></p>\n<p><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" required></p>\n<p><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" required></p>\n<p><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself"></p>'

    >>> print(f.as_p())

    <p><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" required></p>

    <p><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" required></p>

    <p><label for="id_sender">Sender:</label> <input type="email" name="sender" id="id_sender" required></p>

    <p><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself"></p>

``as_ul()``

~~~~~~~~~~~

.. attribute:: Form.template_name_ul

The template used by ``as_ul()``. Default: ``'django/forms/ul.html'``.

.. method:: Form.as_ul()

``as_ul()`` renders the form as a series of ``<li>`` tags, with each ``<li>``

containing one field. It does *not* include the ``<ul>`` or ``</ul>``, so that

you can specify any HTML attributes on the ``<ul>`` for flexibility::

    >>> f = ContactForm()

    >>> f.as_ul()

    '<li><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" required></li>\n<li><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" required></li>\n<li><label for="id_sender">Sender:</label> <input type="email" name="sender" id="id_sender" required></li>\n<li><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself"></li>'

    >>> print(f.as_ul())

    <li><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" required></li>

    <li><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" required></li>

    <li><label for="id_sender">Sender:</label> <input type="email" name="sender" id="id_sender" required></li>

    <li><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself"></li>

``as_table()``

~~~~~~~~~~~~~~

.. attribute:: Form.template_name_table

The template used by ``as_table()``. Default: ``'django/forms/table.html'``.

.. method:: Form.as_table()

``as_table()`` renders the form as an HTML ``<table>``::

    >>> f = ContactForm()

    >>> f.as_table()

    '<tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" required></td></tr>\n<tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" required></td></tr>\n<tr><th><label for="id_sender">Sender:</label></th><td><input type="email" name="sender" id="id_sender" required></td></tr>\n<tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself"></td></tr>'

    >>> print(f)

    <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" required></td></tr>

    <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" required></td></tr>

    <tr><th><label for="id_sender">Sender:</label></th><td><input type="email" name="sender" id="id_sender" required></td></tr>

    <tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself"></td></tr>

.. _ref-forms-api-styling-form-rows:

Styling required or erroneous form rows

---------------------------------------

.. attribute:: Form.error_css_class

.. attribute:: Form.required_css_class

It's pretty common to style form rows and fields that are required or have

errors. For example, you might want to present required form rows in bold and

highlight errors in red.

The :class:`Form` class has a couple of hooks you can use to add ``class``

attributes to required rows or to rows with errors: set the

:attr:`Form.error_css_class` and/or :attr:`Form.required_css_class`

attributes::

    from django import forms

    class ContactForm(forms.Form):

        error_css_class = 'error'

        required_css_class = 'required'

        # ... and the rest of your fields here

Once you've done that, rows will be given ``"error"`` and/or ``"required"``

classes, as needed. The HTML will look something like::

    >>> f = ContactForm(data)

    >>> print(f.as_table())

    <tr class="required"><th><label class="required" for="id_subject">Subject:</label>    ...

    <tr class="required"><th><label class="required" for="id_message">Message:</label>    ...

    <tr class="required error"><th><label class="required" for="id_sender">Sender:</label>      ...

    <tr><th><label for="id_cc_myself">Cc myself:<label> ...

    >>> f['subject'].label_tag()

    <label class="required" for="id_subject">Subject:</label>

    >>> f['subject'].legend_tag()

    <legend class="required" for="id_subject">Subject:</legend>

    >>> f['subject'].label_tag(attrs={'class': 'foo'})

    <label for="id_subject" class="foo required">Subject:</label>

    >>> f['subject'].legend_tag(attrs={'class': 'foo'})

    <legend for="id_subject" class="foo required">Subject:</legend>

.. _ref-forms-api-configuring-label:

Configuring form elements' HTML ``id`` attributes and ``<label>`` tags

----------------------------------------------------------------------

.. attribute:: Form.auto_id

By default, the form rendering methods include:

* HTML ``id`` attributes on the form elements.

* The corresponding ``<label>`` tags around the labels. An HTML ``<label>`` tag

  designates which label text is associated with which form element. This small

  enhancement makes forms more usable and more accessible to assistive devices.

  It's always a good idea to use ``<label>`` tags.

The ``id`` attribute values are generated by prepending ``id_`` to the form

field names.  This behavior is configurable, though, if you want to change the

``id`` convention or remove HTML ``id`` attributes and ``<label>`` tags

entirely.

Use the ``auto_id`` argument to the ``Form`` constructor to control the ``id``

and label behavior. This argument must be ``True``, ``False`` or a string.

If ``auto_id`` is ``False``, then the form output will not include ``<label>``

tags nor ``id`` attributes::

    >>> f = ContactForm(auto_id=False)

    >>> print(f.as_div())

    <div>Subject:<input type="text" name="subject" maxlength="100" required></div>

    <div>Message:<textarea name="message" cols="40" rows="10" required></textarea></div>

    <div>Sender:<input type="email" name="sender" required></div>

    <div>Cc myself:<input type="checkbox" name="cc_myself"></div>

If ``auto_id`` is set to ``True``, then the form output *will* include

``<label>`` tags and will use the field name as its ``id`` for each form

field::

    >>> f = ContactForm(auto_id=True)

    >>> print(f.as_div())

    <div><label for="subject">Subject:</label><input type="text" name="subject" maxlength="100" required id="subject"></div>

    <div><label for="message">Message:</label><textarea name="message" cols="40" rows="10" required id="message"></textarea></div>

    <div><label for="sender">Sender:</label><input type="email" name="sender" required id="sender"></div>

    <div><label for="cc_myself">Cc myself:</label><input type="checkbox" name="cc_myself" id="cc_myself"></div>

If ``auto_id`` is set to a string containing the format character ``'%s'``,

then the form output will include ``<label>`` tags, and will generate ``id``

attributes based on the format string. For example, for a format string

``'field_%s'``, a field named ``subject`` will get the ``id`` value

``'field_subject'``. Continuing our example::

    >>> f = ContactForm(auto_id='id_for_%s')

    >>> print(f.as_div())

    <div><label for="id_for_subject">Subject:</label><input type="text" name="subject" maxlength="100" required id="id_for_subject"></div>

    <div><label for="id_for_message">Message:</label><textarea name="message" cols="40" rows="10" required id="id_for_message"></textarea></div>

    <div><label for="id_for_sender">Sender:</label><input type="email" name="sender" required id="id_for_sender"></div>

    <div><label for="id_for_cc_myself">Cc myself:</label><input type="checkbox" name="cc_myself" id="id_for_cc_myself"></div>

If ``auto_id`` is set to any other true value -- such as a string that doesn't

include ``%s`` -- then the library will act as if ``auto_id`` is ``True``.

By default, ``auto_id`` is set to the string ``'id_%s'``.

.. attribute:: Form.label_suffix

A translatable string (defaults to a colon (``:``) in English) that will be

appended after any label name when a form is rendered.

It's possible to customize that character, or omit it entirely, using the

``label_suffix`` parameter::

    >>> f = ContactForm(auto_id='id_for_%s', label_suffix='')

    >>> print(f.as_div())

    <div><label for="id_for_subject">Subject</label><input type="text" name="subject" maxlength="100" required id="id_for_subject"></div>

    <div><label for="id_for_message">Message</label><textarea name="message" cols="40" rows="10" required id="id_for_message"></textarea></div>

    <div><label for="id_for_sender">Sender</label><input type="email" name="sender" required id="id_for_sender"></div>

    <div><label for="id_for_cc_myself">Cc myself</label><input type="checkbox" name="cc_myself" id="id_for_cc_myself"></div>

    >>> f = ContactForm(auto_id='id_for_%s', label_suffix=' ->')

    >>> print(f.as_div())

    <div><label for="id_for_subject">Subject:</label><input type="text" name="subject" maxlength="100" required id="id_for_subject"></div>

    <div><label for="id_for_message">Message -&gt;</label><textarea name="message" cols="40" rows="10" required id="id_for_message"></textarea></div>

    <div><label for="id_for_sender">Sender -&gt;</label><input type="email" name="sender" required id="id_for_sender"></div>

    <div><label for="id_for_cc_myself">Cc myself -&gt;</label><input type="checkbox" name="cc_myself" id="id_for_cc_myself"></div>

Note that the label suffix is added only if the last character of the

label isn't a punctuation character (in English, those are ``.``, ``!``, ``?``

or ``:``).

Fields can also define their own :attr:`~django.forms.Field.label_suffix`.

This will take precedence over :attr:`Form.label_suffix

<django.forms.Form.label_suffix>`. The suffix can also be overridden at runtime

using the ``label_suffix`` parameter to

:meth:`~django.forms.BoundField.label_tag`/

:meth:`~django.forms.BoundField.legend_tag`.

.. attribute:: Form.use_required_attribute

When set to ``True`` (the default), required form fields will have the

``required`` HTML attribute.

:doc:`Formsets </topics/forms/formsets>` instantiate forms with

``use_required_attribute=False`` to avoid incorrect browser validation when

adding and deleting forms from a formset.

Configuring the rendering of a form's widgets

---------------------------------------------

.. attribute:: Form.default_renderer

Specifies the :doc:`renderer <renderers>` to use for the form. Defaults to

``None`` which means to use the default renderer specified by the

:setting:`FORM_RENDERER` setting.

You can set this as a class attribute when declaring your form or use the

``renderer`` argument to ``Form.__init__()``. For example::

    from django import forms

    class MyForm(forms.Form):

        default_renderer = MyRenderer()

or::

    form = MyForm(renderer=MyRenderer())

Notes on field ordering

-----------------------

In the ``as_p()``, ``as_ul()`` and ``as_table()`` shortcuts, the fields are

displayed in the order in which you define them in your form class. For

example, in the ``ContactForm`` example, the fields are defined in the order

``subject``, ``message``, ``sender``, ``cc_myself``. To reorder the HTML

output, change the order in which those fields are listed in the class.

There are several other ways to customize the order:

.. attribute:: Form.field_order

By default ``Form.field_order=None``, which retains the order in which you

define the fields in your form class. If ``field_order`` is a list of field

names, the fields are ordered as specified by the list and remaining fields are

appended according to the default order. Unknown field names in the list are

ignored. This makes it possible to disable a field in a subclass by setting it

to ``None`` without having to redefine ordering.

You can also use the ``Form.field_order`` argument to a :class:`Form` to

override the field order. If a :class:`~django.forms.Form` defines

:attr:`~Form.field_order` *and* you include ``field_order`` when instantiating

the ``Form``, then the latter ``field_order`` will have precedence.

.. method:: Form.order_fields(field_order)

You may rearrange the fields any time using ``order_fields()`` with a list of

field names as in :attr:`~django.forms.Form.field_order`.

How errors are displayed

------------------------

If you render a bound ``Form`` object, the act of rendering will automatically

run the form's validation if it hasn't already happened, and the HTML output

will include the validation errors as a ``<ul class="errorlist">`` near the

field. The particular positioning of the error messages depends on the output

method you're using::

    >>> data = {'subject': '',

    ...         'message': 'Hi there',

    ...         'sender': 'invalid email address',

    ...         'cc_myself': True}

    >>> f = ContactForm(data, auto_id=False)

    >>> print(f.as_div())

    <div>Subject:<ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="subject" maxlength="100" required></div>

    <div>Message:<textarea name="message" cols="40" rows="10" required>Hi there</textarea></div>

    <div>Sender:<ul class="errorlist"><li>Enter a valid email address.</li></ul><input type="email" name="sender" value="invalid email address" required></div>

    <div>Cc myself:<input type="checkbox" name="cc_myself" checked></div>

    >>> print(f.as_table())

    <tr><th>Subject:</th><td><ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="subject" maxlength="100" required></td></tr>

    <tr><th>Message:</th><td><textarea name="message" cols="40" rows="10" required></textarea></td></tr>

    <tr><th>Sender:</th><td><ul class="errorlist"><li>Enter a valid email address.</li></ul><input type="email" name="sender" value="invalid email address" required></td></tr>

    <tr><th>Cc myself:</th><td><input checked type="checkbox" name="cc_myself"></td></tr>

    >>> print(f.as_ul())

    <li><ul class="errorlist"><li>This field is required.</li></ul>Subject: <input type="text" name="subject" maxlength="100" required></li>

    <li>Message: <textarea name="message" cols="40" rows="10" required></textarea></li>

    <li><ul class="errorlist"><li>Enter a valid email address.</li></ul>Sender: <input type="email" name="sender" value="invalid email address" required></li>

    <li>Cc myself: <input checked type="checkbox" name="cc_myself"></li>

    >>> print(f.as_p())

    <p><ul class="errorlist"><li>This field is required.</li></ul></p>

    <p>Subject: <input type="text" name="subject" maxlength="100" required></p>

    <p>Message: <textarea name="message" cols="40" rows="10" required></textarea></p>

    <p><ul class="errorlist"><li>Enter a valid email address.</li></ul></p>

    <p>Sender: <input type="email" name="sender" value="invalid email address" required></p>

    <p>Cc myself: <input checked type="checkbox" name="cc_myself"></p>

.. _ref-forms-error-list-format:

Customizing the error list format

---------------------------------

.. class:: ErrorList(initlist=None, error_class=None, renderer=None)

    By default, forms use ``django.forms.utils.ErrorList`` to format validation

    errors. ``ErrorList`` is a list like object where ``initlist`` is the

    list of errors. In addition this class has the following attributes and

    methods.

    .. attribute:: error_class

        The CSS classes to be used when rendering the error list. Any provided

        classes are added to the default ``errorlist`` class.

    .. attribute:: renderer

        .. versionadded:: 4.0

        Specifies the :doc:`renderer <renderers>` to use for ``ErrorList``.

        Defaults to ``None`` which means to use the default renderer

        specified by the :setting:`FORM_RENDERER` setting.

    .. attribute:: template_name

        .. versionadded:: 4.0

        The name of the template used when calling ``__str__`` or

        :meth:`render`. By default this is

        ``'django/forms/errors/list/default.html'`` which is a proxy for the

        ``'ul.html'`` template.

    .. attribute:: template_name_text

        .. versionadded:: 4.0

        The name of the template used when calling :meth:`.as_text`. By default

        this is ``'django/forms/errors/list/text.html'``. This template renders

        the errors as a list of bullet points.

    .. attribute:: template_name_ul

        .. versionadded:: 4.0

        The name of the template used when calling :meth:`.as_ul`. By default

        this is ``'django/forms/errors/list/ul.html'``. This template renders

        the errors in ``<li>`` tags with a wrapping ``<ul>`` with the CSS

        classes as defined by :attr:`.error_class`.

    .. method:: get_context()

        .. versionadded:: 4.0

        Return context for rendering of errors in a template.

        The available context is:

        * ``errors`` : A list of the errors.

        * ``error_class`` : A string of CSS classes.

    .. method:: render(template_name=None, context=None, renderer=None)

        .. versionadded:: 4.0

        The render method is called by ``__str__`` as well as by the

        :meth:`.as_ul` method.

        All arguments are optional and will default to:

        * ``template_name``: Value returned by :attr:`.template_name`

        * ``context``: Value returned by :meth:`.get_context`

        * ``renderer``: Value returned by :attr:`.renderer`

    .. method:: as_text()

        Renders the error list using the template defined by

        :attr:`.template_name_text`.

    .. method:: as_ul()

        Renders the error list using the template defined by

        :attr:`.template_name_ul`.

    If you'd like to customize the rendering of errors this can be achieved by

    overriding the :attr:`.template_name` attribute or more generally by

    overriding the default template, see also

    :ref:`overriding-built-in-form-templates`.

.. versionchanged:: 4.0

    Rendering of :class:`ErrorList` was moved to the template engine.

.. deprecated:: 4.0

    The ability to return a ``str`` when calling the ``__str__`` method is

    deprecated. Use the template engine instead which returns a ``SafeString``.

More granular output

====================

The ``as_p()``, ``as_ul()``, and ``as_table()`` methods are shortcuts --

they're not the only way a form object can be displayed.

.. class:: BoundField

   Used to display HTML or access attributes for a single field of a

   :class:`Form` instance.

   The ``__str__()`` method of this object displays the HTML for this field.

To retrieve a single ``BoundField``, use dictionary lookup syntax on your form

using the field's name as the key::

    >>> form = ContactForm()

    >>> print(form['subject'])

    <input id="id_subject" type="text" name="subject" maxlength="100" required>

To retrieve all ``BoundField`` objects, iterate the form::

    >>> form = ContactForm()

    >>> for boundfield in form: print(boundfield)

    <input id="id_subject" type="text" name="subject" maxlength="100" required>

    <input type="text" name="message" id="id_message" required>

    <input type="email" name="sender" id="id_sender" required>

    <input type="checkbox" name="cc_myself" id="id_cc_myself">

The field-specific output honors the form object's ``auto_id`` setting::

    >>> f = ContactForm(auto_id=False)

    >>> print(f['message'])

    <input type="text" name="message" required>

    >>> f = ContactForm(auto_id='id_%s')

    >>> print(f['message'])

    <input type="text" name="message" id="id_message" required>

Attributes of ``BoundField``

----------------------------

.. attribute:: BoundField.auto_id

    The HTML ID attribute for this ``BoundField``. Returns an empty string

    if :attr:`Form.auto_id` is ``False``.

.. attribute:: BoundField.data

    This property returns the data for this :class:`~django.forms.BoundField`

    extracted by the widget's :meth:`~django.forms.Widget.value_from_datadict`

    method, or ``None`` if it wasn't given::

        >>> unbound_form = ContactForm()

        >>> print(unbound_form['subject'].data)

        None

        >>> bound_form = ContactForm(data={'subject': 'My Subject'})

        >>> print(bound_form['subject'].data)

        My Subject

.. attribute:: BoundField.errors

    A :ref:`list-like object <ref-forms-error-list-format>` that is displayed

    as an HTML ``<ul class="errorlist">`` when printed::

        >>> data = {'subject': 'hi', 'message': '', 'sender': '', 'cc_myself': ''}

        >>> f = ContactForm(data, auto_id=False)

        >>> print(f['message'])

        <input type="text" name="message" required>

        >>> f['message'].errors

        ['This field is required.']

        >>> print(f['message'].errors)

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

        >>> f['subject'].errors

        []

        >>> print(f['subject'].errors)

        >>> str(f['subject'].errors)

        ''

.. attribute:: BoundField.field

    The form :class:`~django.forms.Field` instance from the form class that

    this :class:`~django.forms.BoundField` wraps.

.. attribute:: BoundField.form

    The :class:`~django.forms.Form` instance this :class:`~django.forms.BoundField`

    is bound to.

.. attribute:: BoundField.help_text

    The :attr:`~django.forms.Field.help_text` of the field.

.. attribute:: BoundField.html_name

    The name that will be used in the widget's HTML ``name`` attribute. It takes

    the form :attr:`~django.forms.Form.prefix` into account.

.. attribute:: BoundField.id_for_label

    Use this property to render the ID of this field. For example, if you are

    manually constructing a ``<label>`` in your template (despite the fact that

    :meth:`~BoundField.label_tag`/:meth:`~BoundField.legend_tag` will do this

    for you):

    .. code-block:: html+django

        <label for="{{ form.my_field.id_for_label }}">...</label>{{ my_field }}

    By default, this will be the field's name prefixed by ``id_``

    ("``id_my_field``" for the example above). You may modify the ID by setting

    :attr:`~django.forms.Widget.attrs` on the field's widget. For example,

    declaring a field like this::

        my_field = forms.CharField(widget=forms.TextInput(attrs={'id': 'myFIELD'}))

    and using the template above, would render something like:

    .. code-block:: html

        <label for="myFIELD">...</label><input id="myFIELD" type="text" name="my_field" required>

.. attribute:: BoundField.initial

    Use :attr:`BoundField.initial` to retrieve initial data for a form field.

    It retrieves the data from :attr:`Form.initial` if present, otherwise

    trying :attr:`Field.initial`. Callable values are evaluated. See

    :ref:`ref-forms-initial-form-values` for more examples.

    :attr:`BoundField.initial` caches its return value, which is useful

    especially when dealing with callables whose return values can change (e.g.

    ``datetime.now`` or ``uuid.uuid4``)::

        >>> from datetime import datetime

        >>> class DatedCommentForm(CommentForm):

        ...     created = forms.DateTimeField(initial=datetime.now)

        >>> f = DatedCommentForm()

        >>> f['created'].initial

        datetime.datetime(2021, 7, 27, 9, 5, 54)

        >>> f['created'].initial

        datetime.datetime(2021, 7, 27, 9, 5, 54)

    Using :attr:`BoundField.initial` is recommended over

    :meth:`~Form.get_initial_for_field()`.

.. attribute:: BoundField.is_hidden

    Returns ``True`` if this :class:`~django.forms.BoundField`'s widget is

    hidden.

.. attribute:: BoundField.label

    The :attr:`~django.forms.Field.label` of the field. This is used in

    :meth:`~BoundField.label_tag`/:meth:`~BoundField.legend_tag`.

.. attribute:: BoundField.name

    The name of this field in the form::

        >>> f = ContactForm()

        >>> print(f['subject'].name)

        subject

        >>> print(f['message'].name)

        message

.. attribute:: BoundField.use_fieldset

    .. versionadded:: 4.1

    Returns the value of this BoundField widget's ``use_fieldset`` attribute.

.. attribute:: BoundField.widget_type

    Returns the lowercased class name of the wrapped field's widget, with any

    trailing ``input`` or ``widget`` removed. This may be used when building

    forms where the layout is dependent upon the widget type. For example::

        {% for field in form %}

            {% if field.widget_type == 'checkbox' %}

                # render one way

            {% else %}

                # render another way

            {% endif %}

        {% endfor %}

Methods of ``BoundField``

-------------------------

.. method:: BoundField.as_hidden(attrs=None, **kwargs)

    Returns a string of HTML for representing this as an ``<input type="hidden">``.

    ``**kwargs`` are passed to :meth:`~django.forms.BoundField.as_widget`.

    This method is primarily used internally. You should use a widget instead.

.. method:: BoundField.as_widget(widget=None, attrs=None, only_initial=False)

    Renders the field by rendering the passed widget, adding any HTML

    attributes passed as ``attrs``.  If no widget is specified, then the

    field's default widget will be used.

    ``only_initial`` is used by Django internals and should not be set

    explicitly.

.. method:: BoundField.css_classes(extra_classes=None)

    When you use Django's rendering shortcuts, CSS classes are used to

    indicate required form fields or fields that contain errors. If you're

    manually rendering a form, you can access these CSS classes using the

    ``css_classes`` method::

        >>> f = ContactForm(data={'message': ''})

        >>> f['message'].css_classes()

        'required'

    If you want to provide some additional classes in addition to the

    error and required classes that may be required, you can provide

    those classes as an argument::

        >>> f = ContactForm(data={'message': ''})

        >>> f['message'].css_classes('foo bar')

        'foo bar required'

.. method:: BoundField.label_tag(contents=None, attrs=None, label_suffix=None, tag=None)

    Renders a label tag for the form field using the template specified by

    :attr:`.Form.template_name_label`.

    The available context is:

    * ``field``: This instance of the :class:`BoundField`.

    * ``contents``: By default a concatenated string of

      :attr:`BoundField.label` and :attr:`Form.label_suffix` (or

      :attr:`Field.label_suffix`, if set). This can be overridden by the

      ``contents`` and ``label_suffix`` arguments.

    * ``attrs``: A ``dict`` containing ``for``,

      :attr:`Form.required_css_class`, and ``id``. ``id`` is generated by the

      field's widget ``attrs`` or :attr:`BoundField.auto_id`. Additional

      attributes can be provided by the ``attrs`` argument.

    * ``use_tag``: A boolean which is ``True`` if the label has an ``id``.

      If ``False`` the default template omits the ``tag``.

    * ``tag``: An optional string to customize the tag, defaults to ``label``.

    .. tip::

        In your template ``field`` is the instance of the ``BoundField``.

        Therefore ``field.field`` accesses :attr:`BoundField.field` being

        the field you declare, e.g. ``forms.CharField``.

    To separately render the label tag of a form field, you can call its

    ``label_tag()`` method::

        >>> f = ContactForm(data={'message': ''})

        >>> print(f['message'].label_tag())

        <label for="id_message">Message:</label>

    If you'd like to customize the rendering this can be achieved by overriding

    the :attr:`.Form.template_name_label` attribute or more generally by

    overriding the default template, see also

    :ref:`overriding-built-in-form-templates`.

    .. versionchanged:: 4.0

        The label is now rendered using the template engine.

    .. versionchanged:: 4.1

        The ``tag`` argument was added.

.. method:: BoundField.legend_tag(contents=None, attrs=None, label_suffix=None)

    .. versionadded:: 4.1

    Calls :meth:`.label_tag` with ``tag='legend'`` to render the label with

    ``<legend>`` tags. This is useful when rendering radio and multiple

    checkbox widgets where ``<legend>`` may be more appropriate than a

    ``<label>``.

.. method:: BoundField.value()

    Use this method to render the raw value of this field as it would be rendered

    by a ``Widget``::

        >>> initial = {'subject': 'welcome'}

        >>> unbound_form = ContactForm(initial=initial)

        >>> bound_form = ContactForm(data={'subject': 'hi'}, initial=initial)

        >>> print(unbound_form['subject'].value())

        welcome

        >>> print(bound_form['subject'].value())

        hi

Customizing ``BoundField``

==========================

If you need to access some additional information about a form field in a

template and using a subclass of :class:`~django.forms.Field` isn't

sufficient, consider also customizing :class:`~django.forms.BoundField`.

A custom form field can override ``get_bound_field()``:

.. method:: Field.get_bound_field(form, field_name)

    Takes an instance of :class:`~django.forms.Form` and the name of the field.

    The return value will be used when accessing the field in a template. Most

    likely it will be an instance of a subclass of

    :class:`~django.forms.BoundField`.

If you have a ``GPSCoordinatesField``, for example, and want to be able to

access additional information about the coordinates in a template, this could

be implemented as follows::

    class GPSCoordinatesBoundField(BoundField):

        @property

        def country(self):

            """

            Return the country the coordinates lie in or None if it can't be

            determined.

            """

            value = self.value()

            if value:

                return get_country_from_coordinates(value)

            else:

                return None

    class GPSCoordinatesField(Field):

        def get_bound_field(self, form, field_name):

            return GPSCoordinatesBoundField(form, self, field_name)

Now you can access the country in a template with

``{{ form.coordinates.country }}``.

.. _binding-uploaded-files:

Binding uploaded files to a form

================================

Dealing with forms that have ``FileField`` and ``ImageField`` fields

is a little more complicated than a normal form.

Firstly, in order to upload files, you'll need to make sure that your

``<form>`` element correctly defines the ``enctype`` as

``"multipart/form-data"``::

  <form enctype="multipart/form-data" method="post" action="/foo/">

Secondly, when you use the form, you need to bind the file data. File

data is handled separately to normal form data, so when your form

contains a ``FileField`` and ``ImageField``, you will need to specify

a second argument when you bind your form. So if we extend our

ContactForm to include an ``ImageField`` called ``mugshot``, we

need to bind the file data containing the mugshot image::

    # Bound form with an image field

    >>> from django.core.files.uploadedfile import SimpleUploadedFile

    >>> data = {'subject': 'hello',

    ...         'message': 'Hi there',

    ...         'sender': '[email protected]',

    ...         'cc_myself': True}

    >>> file_data = {'mugshot': SimpleUploadedFile('face.jpg', <file data>)}

    >>> f = ContactFormWithMugshot(data, file_data)

In practice, you will usually specify ``request.FILES`` as the source

of file data (just like you use ``request.POST`` as the source of

form data)::

    # Bound form with an image field, data from the request

    >>> f = ContactFormWithMugshot(request.POST, request.FILES)

Constructing an unbound form is the same as always -- omit both form data *and*

file data::

    # Unbound form with an image field

    >>> f = ContactFormWithMugshot()

Testing for multipart forms

---------------------------

.. method:: Form.is_multipart()

If you're writing reusable views or templates, you may not know ahead of time

whether your form is a multipart form or not. The ``is_multipart()`` method

tells you whether the form requires multipart encoding for submission::

    >>> f = ContactFormWithMugshot()

    >>> f.is_multipart()

    True

Here's an example of how you might use this in a template::

    {% if form.is_multipart %}

        <form enctype="multipart/form-data" method="post" action="/foo/">

    {% else %}

        <form method="post" action="/foo/">

    {% endif %}

    {{ form }}

    </form>

Subclassing forms

=================

If you have multiple ``Form`` classes that share fields, you can use

subclassing to remove redundancy.

When you subclass a custom ``Form`` class, the resulting subclass will

include all fields of the parent class(es), followed by the fields you define

in the subclass.

In this example, ``ContactFormWithPriority`` contains all the fields from

``ContactForm``, plus an additional field, ``priority``. The ``ContactForm``

fields are ordered first::

    >>> class ContactFormWithPriority(ContactForm):

    ...     priority = forms.CharField()

    >>> f = ContactFormWithPriority(auto_id=False)

    >>> print(f.as_div())

    <div>Subject:<input type="text" name="subject" maxlength="100" required></div>

    <div>Message:<textarea name="message" cols="40" rows="10" required></textarea></div>

    <div>Sender:<input type="email" name="sender" required></div>

    <div>Cc myself:<input type="checkbox" name="cc_myself"></div>

    <div>Priority:<input type="text" name="priority" required></div>

It's possible to subclass multiple forms, treating forms as mixins. In this

example, ``BeatleForm`` subclasses both ``PersonForm`` and ``InstrumentForm``

(in that order), and its field list includes the fields from the parent

classes::

    >>> from django import forms

    >>> class PersonForm(forms.Form):

    ...     first_name = forms.CharField()

    ...     last_name = forms.CharField()

    >>> class InstrumentForm(forms.Form):

    ...     instrument = forms.CharField()

    >>> class BeatleForm(InstrumentForm, PersonForm):

    ...     haircut_type = forms.CharField()

    >>> b = BeatleForm(auto_id=False)

    >>> print(b.as_div())

    <div>First name:<input type="text" name="first_name" required></div>

    <div>Last name:<input type="text" name="last_name" required></div>

    <div>Instrument:<input type="text" name="instrument" required></div>

    <div>Haircut type:<input type="text" name="haircut_type" required></div>

It's possible to declaratively remove a ``Field`` inherited from a parent class

by setting the name of the field to ``None`` on the subclass. For example::

    >>> from django import forms

    >>> class ParentForm(forms.Form):

    ...     name = forms.CharField()

    ...     age = forms.IntegerField()

    >>> class ChildForm(ParentForm):

    ...     name = None

    >>> list(ChildForm().fields)

    ['age']

.. _form-prefix:

Prefixes for forms

==================

.. attribute:: Form.prefix

You can put several Django forms inside one ``<form>`` tag. To give each

``Form`` its own namespace, use the ``prefix`` keyword argument::

    >>> mother = PersonForm(prefix="mother")

    >>> father = PersonForm(prefix="father")

    >>> print(mother.as_div())

    <div><label for="id_mother-first_name">First name:</label><input type="text" name="mother-first_name" required id="id_mother-first_name"></div>

    <div><label for="id_mother-last_name">Last name:</label><input type="text" name="mother-last_name" required id="id_mother-last_name"></div>

    >>> print(father.as_div())

    <div><label for="id_father-first_name">First name:</label><input type="text" name="father-first_name" required id="id_father-first_name"></div>

    <div><label for="id_father-last_name">Last name:</label><input type="text" name="father-last_name" required id="id_father-last_name"></div>

The prefix can also be specified on the form class::

    >>> class PersonForm(forms.Form):

    ...     ...

    ...     prefix = 'person'