class Field(**kwargs) 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.
Field.clean(value) 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('[email protected]')
'[email protected]'
>>> f.clean('invalid email address')
Traceback (most recent call last):
...
ValidationError: ['Enter a valid email address.']
Each Field class constructor takes at least these arguments. Some Field classes take additional, field-specific arguments, but the following should always be accepted:
requiredField.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.
labelField.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_suffixField.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>
initialField.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.
widgetField.widget The widget argument lets you specify a Widget class to use when rendering this Field. See Widgets for more information.
help_textField.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_messagesField.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.
validatorsField.validators The validators argument lets you provide a list of validation functions for this field.
See the validators documentation for more information.
localizeField.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.
disabledField.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.
has_changed()Field.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.
Field classesNaturally, 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).
BooleanFieldclass BooleanField(**kwargs) CheckboxInput
False
True or False value.True (e.g. the check box is checked) if the field has required=True.required
Note
Since all Field subclasses have required=True by default, the validation condition here is important. If you want to include a boolean in your form that can be either True or False (e.g. a checked or unchecked checkbox), you must remember to pass in required=False when creating the BooleanField.
CharFieldclass CharField(**kwargs) TextInput
empty_value.MaxLengthValidator and MinLengthValidator if max_length and min_length are provided. Otherwise, all inputs are valid.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.
ChoiceFieldclass ChoiceField(**kwargs) Select
'' (an empty string)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.
TypedChoiceFieldclass TypedChoiceField(**kwargs) Just like a ChoiceField, except TypedChoiceField takes two extra arguments, coerce and empty_value.
Select
empty_value.coerce argument.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 in choices.
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 the coerce argument, so choose it accordingly.
DateFieldclass DateField(**kwargs) DateInput
None
datetime.date object.datetime.date, datetime.datetime or string formatted in a particular date format.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 from DATE_INPUT_FORMATS if USE_L10N is False, or from the active locale format DATE_INPUT_FORMATS key if localization is enabled. See also format localization.
DateTimeFieldclass DateTimeField(**kwargs) DateTimeInput
None
datetime.datetime object.datetime.datetime, datetime.date or string formatted in a particular datetime format.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 from DATETIME_INPUT_FORMATS and DATE_INPUT_FORMATS if USE_L10N is False, or from the active locale format DATETIME_INPUT_FORMATS and DATE_INPUT_FORMATS keys if localization is enabled. See also format localization.
Support for ISO 8601 date string parsing (including optional timezone) was added.
The fallback on DATE_INPUT_FORMATS in the default input_formats was added.
DecimalFieldclass DecimalField(**kwargs) NumberInput when Field.localize is False, else TextInput.None
decimal.MaxValueValidator and MinValueValidator if max_value and min_value are provided. Leading and trailing whitespace is ignored.required, invalid, max_value, min_value, max_digits, max_decimal_places, max_whole_digits
The max_value and min_value error messages may contain %(limit_value)s, which will be substituted by the appropriate limit. Similarly, the max_digits, max_decimal_places and max_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.
DurationFieldclass DurationField(**kwargs) TextInput
None
timedelta.timedelta. The value must be between datetime.timedelta.min and datetime.timedelta.max.required, invalid, overflow.Accepts any format understood by parse_duration().
EmailFieldclass EmailField(**kwargs) EmailInput
empty_value.EmailValidator to validate that the given value is a valid email address, using a moderately complex regular expression.required, invalid
Has three optional arguments max_length, min_length, and empty_value which work just as they do for CharField.
FileFieldclass FileField(**kwargs) ClearableFileInput
None
UploadedFile object that wraps the file content and file name into a single object.required, invalid, missing, empty, max_length
Has two optional arguments for validation, max_length and allow_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.
FilePathFieldclass FilePathField(**kwargs) Select
'' (an empty string)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 of path will be offered as choices. If True, 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 or False. Default is True. Specifies whether files in the specified location should be included. Either this or allow_folders must be True.
allow_folders Optional. Either True or False. Default is False. Specifies whether folders in the specified location should be included. Either this or allow_files must be True.
FloatFieldclass FloatField(**kwargs) NumberInput when Field.localize is False, else TextInput.None
MaxValueValidator and MinValueValidator if max_value and min_value are provided. Leading and trailing whitespace is allowed, as in Python’s float() function.required, invalid, max_value, min_value
Takes two optional arguments for validation, max_value and min_value. These control the range of values permitted in the field.
ImageFieldclass ImageField(**kwargs) ClearableFileInput
None
UploadedFile object that wraps the file content and file name into a single object.FileExtensionValidator to validate that the file extension is supported by Pillow.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 a corrupt 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 additional image 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 as format, height, and width, are available, methods that access the underlying image data, such as getdata() or getpixel(), 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 to None.
IntegerFieldclass IntegerField(**kwargs) NumberInput when Field.localize is False, else TextInput.None
MaxValueValidator and MinValueValidator if max_value and min_value are provided. Leading and trailing whitespace is allowed, as in Python’s int() function.required, invalid, max_value, min_value
The max_value and min_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.
JSONFieldclass JSONField(encoder=None, decoder=None, **kwargs) A field which accepts JSON encoded data for a JSONField.
Textarea
None
dict, list, or None), depending on JSONField.decoder.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 or UUID). For example, you can use the DjangoJSONEncoder 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 a datetime that was actually a string that just happened to be in the same format chosen for datetimes.
The decoder can be used to validate the input. If json.JSONDecodeError is raised during the deserialization, a ValidationError 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.
GenericIPAddressFieldclass GenericIPAddressField(**kwargs) A field containing either an IPv4 or an IPv6 address.
TextInput
'' (an empty string)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 to 2001::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 or IPv6. 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 to 192.0.2.1. Default is disabled. Can only be used when protocol is set to 'both'.
MultipleChoiceFieldclass MultipleChoiceField(**kwargs) SelectMultiple
[] (an empty list)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 for ChoiceField.
TypedMultipleChoiceFieldclass TypedMultipleChoiceField(**kwargs) Just like a MultipleChoiceField, except TypedMultipleChoiceField takes two extra arguments, coerce and empty_value.
SelectMultiple
empty_value
coerce argument.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 and empty_value, as for TypedChoiceField.
NullBooleanFieldclass NullBooleanField(**kwargs) NullBooleanSelect
None
True, False or None value.ValidationError).NullBooleanField may be used with widgets such as Select or RadioSelect by providing the widget choices:
NullBooleanField(
widget=Select(
choices=[
('', 'Unknown'),
(True, 'Yes'),
(False, 'No'),
]
)
)
RegexFieldclass RegexField(**kwargs) TextInput
empty_value.RegexValidator to validate that the given value matches a certain regular expression.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, and empty_value which work just as they do for CharField.
strip Defaults to False. If enabled, stripping will be applied before the regex validation.
SlugFieldclass SlugField(**kwargs) TextInput
empty_value.validate_slug or validate_unicode_slug to validate that the given value contains only letters, numbers, underscores, and hyphens.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.
TimeFieldclass TimeField(**kwargs) TimeInput
None
datetime.time object.datetime.time or string formatted in a particular time format.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 from TIME_INPUT_FORMATS if USE_L10N is False, or from the active locale format TIME_INPUT_FORMATS key if localization is enabled. See also format localization.
URLFieldclass URLField(**kwargs) URLInput
empty_value.URLValidator to validate that the given value is a valid URL.required, invalid
Has three optional arguments max_length, min_length, and empty_value which work just as they do for CharField.
UUIDFieldclass UUIDField(**kwargs) TextInput
None
UUID object.required, invalid
This field will accept any string format accepted as the hex argument to the UUID constructor.
Field classesComboFieldclass ComboField(**kwargs) TextInput
'' (an empty string)ComboField.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('[email protected]')
'[email protected]'
>>> f.clean('[email protected]')
Traceback (most recent call last):
...
ValidationError: ['Ensure this value has at most 20 characters (it has 28).']
MultiValueFieldclass MultiValueField(fields=(), **kwargs) TextInput
'' (an empty string)compress method of the subclass.MultiValueField.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 implement clean() but instead - implement compress().
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 by compress().
Also takes some optional arguments:
require_all_fields Defaults to True, in which case a required validation error will be raised if no value is supplied for any field.
When set to False, the Field.required attribute can be set to False for individual fields to make them optional. If no value is supplied for a required field, an incomplete validation error will be raised.
A default incomplete error message can be defined on the MultiValueField 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 is TextInput, which probably is not very useful in this case.
compress(data_list) 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 a datetime object.
This method must be implemented in the subclasses.
SplitDateTimeFieldclass SplitDateTimeField(**kwargs) SplitDateTimeWidget
None
datetime.datetime object.datetime.datetime or string formatted in a particular datetime format.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 for DateField 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 for TimeField are used.
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.
ModelChoiceFieldclass ModelChoiceField(**kwargs) Select
None
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 by ModelChoiceField will have an empty choice at the top of the list. You can change the text of this label (which is "---------" by default) with the empty_label attribute, or you can disable the empty label entirely by setting empty_label to None:
# 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 of empty_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, subclass ModelChoiceField and override label_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
ModelMultipleChoiceFieldclass ModelMultipleChoiceField(**kwargs) SelectMultiple
QuerySet (self.queryset.none())QuerySet of model instances.required, invalid_list, invalid_choice, invalid_pk_value
The invalid_choice message may contain %(value)s and the invalid_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 use label_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.
Deprecated since version 3.1: The list message is deprecated, use invalid_list instead.
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.
ModelChoiceIteratorclass ModelChoiceIterator(field) The default class assigned to the iterator attribute of ModelChoiceField and ModelMultipleChoiceField. An iterable that yields 2-tuple choices from the queryset.
A single argument is required:
field The instance of ModelChoiceField or ModelMultipleChoiceField to iterate and yield choices.
ModelChoiceIterator has the following method:
__iter__() Yields 2-tuple choices, in the (value, label) format used by ChoiceField.choices. The first value element is a ModelChoiceIteratorValue instance.
In older versions, the first value element in the choice tuple is the field value itself, rather than a ModelChoiceIteratorValue instance. In most cases this proxies transparently but, if you need the field value itself, use the ModelChoiceIteratorValue.value attribute instead.
ModelChoiceIteratorValueclass ModelChoiceIteratorValue(value, instance) 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.
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().
© Django Software Foundation and individual contributors
Licensed under the BSD License.
https://docs.djangoproject.com/en/3.2/ref/forms/fields/