Django documentation

This document is for Django's SVN release, which can be significantly different from previous releases. Get old docs here: Django 1.0

Form fields

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.forms.ValidationError exception or returns the clean value:

>>> from django import forms
>>> f = forms.EmailField()
>>> f.clean('foo@example.com')
u'foo@example.com'
>>> f.clean(u'foo@example.com')
u'foo@example.com'
>>> f.clean('invalid e-mail address')
...
ValidationError: [u'Enter a valid e-mail 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:

>>> f = forms.CharField()
>>> f.clean('foo')
u'foo'
>>> f.clean('')
...
ValidationError: [u'This field is required.']
>>> f.clean(None)
...
ValidationError: [u'This field is required.']
>>> f.clean(' ')
u' '
>>> f.clean(0)
u'0'
>>> f.clean(True)
u'True'
>>> f.clean(False)
u'False'

To specify that a field is not required, pass required=False to the Field constructor:

>>> f = forms.CharField(required=False)
>>> f.clean('foo')
u'foo'
>>> f.clean('')
u''
>>> f.clean(None)
u''
>>> f.clean(0)
u'0'
>>> f.clean(True)
u'True'
>>> f.clean(False)
u'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 be a Unicode empty string. For other Field classes, it might be None. (This varies from field to field.)

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:

>>> class CommentForm(forms.Form):
...     name = forms.CharField(label='Your name')
...     url = forms.URLField(label='Your Web site', required=False)
...     comment = forms.CharField()
>>> f = CommentForm(auto_id=False)
>>> print f
<tr><th>Your name:</th><td><input type="text" name="name" /></td></tr>
<tr><th>Your Web site:</th><td><input type="text" name="url" /></td></tr>
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>

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:

>>> 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" /></td></tr>
<tr><th>Url:</th><td><input type="text" name="url" value="http://" /></td></tr>
<tr><th>Comment:</th><td><input type="text" name="comment" /></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" /></td></tr>
<tr><th>Url:</th><td><ul class="errorlist"><li>Enter a valid URL.</li></ul><input type="text" name="url" value="http://" /></td></tr>
<tr><th>Comment:</th><td><ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="comment" /></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': [u'This field is required.'], 'name': [u'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" /><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()).

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:

>>> 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 e-mail 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" /><br />100 characters max.</td></tr>
<tr><th>Message:</th><td><input type="text" name="message" /></td></tr>
<tr><th>Sender:</th><td><input type="text" name="sender" /><br />A valid e-mail 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" /> 100 characters max.</li>
<li>Message: <input type="text" name="message" /></li>
<li>Sender: <input type="text" name="sender" /> A valid e-mail 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" /> 100 characters max.</p>
<p>Message: <input type="text" name="message" /></p>
<p>Sender: <input type="text" name="sender" /> A valid e-mail address, please.</p>
<p>Cc myself: <input type="checkbox" name="cc_myself" /></p>

error_messages

New in Django 1.0: Please, see the release notes
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:

>>> generic = forms.CharField()
>>> generic.clean('')
Traceback (most recent call last):
...
ValidationError: [u'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: [u'Please enter your name']

In the built-in Field classes section below, each Field defines the error message keys it uses.

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
Changed in Django 1.0: The empty value for a CheckboxInput (and hence the standard BooleanField) has changed to return False instead of None in the Django 1.0.

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.

CharField

class CharField(**kwargs)
  • Default widget: TextInput
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates max_length or min_length, if they are provided. Otherwise, all inputs are valid.
  • Error message keys: required, max_length, min_length

Has two optional arguments for validation:

CharField.max_length
CharField.min_length
If provided, these arguments ensure that the string is at most or at least the given length.

ChoiceField

class ChoiceField(**kwargs)
  • Default widget: Select
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates that the given value exists in the list of choices.
  • Error message keys: required, invalid_choice

Takes one extra required argument:

ChoiceField.choices
An iterable (e.g., a list or tuple) of 2-tuples to use as choices for this field.

TypedChoiceField

class TypedChoiceField(**kwargs)

Just like a ChoiceField, except TypedChoiceField takes an extra coerce argument.

  • Default widget: Select
  • Empty value: Whatever you've given as empty_value
  • Normalizes to: the value returned by the coerce argument.
  • Validates that the given value exists in the list of choices.
  • Error message keys: required, invalid_choice

Takes extra arguments:

TypedChoiceField.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.
TypedChoiceField.empty_value
The value to use to represent "empty." Defaults to the empty string; None is another common choice here.

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:

DateField.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:

'%Y-%m-%d', '%m/%d/%Y', '%m/%d/%y', # '2006-10-25', '10/25/2006', '10/25/06'
'%b %d %Y', '%b %d, %Y',            # 'Oct 25 2006', 'Oct 25, 2006'
'%d %b %Y', '%d %b, %Y',            # '25 Oct 2006', '25 Oct, 2006'
'%B %d %Y', '%B %d, %Y',            # 'October 25 2006', 'October 25, 2006'
'%d %B %Y', '%d %B, %Y',            # '25 October 2006', '25 October, 2006'
Changed in Django 1.1: The DateField previously used a TextInput widget by default. It now uses a DateInput widget.

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:

DateTimeField.input_formats
A list of formats used to attempt to convert a string to a valid datetime.datetime object.

If no input_formats argument is provided, the default input formats are:

'%Y-%m-%d %H:%M:%S',     # '2006-10-25 14:30:59'
'%Y-%m-%d %H:%M',        # '2006-10-25 14:30'
'%Y-%m-%d',              # '2006-10-25'
'%m/%d/%Y %H:%M:%S',     # '10/25/2006 14:30:59'
'%m/%d/%Y %H:%M',        # '10/25/2006 14:30'
'%m/%d/%Y',              # '10/25/2006'
'%m/%d/%y %H:%M:%S',     # '10/25/06 14:30:59'
'%m/%d/%y %H:%M',        # '10/25/06 14:30'
'%m/%d/%y',              # '10/25/06'
Changed in Django 1.0: The DateTimeField used to use a TextInput widget by default. This has now changed.

DecimalField

New in Django 1.0: Please, see the release notes
class DecimalField(**kwargs)
  • Default widget: TextInput
  • Empty value: None
  • Normalizes to: A Python decimal.
  • Validates that the given value is a decimal. Leading and trailing whitespace is ignored.
  • Error message keys: required, invalid, max_value, min_value, max_digits, max_decimal_places, max_whole_digits

Takes four optional arguments:

DecimalField.max_value
DecimalField.min_value
These attributes define the limits for the fields value.
DecimalField.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.
DecimalField.decimal_places
The maximum number of decimal places permitted.

EmailField

class EmailField(**kwargs)
  • Default widget: TextInput
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates that the given value is a valid e-mail address, using a moderately complex regular expression.
  • Error message keys: required, invalid

Has two optional arguments for validation, max_length and min_length. If provided, these arguments ensure that the string is at most or at least the given length.

FileField

New in Django 1.0: Please, see the release notes
class FileField(**kwargs)
  • Default widget: FileInput
  • Empty value: None
  • Normalizes to: An UploadedFile object that wraps the file content and file name into a single object.
  • Validates that non-empty file data has been bound to the form.
  • Error message keys: required, invalid, missing, 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.

FilePathField

New in Django 1.0: Please, see the release notes
class FilePathField(**kwargs)
  • Default widget: Select
  • Empty value: None
  • Normalizes to: A unicode object
  • 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 three extra arguments; only path is required:

FilePathField.path
The absolute path to the directory whose contents you want listed. This directory must exist.
FilePathField.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.
FilePathField.match
A regular expression pattern; only files with names matching this expression will be allowed as choices.

FloatField

  • Default widget: TextInput
  • Empty value: None
  • Normalizes to: A Python float.
  • Validates that the given value is an float. Leading and trailing whitespace is allowed, as in Python's float() function.
  • Error message keys: 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.

ImageField

New in Django 1.0: Please, see the release notes
class ImageField(**kwargs)
  • Default widget: FileInput
  • 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, and that the file is of an image format understood by PIL.
  • Error message keys: required, invalid, missing, empty, invalid_image

Using an ImageField requires that the Python Imaging Library is installed.

When you use an ImageField on a form, you must also remember to bind the file data to the form.

IntegerField

class IntegerField(**kwargs)
  • Default widget: TextInput
  • Empty value: None
  • Normalizes to: A Python integer or long integer.
  • Validates that the given value is an integer. Leading and trailing whitespace is allowed, as in Python's int() function.
  • Error message keys: required, invalid, max_value, min_value

Takes two optional arguments for validation:

IntegerField.max_value
IntegerField.min_value
These control the range of values permitted in the field.

IPAddressField

class IPAddressField(**kwargs)
  • Default widget: TextInput
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates that the given value is a valid IPv4 address, using a regular expression.
  • Error message keys: required, invalid

MultipleChoiceField

class MultipleChoiceField(**kwargs)
  • Default widget: SelectMultiple
  • Empty value: [] (an empty list)
  • Normalizes to: A list of Unicode objects.
  • Validates that every value in the given list of values exists in the list of choices.
  • Error message keys: required, invalid_choice, invalid_list

Takes one extra 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).

RegexField

class RegexField(**kwargs)
  • Default widget: TextInput
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates that the given value matches against a certain regular expression.
  • Error message keys: required, invalid

Takes one required argument:

RegexField.regex
A regular expression specified either as a string or a compiled regular expression object.

Also takes max_length and min_length, which work just as they do for CharField.

The optional argument error_message is also accepted for backwards compatibility. The preferred way to provide an error message is to use the error_messages argument, passing a dictionary with 'invalid' as a key and the error message as the value.

TimeField

class TimeField(**kwargs)
  • Default widget: TextInput
  • 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:

TimeField.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:

'%H:%M:%S',     # '14:30:59'
'%H:%M',        # '14:30'

URLField

class URLField(**kwargs)
  • Default widget: TextInput
  • Empty value: '' (an empty string)
  • Normalizes to: A Unicode object.
  • Validates that the given value is a valid URL.
  • Error message keys: required, invalid, invalid_link

Takes the following optional arguments:

URLField.max_length
URLField.min_length
Same as CharField.max_length and CharField.min_length.
URLField.verify_exists
If True, the validator will attempt to load the given URL, raising ValidationError if the page gives a 404. Defaults to False.
URLField.validator_user_agent
String used as the user-agent used when checking for a URL's existence. Defaults to the value of the URL_VALIDATOR_USER_AGENT setting.

Slightly complex built-in Field classes

The following are not yet documented.

class ComboField(**kwargs)
class MultiValueField(**kwargs)
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

Takes two optional arguments:

SplitDateTimeField.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.

SplitDateTimeField.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.

Changed in Django 1.1: The SplitDateTimeField previously used two TextInput widgets by default. The input_date_formats and input_time_formats arguments are also new.

Fields which handle relationships

For representing relationships between models, two fields are provided which can derive their choices from a QuerySet:

class ModelChoiceField(**kwargs)
class ModelMultipleChoiceField(**kwargs)

These fields place one or more model objects into the cleaned_data dictionary of forms in which they're used. Both of these fields have an additional required argument:

ModelChoiceField.queryset
A QuerySet of model objects from which the choices for the field will be derived, and which will be used to validate the user's selection.

ModelChoiceField

Allows the selection of a single model object, suitable for representing a foreign key.

The __unicode__ 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:

class MyModelChoiceField(ModelChoiceField):
    def label_from_instance(self, obj):
        return "My Object #%i" % obj.id
ModelChoiceField.empty_label

By default the <select> widget used by ModelChoiceField will have a 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).

ModelMultipleChoiceField

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.

Creating custom fields

If the built-in Field classes don't meet your needs, you can easily create custom Field classes. To do this, just 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).

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