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The Forms API¶

About this document

This document covers the gritty details of Django’s forms API. You should read the introduction to working with forms first.

Bound and unbound forms¶

A 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 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 Form class constructor:

>>> data = {
...     "subject": "hello",
...     "message": "Hi there",
...     "sender": "foo@example.com",
...     "cc_myself": True,
... }
>>> f = ContactForm(data)

In this dictionary, the keys are the field names, which correspond to the attributes in your 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 Field, as we’ll see in a moment.

Form.is_bound¶

If you need to distinguish between bound and unbound form instances at runtime, check the value of the form’s 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 Form instance and want to change the data somehow, or if you want to bind an unbound Form instance to some data, create another Form instance. There is no way to change data in a Form instance. Once a Form instance has been created, you should consider its data immutable, whether it has data or not.

Using forms to validate data¶

Form.clean()¶

Implement a clean() method on your Form when you must add custom validation for fields that are interdependent. See Cleaning and validating fields that depend on each other for example usage.

Form.is_valid()¶

The primary task of a Form object is to validate data. With a bound Form instance, call the is_valid() method to run validation and return a boolean designating whether the data was valid:

>>> data = {
...     "subject": "hello",
...     "message": "Hi there",
...     "sender": "foo@example.com",
...     "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

Form.errors¶

Access the 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 errors without having to call is_valid() first. The form’s data will be validated the first time either you call is_valid() or access errors.

The validation routines will only get called once, regardless of how many times you access errors or call is_valid(). This means that if validation has side effects, those side effects will only be triggered once.

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, 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.

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.

Form.errors.get_json_data(escape_html=False)¶

Returns the errors as a dictionary suitable for serializing to JSON. 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 Form.errors.as_json().

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 Form.non_field_errors().

The error argument can be a string, or preferably an instance of ValidationError. See Raising ValidationError for best practices when defining form errors.

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

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 NON_FIELD_ERRORS as the field parameter.

Form.non_field_errors()¶

This method returns the list of errors from Form.errors that aren’t associated with a particular field. This includes ValidationErrors that are raised in Form.clean() and errors added using Form.add_error(None, "...").

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
{}

Initial form values¶

Form.initial¶

Use 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 initial argument to a 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 Field defines initial and you include 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>

Form.get_initial_for_field(field, field_name)¶

Returns the initial data for a form field. It retrieves the data from Form.initial if present, otherwise trying Field.initial. Callable values are evaluated.

It is recommended to use BoundField.initial over get_initial_for_field() because BoundField.initial has a simpler interface. Also, unlike get_initial_for_field(), 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¶

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': 'foo@example.com',
...         '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 initial or False otherwise. The result is computed by calling Field.has_changed() for each field in the form.

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 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¶

Form.fields¶

You can access the fields of 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 BoundField of 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¶

Form.cleaned_data¶

Each field in a 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, 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 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": "foo@example.com",
...     "cc_myself": True,
... }
>>> f = ContactForm(data)
>>> f.is_valid()
True
>>> f.cleaned_data
{'cc_myself': True, 'message': 'Hi there', 'sender': 'foo@example.com', '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": "foo@example.com",
...     "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': 'foo@example.com', '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 CharFields 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 Form and field validation.

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": "foo@example.com",
...     "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="foo@example.com" 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`¶

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 form_template_name. You may set it as a string template name in order to override that for a particular form class.

In older versions template_name defaulted to the string value 'django/forms/default.html'.

`render()`¶

Form.render(template_name=None, context=None, renderer=None)¶

The render method is called by __str__ as well as the Form.as_table(), Form.as_p(), and Form.as_ul() methods. All arguments are optional and default to:

template_name: Form.template_name
context: Value returned by Form.get_context()
renderer: Value returned by Form.default_renderer

By passing template_name you can customize the template used for just a single call.

`get_context()`¶

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`¶

Form.template_name_label¶

The template used to render a field’s <label>, used when calling BoundField.label_tag()/legend_tag(). Can be changed per form by overriding this attribute or more generally by overriding the default template, see also 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 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 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()`¶

Form.template_name_div¶

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

Form.as_div()¶

as_div() renders the form as a series of <div> elements, with each <div> containing one field, such as:

>>> f = ContactForm()
>>> f.as_div()

… gives HTML like:

<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()`¶

Form.template_name_p¶

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

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()`¶

Form.template_name_ul¶

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

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()`¶

Form.template_name_table¶

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

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>

Styling required or erroneous form rows¶

Form.error_css_class¶

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 Form class has a couple of hooks you can use to add class attributes to required rows or to rows with errors: set the Form.error_css_class and/or 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>

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

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'.

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 label_suffix. This will take precedence over Form.label_suffix. The suffix can also be overridden at runtime using the label_suffix parameter to label_tag()/ legend_tag().

Form.use_required_attribute¶

When set to True (the default), required form fields will have the required HTML attribute.

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¶

Form.default_renderer¶

Specifies the renderer to use for the form. Defaults to None which means to use the default renderer specified by the 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:

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 Form to override the field order. If a Form defines field_order and you include field_order when instantiating the Form, then the latter field_order will have precedence.

Form.order_fields(field_order)¶

You may rearrange the fields any time using order_fields() with a list of field names as in 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>

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.

error_class¶: The CSS classes to be used when rendering the error list. Any provided classes are added to the default errorlist class.

renderer¶: Specifies the renderer to use for ErrorList. Defaults to None which means to use the default renderer specified by the FORM_RENDERER setting.

template_name¶: The name of the template used when calling __str__ or render(). By default this is 'django/forms/errors/list/default.html' which is a proxy for the 'ul.html' template.

template_name_text¶: The name of the template used when calling as_text(). By default this is 'django/forms/errors/list/text.html'. This template renders the errors as a list of bullet points.

template_name_ul¶: The name of the template used when calling 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 error_class.

get_context()¶

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.

render(template_name=None, context=None, renderer=None)¶

The render method is called by __str__ as well as by the as_ul() method.

All arguments are optional and will default to:

template_name: Value returned by template_name
context: Value returned by get_context()
renderer: Value returned by renderer

as_text()¶: Renders the error list using the template defined by template_name_text.

as_ul()¶: Renders the error list using the template defined by template_name_ul.

If you’d like to customize the rendering of errors this can be achieved by overriding the template_name attribute or more generally by overriding the default template, see also Overriding built-in form templates.

Deprecated since version 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 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`¶

BoundField.auto_id¶: The HTML ID attribute for this BoundField. Returns an empty string if Form.auto_id is False.

BoundField.data¶

This property returns the data for this BoundField extracted by the widget’s 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

BoundField.errors¶

A list-like object 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)
''

BoundField.field¶: The form Field instance from the form class that this BoundField wraps.

BoundField.form¶: The Form instance this BoundField is bound to.

BoundField.help_text¶: The help_text of the field.

BoundField.html_name¶: The name that will be used in the widget’s HTML name attribute. It takes the form prefix into account.

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 label_tag()/legend_tag() will do this for you):

<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 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:

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

BoundField.initial¶

Use BoundField.initial to retrieve initial data for a form field. It retrieves the data from Form.initial if present, otherwise trying Field.initial. Callable values are evaluated. See Initial form values for more examples.

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 BoundField.initial is recommended over get_initial_for_field().

BoundField.is_hidden¶: Returns True if this BoundField’s widget is hidden.

BoundField.label¶: The label of the field. This is used in label_tag()/legend_tag().

BoundField.name¶

The name of this field in the form:

>>> f = ContactForm()
>>> print(f["subject"].name)
subject
>>> print(f["message"].name)
message

BoundField.use_fieldset¶: Returns the value of this BoundField widget’s use_fieldset 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`¶

BoundField.as_hidden(attrs=None, **kwargs)¶

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

**kwargs are passed to as_widget().

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

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.

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'

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 Form.template_name_label.

The available context is:

field: This instance of the BoundField.
contents: By default a concatenated string of BoundField.label and Form.label_suffix (or Field.label_suffix, if set). This can be overridden by the contents and label_suffix arguments.
attrs: A dict containing for, Form.required_css_class, and id. id is generated by the field’s widget attrs or 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 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 Form.template_name_label attribute or more generally by overriding the default template, see also Overriding built-in form templates.

The tag argument was added.

BoundField.legend_tag(contents=None, attrs=None, label_suffix=None)¶: Calls 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>.

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 Field isn’t sufficient, consider also customizing BoundField.

A custom form field can override get_bound_field():

Field.get_bound_field(form, field_name)¶: Takes an instance of 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 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 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": "foo@example.com",
...     "cc_myself": True,
... }
>>> file_data = {"mugshot": SimpleUploadedFile("face.jpg", b"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¶

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']

Prefixes for forms¶

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"
...

« previous | up | next »

Django 4.2.8 documentation

The Forms API¶

Bound and unbound forms¶

Using forms to validate data¶

Behavior of unbound forms¶

Initial form values¶

Checking which form data has changed¶

Accessing the fields from the form¶

Accessing “clean” data¶

Outputting forms as HTML¶

Default rendering¶

`template_name`¶

`render()`¶

`get_context()`¶

`template_name_label`¶

Output styles¶

`as_div()`¶

`as_p()`¶

`as_ul()`¶

`as_table()`¶

Styling required or erroneous form rows¶

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

Configuring the rendering of a form’s widgets¶

Notes on field ordering¶

How errors are displayed¶

Customizing the error list format¶

More granular output¶

Attributes of `BoundField`¶

Methods of `BoundField`¶

Customizing `BoundField`¶

Binding uploaded files to a form¶

Testing for multipart forms¶

Subclassing forms¶

Prefixes for forms¶

Table of Contents

Previous topic

Next topic

This Page

Last update:

Django 4.2.8 documentation

The Forms API¶

Bound and unbound forms¶

Using forms to validate data¶

Behavior of unbound forms¶

Initial form values¶

Checking which form data has changed¶

Accessing the fields from the form¶

Accessing “clean” data¶

Outputting forms as HTML¶

Default rendering¶

template_name¶

render()¶

get_context()¶

template_name_label¶

Output styles¶

as_div()¶

as_p()¶

as_ul()¶

as_table()¶

Styling required or erroneous form rows¶

Configuring form elements’ HTML id attributes and <label> tags¶

Configuring the rendering of a form’s widgets¶

Notes on field ordering¶

How errors are displayed¶

Customizing the error list format¶

More granular output¶

Attributes of BoundField¶

Methods of BoundField¶

Customizing BoundField¶

Binding uploaded files to a form¶

Testing for multipart forms¶

Subclassing forms¶

Prefixes for forms¶

Last update:

`template_name`¶

`render()`¶

`get_context()`¶

`template_name_label`¶

`as_div()`¶

`as_p()`¶

`as_ul()`¶

`as_table()`¶

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

Attributes of `BoundField`¶

Methods of `BoundField`¶

Customizing `BoundField`¶