django1/docs/ref/forms/widgets.txt

=======
Widgets
=======

.. module:: django.forms.widgets
   :synopsis: Django's built-in form widgets.

.. currentmodule:: django.forms

A widget is Django's representation of a HTML input element. The widget
handles the rendering of the HTML, and the extraction of data from a GET/POST
dictionary that corresponds to the widget.

.. tip::

    Widgets should not be confused with the :doc:`form fields </ref/forms/fields>`.
    Form fields deal with the logic of input validation and are used directly
    in templates. Widgets deal with rendering of HTML form input elements on
    the web page and extraction of raw submitted data. However, widgets do
    need to be :ref:`assigned <widget-to-field>` to form fields.

.. _widget-to-field:

Specifying widgets
------------------

Whenever you specify a field on a form, Django will use a default widget
that is appropriate to the type of data that is to be displayed. To find
which widget is used on which field, see the documentation about
:ref:`built-in fields`.

However, if you want to use a different widget for a field, you can
just use the :attr:`~Field.widget` argument on the field definition. For
example::

    from django import forms

    class CommentForm(forms.Form):
        name = forms.CharField()
        url = forms.URLField()
        comment = forms.CharField(widget=forms.Textarea)

This would specify a form with a comment that uses a larger :class:`Textarea`
widget, rather than the default :class:`TextInput` widget.


Setting arguments for widgets
-----------------------------

Many widgets have optional extra arguments; they can be set when defining the
widget on the field. In the following example, the
:attr:`~django.forms.extras.widgets.SelectDateWidget.years` attribute is set
for a :class:`~django.forms.extras.widgets.SelectDateWidget`::

    from django import forms
    from django.forms.extras.widgets import SelectDateWidget

    BIRTH_YEAR_CHOICES = ('1980', '1981', '1982')
    FAVORITE_COLORS_CHOICES = (('blue', 'Blue'),
                                ('green', 'Green'),
                                ('black', 'Black'))

    class SimpleForm(forms.Form):
        birth_year = forms.DateField(widget=SelectDateWidget(years=BIRTH_YEAR_CHOICES))
        favorite_colors = forms.MultipleChoiceField(required=False,
            widget=forms.CheckboxSelectMultiple, choices=FAVORITE_COLORS_CHOICES)

See the :ref:`built-in widgets` for more information about which widgets
are available and which arguments they accept.


Widgets inheriting from the Select widget
-----------------------------------------

Widgets inheriting from the :class:`Select` widget deal with choices. They
present the user with a list of options to choose from. The different widgets
present this choice differently; the :class:`Select` widget itself uses a
``<select>`` HTML list representation, while :class:`RadioSelect` uses radio
buttons.

:class:`Select` widgets are used by default on :class:`ChoiceField` fields. The
choices displayed on the widget are inherited from the :class:`ChoiceField` and
changing :attr:`ChoiceField.choices` will update :attr:`Select.choices`. For
example::

    >>> from django import forms
    >>> CHOICES = (('1', 'First',), ('2', 'Second',))
    >>> choice_field = forms.ChoiceField(widget=forms.RadioSelect, choices=CHOICES)
    >>> choice_field.choices
    [('1', 'First'), ('2', 'Second')]
    >>> choice_field.widget.choices
    [('1', 'First'), ('2', 'Second')]
    >>> choice_field.widget.choices = ()
    >>> choice_field.choices = (('1', 'First and only',),)
    >>> choice_field.widget.choices
    [('1', 'First and only')]


Widgets which offer a :attr:`~Select.choices` attribute can however be used
with fields which are not based on choice -- such as a :class:`CharField` --
but it is recommended to use a :class:`ChoiceField`-based field when the
choices are inherent to the model and not just the representational widget.

Customizing widget instances
----------------------------

When Django renders a widget as HTML, it only renders very minimal markup -
Django doesn't add class names, or any other widget-specific attributes. This
means, for example, that all :class:`TextInput` widgets will appear the same
on your Web pages.

There are two ways to customize widgets: :ref:`per widget instance
<styling-widget-instances>` and :ref:`per widget class <styling-widget-classes>`.

.. _styling-widget-instances:

Styling widget instances
^^^^^^^^^^^^^^^^^^^^^^^^

If you want to make one widget instance look different from another, you will
need to specify additional attributes at the time when the widget object is
instantiated and assigned to a form field (and perhaps add some rules to your
CSS files).

For example, take the following simple form::

    from django import forms

    class CommentForm(forms.Form):
        name = forms.CharField()
        url = forms.URLField()
        comment = forms.CharField()

This form will include three default :class:`TextInput` widgets, with default
rendering -- no CSS class, no extra attributes. This means that the input boxes
provided for each widget will be rendered exactly the same::

    >>> f = CommentForm(auto_id=False)
    >>> f.as_table()
    <tr><th>Name:</th><td><input type="text" name="name" /></td></tr>
    <tr><th>Url:</th><td><input type="url" name="url"/></td></tr>
    <tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>

On a real Web page, you probably don't want every widget to look the same. You
might want a larger input element for the comment, and you might want the
'name' widget to have some special CSS class. It is also possible to specify
the 'type' attribute to take advantage of the new HTML5 input types.  To do
this, you use the :attr:`Widget.attrs` argument when creating the widget::

    class CommentForm(forms.Form):
        name = forms.CharField(
                    widget=forms.TextInput(attrs={'class':'special'}))
        url = forms.URLField()
        comment = forms.CharField(
                   widget=forms.TextInput(attrs={'size':'40'}))

Django will then include the extra attributes in the rendered output:

    >>> f = CommentForm(auto_id=False)
    >>> f.as_table()
    <tr><th>Name:</th><td><input type="text" name="name" class="special"/></td></tr>
    <tr><th>Url:</th><td><input type="url" name="url"/></td></tr>
    <tr><th>Comment:</th><td><input type="text" name="comment" size="40"/></td></tr>

You can also set the HTML ``id`` using :attr:`~Widget.attrs`. See
:attr:`BoundField.id_for_label` for an example.

.. _styling-widget-classes:

Styling widget classes
^^^^^^^^^^^^^^^^^^^^^^

With widgets, it is possible to add assets (``css`` and ``javascript``)
and more deeply customize their appearance and behavior.

In a nutshell, you will need to subclass the widget and either
:ref:`define a "Media" inner class  <assets-as-a-static-definition>` or
:ref:`create a "media" property <dynamic-property>`.

These methods involve somewhat advanced Python programming and are described in
detail in the :doc:`Form Assets </topics/forms/media>` topic guide.

.. _base-widget-classes:

Base Widget classes
-------------------

Base widget classes :class:`Widget` and :class:`MultiWidget` are subclassed by
all the :ref:`built-in widgets <built-in widgets>` and may serve as a
foundation for custom widgets.

.. class:: Widget(attrs=None)

    This abstract class cannot be rendered, but provides the basic attribute
    :attr:`~Widget.attrs`.  You may also implement or override the
    :meth:`~Widget.render()` method on custom widgets.

    .. attribute:: Widget.attrs

        A dictionary containing HTML attributes to be set on the rendered
        widget.

        .. code-block:: python

            >>> from django import forms
            >>> name = forms.TextInput(attrs={'size': 10, 'title': 'Your name',})
            >>> name.render('name', 'A name')
            u'<input title="Your name" type="text" name="name" value="A name" size="10" />'

    .. method:: render(name, value, attrs=None)

        Returns HTML for the widget, as a Unicode string. This method must be
        implemented by the subclass, otherwise ``NotImplementedError`` will be
        raised.

        The 'value' given is not guaranteed to be valid input, therefore
        subclass implementations should program defensively.

    .. method:: value_from_datadict(self, data, files, name)

        Given a dictionary of data and this widget's name, returns the value
        of this widget. Returns ``None`` if a value wasn't provided.

.. class:: MultiWidget(widgets, attrs=None)

    A widget that is composed of multiple widgets.
    :class:`~django.forms.MultiWidget` works hand in hand with the
    :class:`~django.forms.MultiValueField`.

    :class:`MultiWidget` has one required argument:

    .. attribute:: MultiWidget.widgets

        An iterable containing the widgets needed.

    And one required method:

    .. method:: decompress(value)

        This method takes a single "compressed" value from the field and
        returns a list of "decompressed" values. The input value can be
        assumed valid, but not necessarily non-empty.

        This method **must be implemented** by the subclass, and since the
        value may be empty, the implementation must be defensive.

        The rationale behind "decompression" is that it is necessary to "split"
        the combined value of the form field into the values for each widget.

        An example of this is how :class:`SplitDateTimeWidget` turns a
        :class:`~datetime.datetime` value into a list with date and time split
        into two separate values::

            from django.forms import MultiWidget

            class SplitDateTimeWidget(MultiWidget):

                # ...

                def decompress(self, value):
                    if value:
                        return [value.date(), value.time().replace(microsecond=0)]
                    return [None, None]

        .. tip::

            Note that :class:`~django.forms.MultiValueField` has a
            complementary method :meth:`~django.forms.MultiValueField.compress`
            with the opposite responsibility - to combine cleaned values of
            all member fields into one.

    Other methods that may be useful to override include:

    .. method:: render(name, value, attrs=None)

        Argument ``value`` is handled differently in this method from the
        subclasses of :class:`~Widget` because it has to figure out how to
        split a single value for display in multiple widgets.

        The ``value`` argument used when rendering can be one of two things:

        * A ``list``.
        * A single value (e.g., a string) that is the "compressed" representation
          of a ``list`` of values.

        If ``value`` is a list, the output of :meth:`~MultiWidget.render` will
        be a concatenation of rendered child widgets. If ``value`` is not a
        list, it will first be processed by the method
        :meth:`~MultiWidget.decompress()` to create the list and then rendered.

        When ``render()`` executes its HTML rendering, each value in the list
        is rendered with the corresponding widget -- the first value is
        rendered in the first widget, the second value is rendered in the
        second widget, etc.

        Unlike in the single value widgets, method :meth:`~MultiWidget.render`
        need not be implemented in the subclasses.

    .. method:: format_output(rendered_widgets)

        Given a list of rendered widgets (as strings), returns a Unicode string
        representing the HTML for the whole lot.

        This hook allows you to format the HTML design of the widgets any way
        you'd like.

    Here's an example widget which subclasses :class:`MultiWidget` to display
    a date with the day, month, and year in different select boxes. This widget
    is intended to be used with a :class:`~django.forms.DateField` rather than
    a :class:`~django.forms.MultiValueField`, thus we have implemented
    :meth:`~Widget.value_from_datadict`::

        from datetime import date
        from django.forms import widgets

        class DateSelectorWidget(widgets.MultiWidget):
            def __init__(self, attrs=None):
                # create choices for days, months, years
                # example below, the rest snipped for brevity.
                years = [(year, year) for year in (2011, 2012, 2013)]
                _widgets = (
                    widgets.Select(attrs=attrs, choices=days),
                    widgets.Select(attrs=attrs, choices=months),
                    widgets.Select(attrs=attrs, choices=years),
                )
                super(DateSelectorWidget, self).__init__(_widgets, attrs)

            def decompress(self, value):
                if value:
                    return [value.day, value.month, value.year]
                return [None, None, None]

            def format_output(self, rendered_widgets):
                return u''.join(rendered_widgets)

            def value_from_datadict(self, data, files, name):
                datelist = [
                    widget.value_from_datadict(data, files, name + '_%s' % i)
                    for i, widget in enumerate(self.widgets)]
                try:
                    D = date(day=int(datelist[0]), month=int(datelist[1]),
                            year=int(datelist[2]))
                except ValueError:
                    return ''
                else:
                    return str(D)

    The constructor creates several :class:`Select` widgets in a tuple. The
    ``super`` class uses this tuple to setup the widget.

    The :meth:`~MultiWidget.format_output` method is fairly vanilla here (in
    fact, it's the same as what's been implemented as the default for
    ``MultiWidget``), but the idea is that you could add custom HTML between
    the widgets should you wish.

    The required method :meth:`~MultiWidget.decompress` breaks up a
    ``datetime.date`` value into the day, month, and year values corresponding
    to each widget. Note how the method handles the case where ``value`` is
    ``None``.

    The default implementation of :meth:`~Widget.value_from_datadict` returns
    a list of values corresponding to each ``Widget``.  This is appropriate
    when using a ``MultiWidget`` with a :class:`~django.forms.MultiValueField`,
    but since we want to use this widget with a :class:`~django.forms.DateField`
    which takes a single value, we have overridden this method to combine the
    data of all the subwidgets into a ``datetime.date``. The method extracts
    data from the ``POST`` dictionary and constructs and validates the date.
    If it is valid, we return the string, otherwise, we return an empty string
    which will cause ``form.is_valid`` to return ``False``.

.. _built-in widgets:

Built-in widgets
----------------

Django provides a representation of all the basic HTML widgets, plus some
commonly used groups of widgets in the ``django.forms.widgets`` module,
including :ref:`the input of text <text-widgets>`, :ref:`various checkboxes
and selectors <selector-widgets>`, :ref:`uploading files <file-upload-widgets>`,
and :ref:`handling of multi-valued input <composite-widgets>`.

.. _text-widgets:

Widgets handling input of text
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

These widgets make use of the HTML elements ``input`` and ``textarea``.

``TextInput``
~~~~~~~~~~~~~

.. class:: TextInput

    Text input: ``<input type="text" ...>``

``NumberInput``
~~~~~~~~~~~~~~~

.. class:: NumberInput

    .. versionadded:: 1.6

    Text input: ``<input type="number" ...>``

    Beware that not all browsers support entering localized numbers in
    ``number`` input types. Django itself avoids using them for fields having
    their :attr:`~django.forms.Field.localize` property to ``True``.

``EmailInput``
~~~~~~~~~~~~~~

.. class:: EmailInput

    .. versionadded:: 1.6

    Text input: ``<input type="email" ...>``

``URLInput``
~~~~~~~~~~~~

.. class:: URLInput

    .. versionadded:: 1.6

    Text input: ``<input type="url" ...>``

``PasswordInput``
~~~~~~~~~~~~~~~~~

.. class:: PasswordInput

    Password input: ``<input type='password' ...>``

    Takes one optional argument:

    .. attribute:: PasswordInput.render_value

        Determines whether the widget will have a value filled in when the
        form is re-displayed after a validation error (default is ``False``).

``HiddenInput``
~~~~~~~~~~~~~~~

.. class:: HiddenInput

    Hidden input: ``<input type='hidden' ...>``

    Note that there also is a :class:`MultipleHiddenInput` widget that
    encapsulates a set of hidden input elements.

``DateInput``
~~~~~~~~~~~~~

.. class:: DateInput

    Date input as a simple text box: ``<input type='text' ...>``

    Takes same arguments as :class:`TextInput`, with one more optional argument:

    .. attribute:: DateInput.format

        The format in which this field's initial value will be displayed.

    If no ``format`` argument is provided, the default format is the first
    format found in :setting:`DATE_INPUT_FORMATS` and respects
    :ref:`format-localization`.

``DateTimeInput``
~~~~~~~~~~~~~~~~~

.. class:: DateTimeInput

    Date/time input as a simple text box: ``<input type='text' ...>``

    Takes same arguments as :class:`TextInput`, with one more optional argument:

    .. attribute:: DateTimeInput.format

        The format in which this field's initial value will be displayed.

    If no ``format`` argument is provided, the default format is the first
    format found in :setting:`DATETIME_INPUT_FORMATS` and respects
    :ref:`format-localization`.

``TimeInput``
~~~~~~~~~~~~~

.. class:: TimeInput

    Time input as a simple text box: ``<input type='text' ...>``

    Takes same arguments as :class:`TextInput`, with one more optional argument:

    .. attribute:: TimeInput.format

        The format in which this field's initial value will be displayed.

    If no ``format`` argument is provided, the default format is the first
    format found in :setting:`TIME_INPUT_FORMATS` and respects
    :ref:`format-localization`.

``Textarea``
~~~~~~~~~~~~

.. class:: Textarea

    Text area: ``<textarea>...</textarea>``

.. _selector-widgets:

Selector and checkbox widgets
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

``CheckboxInput``
~~~~~~~~~~~~~~~~~

.. class:: CheckboxInput

    Checkbox: ``<input type='checkbox' ...>``

    Takes one optional argument:

    .. attribute:: CheckboxInput.check_test

        A callable that takes the value of the CheckBoxInput and returns
        ``True`` if the checkbox should be checked for that value.

        .. versionchanged:: 1.5

            Exceptions from ``check_test`` used to be silenced by its caller,
            this is no longer the case, they will propagate upwards.

``Select``
~~~~~~~~~~

.. class:: Select

    Select widget: ``<select><option ...>...</select>``

    .. attribute:: Select.choices

        This attribute is optional when the form field does not have a
        ``choices`` attribute. If it does, it will override anything you set
        here when the attribute is updated on the :class:`Field`.

``NullBooleanSelect``
~~~~~~~~~~~~~~~~~~~~~

.. class:: NullBooleanSelect

    Select widget with options 'Unknown', 'Yes' and 'No'

``SelectMultiple``
~~~~~~~~~~~~~~~~~~

.. class:: SelectMultiple

    Similar to :class:`Select`, but allows multiple selection:
    ``<select multiple='multiple'>...</select>``

``RadioSelect``
~~~~~~~~~~~~~~~

.. class:: RadioSelect

    Similar to :class:`Select`, but rendered as a list of radio buttons within
    ``<li>`` tags:

    .. code-block:: html

        <ul>
          <li><input type='radio' ...></li>
          ...
        </ul>

    For more granular control over the generated markup, you can loop over the
    radio buttons in the template. Assuming a form ``myform`` with a field
    ``beatles`` that uses a ``RadioSelect`` as its widget:

    .. code-block:: html+django

        {% for radio in myform.beatles %}
        <div class="myradio">
            {{ radio }}
        </div>
        {% endfor %}

    This would generate the following HTML:

    .. code-block:: html

        <div class="myradio">
            <label><input type="radio" name="beatles" value="john" /> John</label>
        </div>
        <div class="myradio">
            <label><input type="radio" name="beatles" value="paul" /> Paul</label>
        </div>
        <div class="myradio">
            <label><input type="radio" name="beatles" value="george" /> George</label>
        </div>
        <div class="myradio">
            <label><input type="radio" name="beatles" value="ringo" /> Ringo</label>
        </div>

    That included the ``<label>`` tags. To get more granular, you can use each
    radio button's ``tag`` and ``choice_label`` attributes. For example, this template...

    .. code-block:: html+django

        {% for radio in myform.beatles %}
            <label>
                {{ radio.choice_label }}
                <span class="radio">{{ radio.tag }}</span>
            </label>
        {% endfor %}

    ...will result in the following HTML:

    .. code-block:: html

            <label>
                John
                <span class="radio"><input type="radio" name="beatles" value="john" /></span>
            </label>
            <label>
                Paul
                <span class="radio"><input type="radio" name="beatles" value="paul" /></span>
            </label>
            <label>
                George
                <span class="radio"><input type="radio" name="beatles" value="george" /></span>
            </label>
            <label>
                Ringo
                <span class="radio"><input type="radio" name="beatles" value="ringo" /></span>
            </label>

    If you decide not to loop over the radio buttons -- e.g., if your template simply includes
    ``{{ myform.beatles }}`` -- they'll be output in a ``<ul>`` with ``<li>`` tags, as above.

.. versionchanged:: 1.6

The outer ``<ul>`` container will now receive the ``id`` attribute defined on
the widget.

``CheckboxSelectMultiple``
~~~~~~~~~~~~~~~~~~~~~~~~~~

.. class:: CheckboxSelectMultiple

    Similar to :class:`SelectMultiple`, but rendered as a list of check
    buttons:

    .. code-block:: html

        <ul>
          <li><input type='checkbox' ...></li>
          ...
        </ul>

.. versionchanged:: 1.6

The outer ``<ul>`` container will now receive the ``id`` attribute defined on
the widget.

Like :class:`RadioSelect`, you can now loop over the individual checkboxes making
up the lists. See the documentation of :class:`RadioSelect` for more details.

.. _file-upload-widgets:

File upload widgets
^^^^^^^^^^^^^^^^^^^

``FileInput``
~~~~~~~~~~~~~

.. class:: FileInput

    File upload input: ``<input type='file' ...>``

``ClearableFileInput``
~~~~~~~~~~~~~~~~~~~~~~

.. class:: ClearableFileInput

    File upload input: ``<input type='file' ...>``, with an additional checkbox
    input to clear the field's value, if the field is not required and has
    initial data.

.. _composite-widgets:

Composite widgets
^^^^^^^^^^^^^^^^^

``MultipleHiddenInput``
~~~~~~~~~~~~~~~~~~~~~~~

.. class:: MultipleHiddenInput

    Multiple ``<input type='hidden' ...>`` widgets.

    A widget that handles multiple hidden widgets for fields that have a list
    of values.

    .. attribute:: MultipleHiddenInput.choices

        This attribute is optional when the form field does not have a
        ``choices`` attribute. If it does, it will override anything you set
        here when the attribute is updated on the :class:`Field`.

``SplitDateTimeWidget``
~~~~~~~~~~~~~~~~~~~~~~~

.. class:: SplitDateTimeWidget

    Wrapper (using :class:`MultiWidget`) around two widgets: :class:`DateInput`
    for the date, and :class:`TimeInput` for the time.

    ``SplitDateTimeWidget`` has two optional attributes:

    .. attribute:: SplitDateTimeWidget.date_format

        Similar to :attr:`DateInput.format`

    .. attribute:: SplitDateTimeWidget.time_format

        Similar to :attr:`TimeInput.format`

``SplitHiddenDateTimeWidget``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. class:: SplitHiddenDateTimeWidget

    Similar to :class:`SplitDateTimeWidget`, but uses :class:`HiddenInput` for
    both date and time.

.. currentmodule:: django.forms.extras.widgets

``SelectDateWidget``
~~~~~~~~~~~~~~~~~~~~

.. class:: SelectDateWidget

    Wrapper around three :class:`~django.forms.Select` widgets: one each for
    month, day, and year. Note that this widget lives in a separate file from
    the standard widgets.

    Takes one optional argument:

    .. attribute:: SelectDateWidget.years

        An optional list/tuple of years to use in the "year" select box.
        The default is a list containing the current year and the next 9 years.