Form fields¶
When you create a Form
class, the most important part is defining the
fields of the form. Each field has custom validation logic, along with a few
other hooks.
Although the primary way you’ll use Field
classes is in Form
classes,
you can also instantiate them and use them directly to get a better idea of
how they work. Each Field
instance has a clean()
method, which takes
a single argument and either raises a
django.core.exceptions.ValidationError
exception or returns the clean
value:
>>> from django import forms
>>> f = forms.EmailField()
>>> f.clean('foo@example.com')
'foo@example.com'
>>> f.clean('invalid email address')
Traceback (most recent call last):
...
ValidationError: ['Enter a valid email address.']
Core field arguments¶
Each Field
class constructor takes at least these arguments. Some
Field
classes take additional, field-specific arguments, but the following
should always be accepted:
required
¶
-
Field.
required
¶
By default, each Field
class assumes the value is required, so if you pass
an empty value – either None
or the empty string (""
) – then
clean()
will raise a ValidationError
exception:
>>> from django import forms
>>> f = forms.CharField()
>>> f.clean('foo')
'foo'
>>> f.clean('')
Traceback (most recent call last):
...
ValidationError: ['This field is required.']
>>> f.clean(None)
Traceback (most recent call last):
...
ValidationError: ['This field is required.']
>>> f.clean(' ')
' '
>>> f.clean(0)
'0'
>>> f.clean(True)
'True'
>>> f.clean(False)
'False'
To specify that a field is not required, pass required=False
to the
Field
constructor:
>>> f = forms.CharField(required=False)
>>> f.clean('foo')
'foo'
>>> f.clean('')
''
>>> f.clean(None)
''
>>> f.clean(0)
'0'
>>> f.clean(True)
'True'
>>> f.clean(False)
'False'
If a Field
has required=False
and you pass clean()
an empty value,
then clean()
will return a normalized empty value rather than raising
ValidationError
. For CharField
, this will return
empty_value
which defaults to an empty string. For other
Field
classes, it might be None
. (This varies from field to field.)
Widgets of required form fields have the required
HTML attribute. Set the
Form.use_required_attribute
attribute to False
to disable it. The
required
attribute isn’t included on forms of formsets because the browser
validation may not be correct when adding and deleting formsets.
label
¶
-
Field.
label
¶
The label
argument lets you specify the “human-friendly” label for this
field. This is used when the Field
is displayed in a Form
.
As explained in “Outputting forms as HTML” above, the default label for a
Field
is generated from the field name by converting all underscores to
spaces and upper-casing the first letter. Specify label
if that default
behavior doesn’t result in an adequate label.
Here’s a full example Form
that implements label
for two of its fields.
We’ve specified auto_id=False
to simplify the output:
>>> from django import forms
>>> class CommentForm(forms.Form):
... name = forms.CharField(label='Your name')
... url = forms.URLField(label='Your website', required=False)
... comment = forms.CharField()
>>> f = CommentForm(auto_id=False)
>>> print(f)
<tr><th>Your name:</th><td><input type="text" name="name" required></td></tr>
<tr><th>Your website:</th><td><input type="url" name="url"></td></tr>
<tr><th>Comment:</th><td><input type="text" name="comment" required></td></tr>
label_suffix
¶
-
Field.
label_suffix
¶
The label_suffix
argument lets you override the form’s
label_suffix
on a per-field basis:
>>> class ContactForm(forms.Form):
... age = forms.IntegerField()
... nationality = forms.CharField()
... captcha_answer = forms.IntegerField(label='2 + 2', label_suffix=' =')
>>> f = ContactForm(label_suffix='?')
>>> print(f.as_p())
<p><label for="id_age">Age?</label> <input id="id_age" name="age" type="number" required></p>
<p><label for="id_nationality">Nationality?</label> <input id="id_nationality" name="nationality" type="text" required></p>
<p><label for="id_captcha_answer">2 + 2 =</label> <input id="id_captcha_answer" name="captcha_answer" type="number" required></p>
initial
¶
-
Field.
initial
¶
The initial
argument lets you specify the initial value to use when
rendering this Field
in an unbound Form
.
To specify dynamic initial data, see the Form.initial
parameter.
The use-case for this is when you want to display an “empty” form in which a field is initialized to a particular value. For example:
>>> from django import forms
>>> class CommentForm(forms.Form):
... name = forms.CharField(initial='Your name')
... url = forms.URLField(initial='http://')
... comment = forms.CharField()
>>> f = CommentForm(auto_id=False)
>>> print(f)
<tr><th>Name:</th><td><input type="text" name="name" value="Your name" required></td></tr>
<tr><th>Url:</th><td><input type="url" name="url" value="http://" required></td></tr>
<tr><th>Comment:</th><td><input type="text" name="comment" required></td></tr>
You may be thinking, why not just pass a dictionary of the initial values as data when displaying the form? Well, if you do that, you’ll trigger validation, and the HTML output will include any validation errors:
>>> class CommentForm(forms.Form):
... name = forms.CharField()
... url = forms.URLField()
... comment = forms.CharField()
>>> default_data = {'name': 'Your name', 'url': 'http://'}
>>> f = CommentForm(default_data, auto_id=False)
>>> print(f)
<tr><th>Name:</th><td><input type="text" name="name" value="Your name" required></td></tr>
<tr><th>Url:</th><td><ul class="errorlist"><li>Enter a valid URL.</li></ul><input type="url" name="url" value="http://" required></td></tr>
<tr><th>Comment:</th><td><ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="comment" required></td></tr>
This is why initial
values are only displayed for unbound forms. For bound
forms, the HTML output will use the bound data.
Also note that initial
values are not used as “fallback” data in
validation if a particular field’s value is not given. initial
values are
only intended for initial form display:
>>> class CommentForm(forms.Form):
... name = forms.CharField(initial='Your name')
... url = forms.URLField(initial='http://')
... comment = forms.CharField()
>>> data = {'name': '', 'url': '', 'comment': 'Foo'}
>>> f = CommentForm(data)
>>> f.is_valid()
False
# The form does *not* fall back to using the initial values.
>>> f.errors
{'url': ['This field is required.'], 'name': ['This field is required.']}
Instead of a constant, you can also pass any callable:
>>> import datetime
>>> class DateForm(forms.Form):
... day = forms.DateField(initial=datetime.date.today)
>>> print(DateForm())
<tr><th>Day:</th><td><input type="text" name="day" value="12/23/2008" required><td></tr>
The callable will be evaluated only when the unbound form is displayed, not when it is defined.
widget
¶
-
Field.
widget
¶
The widget
argument lets you specify a Widget
class to use when
rendering this Field
. See Widgets for more information.
help_text
¶
-
Field.
help_text
¶
The help_text
argument lets you specify descriptive text for this
Field
. If you provide help_text
, it will be displayed next to the
Field
when the Field
is rendered by one of the convenience Form
methods (e.g., as_ul()
).
Like the model field’s help_text
, this value
isn’t HTML-escaped in automatically-generated forms.
Here’s a full example Form
that implements help_text
for two of its
fields. We’ve specified auto_id=False
to simplify the output:
>>> from django import forms
>>> class HelpTextContactForm(forms.Form):
... subject = forms.CharField(max_length=100, help_text='100 characters max.')
... message = forms.CharField()
... sender = forms.EmailField(help_text='A valid email address, please.')
... cc_myself = forms.BooleanField(required=False)
>>> f = HelpTextContactForm(auto_id=False)
>>> print(f.as_table())
<tr><th>Subject:</th><td><input type="text" name="subject" maxlength="100" required><br><span class="helptext">100 characters max.</span></td></tr>
<tr><th>Message:</th><td><input type="text" name="message" required></td></tr>
<tr><th>Sender:</th><td><input type="email" name="sender" required><br>A valid email address, please.</td></tr>
<tr><th>Cc myself:</th><td><input type="checkbox" name="cc_myself"></td></tr>
>>> print(f.as_ul()))
<li>Subject: <input type="text" name="subject" maxlength="100" required> <span class="helptext">100 characters max.</span></li>
<li>Message: <input type="text" name="message" required></li>
<li>Sender: <input type="email" name="sender" required> A valid email address, please.</li>
<li>Cc myself: <input type="checkbox" name="cc_myself"></li>
>>> print(f.as_p())
<p>Subject: <input type="text" name="subject" maxlength="100" required> <span class="helptext">100 characters max.</span></p>
<p>Message: <input type="text" name="message" required></p>
<p>Sender: <input type="email" name="sender" required> A valid email address, please.</p>
<p>Cc myself: <input type="checkbox" name="cc_myself"></p>
error_messages
¶
-
Field.
error_messages
¶
The error_messages
argument lets you override the default messages that the
field will raise. Pass in a dictionary with keys matching the error messages you
want to override. For example, here is the default error message:
>>> from django import forms
>>> generic = forms.CharField()
>>> generic.clean('')
Traceback (most recent call last):
...
ValidationError: ['This field is required.']
And here is a custom error message:
>>> name = forms.CharField(error_messages={'required': 'Please enter your name'})
>>> name.clean('')
Traceback (most recent call last):
...
ValidationError: ['Please enter your name']
In the built-in Field classes section below, each Field
defines the
error message keys it uses.
validators
¶
-
Field.
validators
¶
The validators
argument lets you provide a list of validation functions
for this field.
See the validators documentation for more information.
localize
¶
-
Field.
localize
¶
The localize
argument enables the localization of form data input, as well
as the rendered output.
See the format localization documentation for more information.
disabled
¶
-
Field.
disabled
¶
The disabled
boolean argument, when set to True
, disables a form field
using the disabled
HTML attribute so that it won’t be editable by users.
Even if a user tampers with the field’s value submitted to the server, it will
be ignored in favor of the value from the form’s initial data.
Checking if the field data has changed¶
has_changed()
¶
The has_changed()
method is used to determine if the field value has changed
from the initial value. Returns True
or False
.
See the Form.has_changed()
documentation for more information.
Built-in Field
classes¶
Naturally, the forms
library comes with a set of Field
classes that
represent common validation needs. This section documents each built-in field.
For each field, we describe the default widget used if you don’t specify
widget
. We also specify the value returned when you provide an empty value
(see the section on required
above to understand what that means).
BooleanField
¶
-
class
BooleanField
(**kwargs)[source]¶ - Default widget:
CheckboxInput
- Empty value:
False
- Normalizes to: A Python
True
orFalse
value. - Validates that the value is
True
(e.g. the check box is checked) if the field hasrequired=True
. - Error message keys:
required
Note
Since all
Field
subclasses haverequired=True
by default, the validation condition here is important. If you want to include a boolean in your form that can be eitherTrue
orFalse
(e.g. a checked or unchecked checkbox), you must remember to pass inrequired=False
when creating theBooleanField
.- Default widget:
CharField
¶
-
class
CharField
(**kwargs)[source]¶ - Default widget:
TextInput
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A string.
- Uses
MaxLengthValidator
andMinLengthValidator
ifmax_length
andmin_length
are provided. Otherwise, all inputs are valid. - Error message keys:
required
,max_length
,min_length
Has four optional arguments for validation:
-
max_length
¶
-
min_length
¶ If provided, these arguments ensure that the string is at most or at least the given length.
-
strip
¶ If
True
(default), the value will be stripped of leading and trailing whitespace.
-
empty_value
¶ The value to use to represent “empty”. Defaults to an empty string.
- Default widget:
ChoiceField
¶
-
class
ChoiceField
(**kwargs)[source]¶ - Default widget:
Select
- Empty value:
''
(an empty string) - Normalizes to: A string.
- Validates that the given value exists in the list of choices.
- Error message keys:
required
,invalid_choice
The
invalid_choice
error message may contain%(value)s
, which will be replaced with the selected choice.Takes one extra argument:
-
choices
¶ Either an iterable of 2-tuples to use as choices for this field, enumeration choices, or a callable that returns such an iterable. This argument accepts the same formats as the
choices
argument to a model field. See the model field reference documentation on choices for more details. If the argument is a callable, it is evaluated each time the field’s form is initialized, in addition to during rendering. Defaults to an empty list.
- Default widget:
TypedChoiceField
¶
-
class
TypedChoiceField
(**kwargs)[source]¶ Just like a
ChoiceField
, exceptTypedChoiceField
takes two extra arguments,coerce
andempty_value
.- Default widget:
Select
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A value of the type provided by the
coerce
argument. - Validates that the given value exists in the list of choices and can be coerced.
- Error message keys:
required
,invalid_choice
Takes extra arguments:
-
coerce
¶ A function that takes one argument and returns a coerced value. Examples include the built-in
int
,float
,bool
and other types. Defaults to an identity function. Note that coercion happens after input validation, so it is possible to coerce to a value not present inchoices
.
-
empty_value
¶ The value to use to represent “empty.” Defaults to the empty string;
None
is another common choice here. Note that this value will not be coerced by the function given in thecoerce
argument, so choose it accordingly.
- Default widget:
DateField
¶
-
class
DateField
(**kwargs)[source]¶ - Default widget:
DateInput
- Empty value:
None
- Normalizes to: A Python
datetime.date
object. - Validates that the given value is either a
datetime.date
,datetime.datetime
or string formatted in a particular date format. - Error message keys:
required
,invalid
Takes one optional argument:
-
input_formats
¶ A list of formats used to attempt to convert a string to a valid
datetime.date
object.
If no
input_formats
argument is provided, the default input formats are taken fromDATE_INPUT_FORMATS
ifUSE_L10N
isFalse
, or from the active locale formatDATE_INPUT_FORMATS
key if localization is enabled. See also format localization.- Default widget:
DateTimeField
¶
-
class
DateTimeField
(**kwargs)[source]¶ - Default widget:
DateTimeInput
- Empty value:
None
- Normalizes to: A Python
datetime.datetime
object. - Validates that the given value is either a
datetime.datetime
,datetime.date
or string formatted in a particular datetime format. - Error message keys:
required
,invalid
Takes one optional argument:
-
input_formats
¶ A list of formats used to attempt to convert a string to a valid
datetime.datetime
object, in addition to ISO 8601 formats.
The field always accepts strings in ISO 8601 formatted dates or similar recognized by
parse_datetime()
. Some examples are:* '2006-10-25 14:30:59' * '2006-10-25T14:30:59' * '2006-10-25 14:30' * '2006-10-25T14:30' * '2006-10-25T14:30Z' * '2006-10-25T14:30+02:00' * '2006-10-25'
If no
input_formats
argument is provided, the default input formats are taken fromDATETIME_INPUT_FORMATS
andDATE_INPUT_FORMATS
ifUSE_L10N
isFalse
, or from the active locale formatDATETIME_INPUT_FORMATS
andDATE_INPUT_FORMATS
keys if localization is enabled. See also format localization.Changed in Django 3.1:Support for ISO 8601 date string parsing (including optional timezone) was added.
The fallback on
DATE_INPUT_FORMATS
in the defaultinput_formats
was added.- Default widget:
DecimalField
¶
-
class
DecimalField
(**kwargs)[source]¶ - Default widget:
NumberInput
whenField.localize
isFalse
, elseTextInput
. - Empty value:
None
- Normalizes to: A Python
decimal
. - Validates that the given value is a decimal. Uses
MaxValueValidator
andMinValueValidator
ifmax_value
andmin_value
are provided. Leading and trailing whitespace is ignored. - Error message keys:
required
,invalid
,max_value
,min_value
,max_digits
,max_decimal_places
,max_whole_digits
The
max_value
andmin_value
error messages may contain%(limit_value)s
, which will be substituted by the appropriate limit. Similarly, themax_digits
,max_decimal_places
andmax_whole_digits
error messages may contain%(max)s
.Takes four optional arguments:
-
max_value
¶
-
min_value
¶ These control the range of values permitted in the field, and should be given as
decimal.Decimal
values.
-
max_digits
¶ The maximum number of digits (those before the decimal point plus those after the decimal point, with leading zeros stripped) permitted in the value.
-
decimal_places
¶ The maximum number of decimal places permitted.
- Default widget:
DurationField
¶
-
class
DurationField
(**kwargs)[source]¶ - Default widget:
TextInput
- Empty value:
None
- Normalizes to: A Python
timedelta
. - Validates that the given value is a string which can be converted into a
timedelta
. The value must be betweendatetime.timedelta.min
anddatetime.timedelta.max
. - Error message keys:
required
,invalid
,overflow
.
Accepts any format understood by
parse_duration()
.- Default widget:
EmailField
¶
-
class
EmailField
(**kwargs)[source]¶ - Default widget:
EmailInput
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A string.
- Uses
EmailValidator
to validate that the given value is a valid email address, using a moderately complex regular expression. - Error message keys:
required
,invalid
Has three optional arguments
max_length
,min_length
, andempty_value
which work just as they do forCharField
. Themax_length
argument defaults to 320 (see RFC 3696#section-3).Changed in Django 3.2.20:The default value for
max_length
was changed to 320 characters.- Default widget:
FileField
¶
-
class
FileField
(**kwargs)[source]¶ - Default widget:
ClearableFileInput
- Empty value:
None
- Normalizes to: An
UploadedFile
object that wraps the file content and file name into a single object. - Can validate that non-empty file data has been bound to the form.
- Error message keys:
required
,invalid
,missing
,empty
,max_length
Has two optional arguments for validation,
max_length
andallow_empty_file
. If provided, these ensure that the file name is at most the given length, and that validation will succeed even if the file content is empty.To learn more about the
UploadedFile
object, see the file uploads documentation.When you use a
FileField
in a form, you must also remember to bind the file data to the form.The
max_length
error refers to the length of the filename. In the error message for that key,%(max)d
will be replaced with the maximum filename length and%(length)d
will be replaced with the current filename length.- Default widget:
FilePathField
¶
-
class
FilePathField
(**kwargs)[source]¶ - Default widget:
Select
- Empty value:
''
(an empty string) - Normalizes to: A string.
- Validates that the selected choice exists in the list of choices.
- Error message keys:
required
,invalid_choice
The field allows choosing from files inside a certain directory. It takes five extra arguments; only
path
is required:-
path
¶ The absolute path to the directory whose contents you want listed. This directory must exist.
-
recursive
¶ If
False
(the default) only the direct contents ofpath
will be offered as choices. IfTrue
, the directory will be descended into recursively and all descendants will be listed as choices.
-
match
¶ A regular expression pattern; only files with names matching this expression will be allowed as choices.
-
allow_files
¶ Optional. Either
True
orFalse
. Default isTrue
. Specifies whether files in the specified location should be included. Either this orallow_folders
must beTrue
.
-
allow_folders
¶ Optional. Either
True
orFalse
. Default isFalse
. Specifies whether folders in the specified location should be included. Either this orallow_files
must beTrue
.
- Default widget:
FloatField
¶
-
class
FloatField
(**kwargs)[source]¶ - Default widget:
NumberInput
whenField.localize
isFalse
, elseTextInput
. - Empty value:
None
- Normalizes to: A Python float.
- Validates that the given value is a float. Uses
MaxValueValidator
andMinValueValidator
ifmax_value
andmin_value
are provided. Leading and trailing whitespace is allowed, as in Python’sfloat()
function. - Error message keys:
required
,invalid
,max_value
,min_value
Takes two optional arguments for validation,
max_value
andmin_value
. These control the range of values permitted in the field.- Default widget:
ImageField
¶
-
class
ImageField
(**kwargs)[source]¶ - Default widget:
ClearableFileInput
- Empty value:
None
- Normalizes to: An
UploadedFile
object that wraps the file content and file name into a single object. - Validates that file data has been bound to the form. Also uses
FileExtensionValidator
to validate that the file extension is supported by Pillow. - Error message keys:
required
,invalid
,missing
,empty
,invalid_image
Using an
ImageField
requires that Pillow is installed with support for the image formats you use. If you encounter acorrupt image
error when you upload an image, it usually means that Pillow doesn’t understand its format. To fix this, install the appropriate library and reinstall Pillow.When you use an
ImageField
on a form, you must also remember to bind the file data to the form.After the field has been cleaned and validated, the
UploadedFile
object will have an additionalimage
attribute containing the Pillow Image instance used to check if the file was a valid image. Pillow closes the underlying file descriptor after verifying an image, so while non-image data attributes, such asformat
,height
, andwidth
, are available, methods that access the underlying image data, such asgetdata()
orgetpixel()
, cannot be used without reopening the file. For example:>>> from PIL import Image >>> from django import forms >>> from django.core.files.uploadedfile import SimpleUploadedFile >>> class ImageForm(forms.Form): ... img = forms.ImageField() >>> file_data = {'img': SimpleUploadedFile('test.png', <file data>)} >>> form = ImageForm({}, file_data) # Pillow closes the underlying file descriptor. >>> form.is_valid() True >>> image_field = form.cleaned_data['img'] >>> image_field.image <PIL.PngImagePlugin.PngImageFile image mode=RGBA size=191x287 at 0x7F5985045C18> >>> image_field.image.width 191 >>> image_field.image.height 287 >>> image_field.image.format 'PNG' >>> image_field.image.getdata() # Raises AttributeError: 'NoneType' object has no attribute 'seek'. >>> image = Image.open(image_field) >>> image.getdata() <ImagingCore object at 0x7f5984f874b0>
Additionally,
UploadedFile.content_type
will be updated with the image’s content type if Pillow can determine it, otherwise it will be set toNone
.- Default widget:
IntegerField
¶
-
class
IntegerField
(**kwargs)[source]¶ - Default widget:
NumberInput
whenField.localize
isFalse
, elseTextInput
. - Empty value:
None
- Normalizes to: A Python integer.
- Validates that the given value is an integer. Uses
MaxValueValidator
andMinValueValidator
ifmax_value
andmin_value
are provided. Leading and trailing whitespace is allowed, as in Python’sint()
function. - Error message keys:
required
,invalid
,max_value
,min_value
The
max_value
andmin_value
error messages may contain%(limit_value)s
, which will be substituted by the appropriate limit.Takes two optional arguments for validation:
-
max_value
¶
-
min_value
¶ These control the range of values permitted in the field.
- Default widget:
JSONField
¶
-
class
JSONField
(encoder=None, decoder=None, **kwargs)[source]¶ - New in Django 3.1.
A field which accepts JSON encoded data for a
JSONField
.- Default widget:
Textarea
- Empty value:
None
- Normalizes to: A Python representation of the JSON value (usually as a
dict
,list
, orNone
), depending onJSONField.decoder
. - Validates that the given value is a valid JSON.
- Error message keys:
required
,invalid
Takes two optional arguments:
-
encoder
¶ A
json.JSONEncoder
subclass to serialize data types not supported by the standard JSON serializer (e.g.datetime.datetime
orUUID
). For example, you can use theDjangoJSONEncoder
class.Defaults to
json.JSONEncoder
.
-
decoder
¶ A
json.JSONDecoder
subclass to deserialize the input. Your deserialization may need to account for the fact that you can’t be certain of the input type. For example, you run the risk of returning adatetime
that was actually a string that just happened to be in the same format chosen fordatetime
s.The
decoder
can be used to validate the input. Ifjson.JSONDecodeError
is raised during the deserialization, aValidationError
will be raised.Defaults to
json.JSONDecoder
.
User friendly forms
JSONField
is not particularly user friendly in most cases. However, it is a useful way to format data from a client-side widget for submission to the server. - Default widget:
GenericIPAddressField
¶
-
class
GenericIPAddressField
(**kwargs)[source]¶ A field containing either an IPv4 or an IPv6 address.
- Default widget:
TextInput
- Empty value:
''
(an empty string) - Normalizes to: A string. IPv6 addresses are normalized as described below.
- Validates that the given value is a valid IP address.
- Error message keys:
required
,invalid
The IPv6 address normalization follows RFC 4291#section-2.2 section 2.2, including using the IPv4 format suggested in paragraph 3 of that section, like
::ffff:192.0.2.0
. For example,2001:0::0:01
would be normalized to2001::1
, and::ffff:0a0a:0a0a
to::ffff:10.10.10.10
. All characters are converted to lowercase.Takes two optional arguments:
-
protocol
¶ Limits valid inputs to the specified protocol. Accepted values are
both
(default),IPv4
orIPv6
. Matching is case insensitive.
-
unpack_ipv4
¶ Unpacks IPv4 mapped addresses like
::ffff:192.0.2.1
. If this option is enabled that address would be unpacked to192.0.2.1
. Default is disabled. Can only be used whenprotocol
is set to'both'
.
- Default widget:
MultipleChoiceField
¶
-
class
MultipleChoiceField
(**kwargs)[source]¶ - Default widget:
SelectMultiple
- Empty value:
[]
(an empty list) - Normalizes to: A list of strings.
- Validates that every value in the given list of values exists in the list of choices.
- Error message keys:
required
,invalid_choice
,invalid_list
The
invalid_choice
error message may contain%(value)s
, which will be replaced with the selected choice.Takes one extra required argument,
choices
, as forChoiceField
.- Default widget:
TypedMultipleChoiceField
¶
-
class
TypedMultipleChoiceField
(**kwargs)[source]¶ Just like a
MultipleChoiceField
, exceptTypedMultipleChoiceField
takes two extra arguments,coerce
andempty_value
.- Default widget:
SelectMultiple
- Empty value: Whatever you’ve given as
empty_value
- Normalizes to: A list of values of the type provided by the
coerce
argument. - Validates that the given values exists in the list of choices and can be coerced.
- Error message keys:
required
,invalid_choice
The
invalid_choice
error message may contain%(value)s
, which will be replaced with the selected choice.Takes two extra arguments,
coerce
andempty_value
, as forTypedChoiceField
.- Default widget:
NullBooleanField
¶
-
class
NullBooleanField
(**kwargs)[source]¶ - Default widget:
NullBooleanSelect
- Empty value:
None
- Normalizes to: A Python
True
,False
orNone
value. - Validates nothing (i.e., it never raises a
ValidationError
).
NullBooleanField
may be used with widgets such asSelect
orRadioSelect
by providing the widgetchoices
:NullBooleanField( widget=Select( choices=[ ('', 'Unknown'), (True, 'Yes'), (False, 'No'), ] ) )
- Default widget:
RegexField
¶
-
class
RegexField
(**kwargs)[source]¶ - Default widget:
TextInput
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A string.
- Uses
RegexValidator
to validate that the given value matches a certain regular expression. - Error message keys:
required
,invalid
Takes one required argument:
-
regex
¶ A regular expression specified either as a string or a compiled regular expression object.
Also takes
max_length
,min_length
,strip
, andempty_value
which work just as they do forCharField
.-
strip
¶ Defaults to
False
. If enabled, stripping will be applied before the regex validation.
- Default widget:
SlugField
¶
-
class
SlugField
(**kwargs)[source]¶ - Default widget:
TextInput
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A string.
- Uses
validate_slug
orvalidate_unicode_slug
to validate that the given value contains only letters, numbers, underscores, and hyphens. - Error messages:
required
,invalid
This field is intended for use in representing a model
SlugField
in forms.Takes two optional parameters:
-
allow_unicode
¶ A boolean instructing the field to accept Unicode letters in addition to ASCII letters. Defaults to
False
.
-
empty_value
¶ The value to use to represent “empty”. Defaults to an empty string.
- Default widget:
TimeField
¶
-
class
TimeField
(**kwargs)[source]¶ - Default widget:
TimeInput
- Empty value:
None
- Normalizes to: A Python
datetime.time
object. - Validates that the given value is either a
datetime.time
or string formatted in a particular time format. - Error message keys:
required
,invalid
Takes one optional argument:
-
input_formats
¶ A list of formats used to attempt to convert a string to a valid
datetime.time
object.
If no
input_formats
argument is provided, the default input formats are taken fromTIME_INPUT_FORMATS
ifUSE_L10N
isFalse
, or from the active locale formatTIME_INPUT_FORMATS
key if localization is enabled. See also format localization.- Default widget:
URLField
¶
-
class
URLField
(**kwargs)[source]¶ - Default widget:
URLInput
- Empty value: Whatever you’ve given as
empty_value
. - Normalizes to: A string.
- Uses
URLValidator
to validate that the given value is a valid URL. - Error message keys:
required
,invalid
Has three optional arguments
max_length
,min_length
, andempty_value
which work just as they do forCharField
.- Default widget:
Slightly complex built-in Field
classes¶
ComboField
¶
-
class
ComboField
(**kwargs)[source]¶ - Default widget:
TextInput
- Empty value:
''
(an empty string) - Normalizes to: A string.
- Validates the given value against each of the fields specified
as an argument to the
ComboField
. - Error message keys:
required
,invalid
Takes one extra required argument:
-
fields
¶ The list of fields that should be used to validate the field’s value (in the order in which they are provided).
>>> from django.forms import ComboField >>> f = ComboField(fields=[CharField(max_length=20), EmailField()]) >>> f.clean('test@example.com') 'test@example.com' >>> f.clean('longemailaddress@example.com') Traceback (most recent call last): ... ValidationError: ['Ensure this value has at most 20 characters (it has 28).']
- Default widget:
MultiValueField
¶
-
class
MultiValueField
(fields=(), **kwargs)[source]¶ - Default widget:
TextInput
- Empty value:
''
(an empty string) - Normalizes to: the type returned by the
compress
method of the subclass. - Validates the given value against each of the fields specified
as an argument to the
MultiValueField
. - Error message keys:
required
,invalid
,incomplete
Aggregates the logic of multiple fields that together produce a single value.
This field is abstract and must be subclassed. In contrast with the single-value fields, subclasses of
MultiValueField
must not implementclean()
but instead - implementcompress()
.Takes one extra required argument:
-
fields
¶ A tuple of fields whose values are cleaned and subsequently combined into a single value. Each value of the field is cleaned by the corresponding field in
fields
– the first value is cleaned by the first field, the second value is cleaned by the second field, etc. Once all fields are cleaned, the list of clean values is combined into a single value bycompress()
.
Also takes some optional arguments:
-
require_all_fields
¶ Defaults to
True
, in which case arequired
validation error will be raised if no value is supplied for any field.When set to
False
, theField.required
attribute can be set toFalse
for individual fields to make them optional. If no value is supplied for a required field, anincomplete
validation error will be raised.A default
incomplete
error message can be defined on theMultiValueField
subclass, or different messages can be defined on each individual field. For example:from django.core.validators import RegexValidator class PhoneField(MultiValueField): def __init__(self, **kwargs): # Define one message for all fields. error_messages = { 'incomplete': 'Enter a country calling code and a phone number.', } # Or define a different message for each field. fields = ( CharField( error_messages={'incomplete': 'Enter a country calling code.'}, validators=[ RegexValidator(r'^[0-9]+$', 'Enter a valid country calling code.'), ], ), CharField( error_messages={'incomplete': 'Enter a phone number.'}, validators=[RegexValidator(r'^[0-9]+$', 'Enter a valid phone number.')], ), CharField( validators=[RegexValidator(r'^[0-9]+$', 'Enter a valid extension.')], required=False, ), ) super().__init__( error_messages=error_messages, fields=fields, require_all_fields=False, **kwargs )
-
widget
¶ Must be a subclass of
django.forms.MultiWidget
. Default value isTextInput
, which probably is not very useful in this case.
-
compress
(data_list)[source]¶ Takes a list of valid values and returns a “compressed” version of those values – in a single value. For example,
SplitDateTimeField
is a subclass which combines a time field and a date field into adatetime
object.This method must be implemented in the subclasses.
- Default widget:
SplitDateTimeField
¶
-
class
SplitDateTimeField
(**kwargs)[source]¶ - Default widget:
SplitDateTimeWidget
- Empty value:
None
- Normalizes to: A Python
datetime.datetime
object. - Validates that the given value is a
datetime.datetime
or string formatted in a particular datetime format. - Error message keys:
required
,invalid
,invalid_date
,invalid_time
Takes two optional arguments:
-
input_date_formats
¶ A list of formats used to attempt to convert a string to a valid
datetime.date
object.
If no
input_date_formats
argument is provided, the default input formats forDateField
are used.-
input_time_formats
¶ A list of formats used to attempt to convert a string to a valid
datetime.time
object.
If no
input_time_formats
argument is provided, the default input formats forTimeField
are used.- Default widget:
Fields which handle relationships¶
Two fields are available for representing relationships between
models: ModelChoiceField
and
ModelMultipleChoiceField
. Both of these fields require a
single queryset
parameter that is used to create the choices for
the field. Upon form validation, these fields will place either one
model object (in the case of ModelChoiceField
) or multiple model
objects (in the case of ModelMultipleChoiceField
) into the
cleaned_data
dictionary of the form.
For more complex uses, you can specify queryset=None
when declaring the
form field and then populate the queryset
in the form’s __init__()
method:
class FooMultipleChoiceForm(forms.Form):
foo_select = forms.ModelMultipleChoiceField(queryset=None)
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.fields['foo_select'].queryset = ...
Both ModelChoiceField
and ModelMultipleChoiceField
have an iterator
attribute which specifies the class used to iterate over the queryset when
generating choices. See Iterating relationship choices for details.
ModelChoiceField
¶
-
class
ModelChoiceField
(**kwargs)[source]¶ - Default widget:
Select
- Empty value:
None
- Normalizes to: A model instance.
- Validates that the given id exists in the queryset.
- Error message keys:
required
,invalid_choice
Allows the selection of a single model object, suitable for representing a foreign key. Note that the default widget for
ModelChoiceField
becomes impractical when the number of entries increases. You should avoid using it for more than 100 items.A single argument is required:
-
queryset
¶ A
QuerySet
of model objects from which the choices for the field are derived and which is used to validate the user’s selection. It’s evaluated when the form is rendered.
ModelChoiceField
also takes two optional arguments:-
empty_label
¶ By default the
<select>
widget used byModelChoiceField
will have an empty choice at the top of the list. You can change the text of this label (which is"---------"
by default) with theempty_label
attribute, or you can disable the empty label entirely by settingempty_label
toNone
:# A custom empty label field1 = forms.ModelChoiceField(queryset=..., empty_label="(Nothing)") # No empty label field2 = forms.ModelChoiceField(queryset=..., empty_label=None)
Note that if a
ModelChoiceField
is required and has a default initial value, no empty choice is created (regardless of the value ofempty_label
).
-
to_field_name
¶ This optional argument is used to specify the field to use as the value of the choices in the field’s widget. Be sure it’s a unique field for the model, otherwise the selected value could match more than one object. By default it is set to
None
, in which case the primary key of each object will be used. For example:# No custom to_field_name field1 = forms.ModelChoiceField(queryset=...)
would yield:
<select id="id_field1" name="field1"> <option value="obj1.pk">Object1</option> <option value="obj2.pk">Object2</option> ... </select>
and:
# to_field_name provided field2 = forms.ModelChoiceField(queryset=..., to_field_name="name")
would yield:
<select id="id_field2" name="field2"> <option value="obj1.name">Object1</option> <option value="obj2.name">Object2</option> ... </select>
ModelChoiceField
also has the attribute:-
iterator
¶ The iterator class used to generate field choices from
queryset
. By default,ModelChoiceIterator
.
The
__str__()
method of the model will be called to generate string representations of the objects for use in the field’s choices. To provide customized representations, subclassModelChoiceField
and overridelabel_from_instance
. This method will receive a model object and should return a string suitable for representing it. For example:from django.forms import ModelChoiceField class MyModelChoiceField(ModelChoiceField): def label_from_instance(self, obj): return "My Object #%i" % obj.id
- Default widget:
ModelMultipleChoiceField
¶
-
class
ModelMultipleChoiceField
(**kwargs)[source]¶ - Default widget:
SelectMultiple
- Empty value: An empty
QuerySet
(self.queryset.none()
) - Normalizes to: A
QuerySet
of model instances. - Validates that every id in the given list of values exists in the queryset.
- Error message keys:
required
,invalid_list
,invalid_choice
,invalid_pk_value
The
invalid_choice
message may contain%(value)s
and theinvalid_pk_value
message may contain%(pk)s
, which will be substituted by the appropriate values.Allows the selection of one or more model objects, suitable for representing a many-to-many relation. As with
ModelChoiceField
, you can uselabel_from_instance
to customize the object representations.A single argument is required:
-
queryset
¶ Same as
ModelChoiceField.queryset
.
Takes one optional argument:
-
to_field_name
¶ Same as
ModelChoiceField.to_field_name
.
ModelMultipleChoiceField
also has the attribute:-
iterator
¶ Same as
ModelChoiceField.iterator
.
- Default widget:
Deprecated since version 3.1: The list
message is deprecated, use invalid_list
instead.
Iterating relationship choices¶
By default, ModelChoiceField
and ModelMultipleChoiceField
use
ModelChoiceIterator
to generate their field choices
.
When iterated, ModelChoiceIterator
yields 2-tuple choices containing
ModelChoiceIteratorValue
instances as the first value
element in
each choice. ModelChoiceIteratorValue
wraps the choice value while
maintaining a reference to the source model instance that can be used in custom
widget implementations, for example, to add data-* attributes to
<option>
elements.
For example, consider the following models:
from django.db import models
class Topping(models.Model):
name = models.CharField(max_length=100)
price = models.DecimalField(decimal_places=2, max_digits=6)
def __str__(self):
return self.name
class Pizza(models.Model):
topping = models.ForeignKey(Topping, on_delete=models.CASCADE)
You can use a Select
widget subclass to include
the value of Topping.price
as the HTML attribute data-price
for each
<option>
element:
from django import forms
class ToppingSelect(forms.Select):
def create_option(self, name, value, label, selected, index, subindex=None, attrs=None):
option = super().create_option(name, value, label, selected, index, subindex, attrs)
if value:
option['attrs']['data-price'] = value.instance.price
return option
class PizzaForm(forms.ModelForm):
class Meta:
model = Pizza
fields = ['topping']
widgets = {'topping': ToppingSelect}
This will render the Pizza.topping
select as:
<select id="id_topping" name="topping" required>
<option value="" selected>---------</option>
<option value="1" data-price="1.50">mushrooms</option>
<option value="2" data-price="1.25">onions</option>
<option value="3" data-price="1.75">peppers</option>
<option value="4" data-price="2.00">pineapple</option>
</select>
For more advanced usage you may subclass ModelChoiceIterator
in order to
customize the yielded 2-tuple choices.
ModelChoiceIterator
¶
-
class
ModelChoiceIterator
(field)¶ The default class assigned to the
iterator
attribute ofModelChoiceField
andModelMultipleChoiceField
. An iterable that yields 2-tuple choices from the queryset.A single argument is required:
-
field
¶ The instance of
ModelChoiceField
orModelMultipleChoiceField
to iterate and yield choices.
ModelChoiceIterator
has the following method:-
__iter__
()¶ Yields 2-tuple choices, in the
(value, label)
format used byChoiceField.choices
. The firstvalue
element is aModelChoiceIteratorValue
instance.Changed in Django 3.1:In older versions, the first
value
element in the choice tuple is thefield
value itself, rather than aModelChoiceIteratorValue
instance. In most cases this proxies transparently but, if you need thefield
value itself, use theModelChoiceIteratorValue.value
attribute instead.
-
ModelChoiceIteratorValue
¶
-
class
ModelChoiceIteratorValue
(value, instance)¶ - New in Django 3.1.
Two arguments are required:
-
value
¶ The value of the choice. This value is used to render the
value
attribute of an HTML<option>
element.
-
instance
¶ The model instance from the queryset. The instance can be accessed in custom
ChoiceWidget.create_option()
implementations to adjust the rendered HTML.
ModelChoiceIteratorValue
has the following method:-
__str__
()¶ Return
value
as a string to be rendered in HTML.
-
Creating custom fields¶
If the built-in Field
classes don’t meet your needs, you can create custom
Field
classes. To do this, create a subclass of django.forms.Field
. Its
only requirements are that it implement a clean()
method and that its
__init__()
method accept the core arguments mentioned above (required
,
label
, initial
, widget
, help_text
).
You can also customize how a field will be accessed by overriding
get_bound_field()
.