# Τεκμηρίωση του Django - 6.0.7

# Form fields

class Field

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("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(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, 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 a string for `label` if that default behavior doesn’t result in an adequate label. Use an empty string (`""`) to hide the 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)
    <div>Your name:<input type="text" name="name" required></div>
    <div>Your website:<input type="url" name="url"></div>
    <div>Comment:<input type="text" name="comment" required></div>

### `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)
    <div><label for="id_age">Age?</label><input type="number" name="age" required id="id_age"></div>
    <div><label for="id_nationality">Nationality?</label><input type="text" name="nationality" required id="id_nationality"></div>
    <div><label for="id_captcha_answer">2 + 2 =</label><input type="number" name="captcha_answer" required id="id_captcha_answer"></div>

### `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="https://")
    ...     comment = forms.CharField()
    ...
    >>> f = CommentForm(auto_id=False)
    >>> print(f)
    <div>Name:<input type="text" name="name" value="Your name" required></div>
    <div>Url:<input type="url" name="url" value="https://" required></div>
    <div>Comment:<input type="text" name="comment" required></div>

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": "https://"}
    >>> f = CommentForm(default_data, auto_id=False)
    >>> print(f)
    <div>Name:
      <input type="text" name="name" value="Your name" required>
    </div>
    <div>Url:
      <ul class="errorlist"><li>Enter a valid URL.</li></ul>
      <input type="url" name="url" value="https://" required aria-invalid="true">
    </div>
    <div>Comment:
      <ul class="errorlist"><li>This field is required.</li></ul>
      <input type="text" name="comment" required aria-invalid="true">
    </div>

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="https://")
    ...     comment = forms.CharField()
    ...
    >>> data = {"name": "", "url": "", "comment": "Foo"}
    >>> f = CommentForm(data)
    >>> f.is_valid()
    False
    # The form does *not* fallback 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())
    <div><label for="id_day">Day:</label><input type="text" name="day" value="2023-02-11" required id="id_day"></div>

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()
    ...     contact_email = forms.EmailField(help_text="Your email (so we can reply).")
    ...
    >>> f = HelpTextContactForm(auto_id=False)
    >>> print(f)
    <div>Subject:<div class="helptext">100 characters max.</div><input type="text" name="subject" maxlength="100" required></div>
    <div>Message:<input type="text" name="message" required></div>
    <div>Contact email:<div class="helptext">Your email (so we can reply).</div><input type="email" name="contact_email" maxlength="320" required></div>

When a field has help text it is associated with its input using the `aria-describedby` HTML attribute. If the widget is rendered in a `<fieldset>` then `aria-describedby` is added to this element, otherwise it is added to the widget’s `<input>`:

    >>> from django import forms
    >>> class UserForm(forms.Form):
    ...     username = forms.CharField(max_length=255, help_text="e.g., user@example.com")
    ...
    >>> f = UserForm()
    >>> print(f)
    <div>
    <label for="id_username">Username:</label>
    <div class="helptext" id="id_username_helptext">e.g., user@example.com</div>
    <input type="text" name="username" maxlength="255" required aria-describedby="id_username_helptext" id="id_username">
    </div>

When adding a custom `aria-describedby` attribute, make sure to also include the `id` of the `help_text` element (if used) in the desired order. For screen reader users, descriptions will be read in their order of appearance inside `aria-describedby`:

    >>> class UserForm(forms.Form):
    ...     username = forms.CharField(
    ...         max_length=255,
    ...         help_text="e.g., user@example.com",
    ...         widget=forms.TextInput(
    ...             attrs={"aria-describedby": "custom-description id_username_helptext"},
    ...         ),
    ...     )
    ...
    >>> f = UserForm()
    >>> print(f["username"])
    <input type="text" name="username" aria-describedby="custom-description id_username_helptext" maxlength="255" id="id_username" required>

### `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.

### `template_name`

Field.template_name

The `template_name` argument allows a custom template to be used when the field is rendered with `as_field_group()`. By default this value is set to `"django/forms/field.html"`. Can be changed per field by overriding this attribute or more generally by overriding the default template, see also Overriding built-in field templates.

### `bound_field_class`

Field.bound_field_class

The `bound_field_class` attribute allows a per-field override of `Form.bound_field_class`.

## Checking if the field data has changed

### `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.

## 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)

  - Default widget: `CheckboxInput`

  - Empty value: `False`

  - Normalizes to: A Python `True` or `False` value.

  - Validates that the value is `True` (e.g. the check box is checked) if the field has `required=True`.

  - Error message keys: `required`

  Σημείωση

  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`.

### `CharField`

class CharField(**kwargs)

  - Default widget: `TextInput`

  - Empty value: Whatever you’ve given as `empty_value`.

  - Normalizes to: A string.

  - Uses `MaxLengthValidator` and `MinLengthValidator` if `max_length` and `min_length` are provided. Otherwise, all inputs are valid.

  - Error message keys: `required`, `max_length`, `min_length`

  Has the following 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.

### `ChoiceField`

class ChoiceField(**kwargs)

  - 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 type, 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.

  Choice type

  This field normalizes choices to strings, so if choices are required in other data types, such as integers or booleans, consider using `TypedChoiceField` instead.

### `DateField`

class DateField(**kwargs)

  - 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

    An iterable 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 the active locale format `DATE_INPUT_FORMATS` key, or from `DATE_INPUT_FORMATS` if localization is disabled. See also format localization.

### `DateTimeField`

class DateTimeField(**kwargs)

  - 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

    An iterable 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 the active locale format `DATETIME_INPUT_FORMATS` and `DATE_INPUT_FORMATS` keys, or from `DATETIME_INPUT_FORMATS` and `DATE_INPUT_FORMATS` if localization is disabled. See also format localization.

### `DecimalField`

class DecimalField(**kwargs)

  - Default widget: `NumberInput` when `Field.localize` is `False`, else `TextInput`.

  - Empty value: `None`

  - Normalizes to: A Python `decimal`.

  - Validates that the given value is a decimal. Uses `MaxValueValidator` and `MinValueValidator` if `max_value` and `min_value` are provided. Uses `StepValueValidator` if `step_size` is provided. Leading and trailing whitespace is ignored.

  - Error message keys: `required`, `invalid`, `max_value`, `min_value`, `max_digits`, `max_decimal_places`, `max_whole_digits`, `step_size`.

  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 five 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.

  step_size

    Limit valid inputs to an integral multiple of `step_size`. If `min_value` is also provided, it’s added as an offset to determine if the step size matches.

### `DurationField`

class DurationField(**kwargs)

  - 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 between `datetime.timedelta.min` and `datetime.timedelta.max`.

  - Error message keys: `required`, `invalid`, `overflow`.

  Accepts any format understood by `parse_duration()`.

### `EmailField`

class EmailField(**kwargs)

  - 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 the optional arguments `max_length`, `min_length`, and `empty_value` which work just as they do for `CharField`. The `max_length` argument defaults to 320 (see RFC 3696 Section 3).

### `FileField`

class FileField(**kwargs)

  - 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 the 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.

### `FilePathField`

class FilePathField(**kwargs)

  - 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 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`.

  `FilePathField` has the following method:

  set_choices()
    New in Django 6.1.

    Scans the directory at `path` and refreshes the field’s choices. This is called automatically during `__init__()`, but it can also be called explicitly to pick up files added to the directory after the field was first instantiated (usually at server startup). For example, call it in a form’s `__init__()` to get fresh choices per request:

        class MyForm(forms.Form):
            my_file = forms.FilePathField(path="/path/to/dir")

            def __init__(self, *args, **kwargs):
                super().__init__(*args, **kwargs)
                self.fields["my_file"].set_choices()

### `FloatField`

class FloatField(**kwargs)

  - Default widget: `NumberInput` when `Field.localize` is `False`, else `TextInput`.

  - Empty value: `None`

  - Normalizes to: A Python float.

  - Validates that the given value is a float. Uses `MaxValueValidator` and `MinValueValidator` if `max_value` and `min_value` are provided. Uses `StepValueValidator` if `step_size` is provided. Leading and trailing whitespace is allowed, as in Python’s `float()` function.

  - Error message keys: `required`, `invalid`, `max_value`, `min_value`, `step_size`.

  Takes three optional arguments:

  max_value
  min_value

    These control the range of values permitted in the field.

  step_size

    Limit valid inputs to an integral multiple of `step_size`. If `min_value` is also provided, it’s added as an offset to determine if the step size matches.

### `GenericIPAddressField`

class GenericIPAddressField(**kwargs)

  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`, `max_length`

  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 three 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'`.

  max_length

    Defaults to 39, and behaves the same way as it does for `CharField`.

### `ImageField`

class ImageField(**kwargs)

  - 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 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", b"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`.

### `IntegerField`

class IntegerField(**kwargs)

  - Default widget: `NumberInput` when `Field.localize` is `False`, else `TextInput`.

  - Empty value: `None`

  - Normalizes to: A Python integer.

  - Validates that the given value is an integer. Uses `MaxValueValidator` and `MinValueValidator` if `max_value` and `min_value` are provided. Uses `StepValueValidator` if `step_size` is provided. Leading and trailing whitespace is allowed, as in Python’s `int()` function.

  - Error message keys: `required`, `invalid`, `max_value`, `min_value`, `step_size`

  The `max_value`, `min_value` and `step_size` error messages may contain `%(limit_value)s`, which will be substituted by the appropriate limit.

  Takes three optional arguments for validation:

  max_value
  min_value

    These control the range of values permitted in the field.

  step_size

    Limit valid inputs to an integral multiple of `step_size`. If `min_value` is also provided, it’s added as an offset to determine if the step size matches.

### `JSONField`

class JSONField(encoder=None, decoder=None, **kwargs)

  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`, or `None`), depending on `JSONField.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` 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 `datetime`s.

    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`.

  Σημείωση

  If you use a `ModelForm`, the `encoder` and `decoder` from `JSONField` will be used.

  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.

### `MultipleChoiceField`

class MultipleChoiceField(**kwargs)

  - 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 for `ChoiceField`.

### `NullBooleanField`

class NullBooleanField(**kwargs)

  - Default widget: `NullBooleanSelect`

  - Empty value: `None`

  - Normalizes to: A Python `True`, `False` or `None` value.

  - Validates nothing (i.e., it never raises a `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"),
              ]
          )
      )

### `RegexField`

class RegexField(**kwargs)

  - 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`, 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.

### `SlugField`

class SlugField(**kwargs)

  - Default widget: `TextInput`

  - Empty value: Whatever you’ve given as `empty_value`.

  - Normalizes to: A string.

  - Uses `validate_slug` or `validate_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.

### `TimeField`

class TimeField(**kwargs)

  - 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

    An iterable 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 the active locale format `TIME_INPUT_FORMATS` key, or from `TIME_INPUT_FORMATS` if localization is disabled. See also format localization.

### `TypedChoiceField`

class TypedChoiceField(**kwargs)

  Just like a `ChoiceField`, except `TypedChoiceField` takes two extra arguments, `coerce` and `empty_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 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.

### `TypedMultipleChoiceField`

class TypedMultipleChoiceField(**kwargs)

  Just like a `MultipleChoiceField`, except `TypedMultipleChoiceField` takes two extra arguments, `coerce` and `empty_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` and `empty_value`, as for `TypedChoiceField`.

### `URLField`

class URLField(**kwargs)

  - 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 the optional arguments `max_length`, `min_length`, `empty_value` which work just as they do for `CharField`, and one more argument:

  assume_scheme

    The scheme assumed for URLs provided without one. Defaults to `"https"`. For example, if `assume_scheme` is `"https"` and the provided value is `"example.com"`, the normalized value will be `"https://example.com"`.

### `UUIDField`

class UUIDField(**kwargs)

  - Default widget: `TextInput`

  - Empty value: `None`

  - Normalizes to: A `UUID` object.

  - Error message keys: `required`, `invalid`

  This field will accept any string format accepted as the `hex` argument to the `UUID` constructor.

## Slightly complex built-in `Field` classes

### `ComboField`

class ComboField(**kwargs)

  - 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).']

### `MultiValueField`

class MultiValueField(fields=(), **kwargs)

  - 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 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.

### `SplitDateTimeField`

class SplitDateTimeField(**kwargs)

  - 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 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.

## 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)

  - 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`

  The `invalid_choice` error message may contain `%(value)s`, which will be replaced with the selected 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 several 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 `"- Select an option -"` 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 no empty choice is created (regardless of the value of `empty_label`) if a `ModelChoiceField` is required and has a default initial value, or a `widget` is set to `RadioSelect` and the `blank` argument is `False`.

  Changed in Django 6.1:

  The default empty label was changed from `"---------"` to `"- Select an option -"`.

  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>

  blank

    When using the `RadioSelect` widget, this optional boolean argument determines whether an empty choice is created. By default, `blank` is `False`, in which case no empty choice is created.

  `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

### `ModelMultipleChoiceField`

class ModelMultipleChoiceField(**kwargs)

  - 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 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`.

### 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 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.

#### `ModelChoiceIteratorValue`

class 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.

## 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 `bound_field_class` or override `Field.get_bound_field()` if you need more flexibility when creating the `BoundField`:

Field.get_bound_field(form, field_name)

  Takes an instance of `Form` and the name of the field. The returned `BoundField` instance will be used when accessing the field in a template.

See Customizing BoundField for examples of overriding a `BoundField`.