# documentación de Django - 1.10.7

# Widgets

A widget is Django’s representation of an 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.

Truco

Widgets should not be confused with the form 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 assigned to form fields.

## 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 Built-in Field classes.

However, if you want to use a different widget for a field, you can just use the `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 `Textarea` widget, rather than the default `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 `years` attribute is set for a `SelectDateWidget`:

    from django import forms

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

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

See the 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 `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 `Select` widget itself uses a `<select>` HTML list representation, while `RadioSelect` uses radio buttons.

`Select` widgets are used by default on `ChoiceField` fields. The choices displayed on the widget are inherited from the `ChoiceField` and changing `ChoiceField.choices` will update `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 `choices` attribute can however be used with fields which are not based on choice – such as a `CharField` – but it is recommended to use a `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 `TextInput` widgets will appear the same on your Web pages.

There are two ways to customize widgets: per widget instance and per widget class.

### 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 `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" required /></td></tr>
    <tr><th>Url:</th><td><input type="url" name="url" required /></td></tr>
    <tr><th>Comment:</th><td><input type="text" name="comment" required /></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 `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" required /></td></tr>
    <tr><th>Url:</th><td><input type="url" name="url" required /></td></tr>
    <tr><th>Comment:</th><td><input type="text" name="comment" size="40" required /></td></tr>

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

### 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 define a “Media” inner class or create a “media” property.

These methods involve somewhat advanced Python programming and are described in detail in the Form Assets topic guide.

## Base widget classes

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

### `Widget`

class `Widget`(attrs=None)

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

  `attrs`

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

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

    If you assign a value of `True` or `False` to an attribute, it will be rendered as an HTML5 boolean attribute:

        >>> name = forms.TextInput(attrs={'required': True})
        >>> name.render('name', 'A name')
        '<input name="name" type="text" value="A name" required />'
        >>>
        >>> name = forms.TextInput(attrs={'required': False})
        >>> name.render('name', 'A name')
        '<input name="name" type="text" value="A name" />'

  `supports_microseconds`

    An attribute that defaults to `True`. If set to `False`, the microseconds part of `datetime` and `time` values will be set to `0`.

    In older versions, this attribute was only defined on the date and time widgets (as `False`).

  `format_value`(value)

    Cleans and returns a value for use in the widget template. `value` isn’t guaranteed to be valid input, therefore subclass implementations should program defensively.

    In older versions, this method is a private API named `_format_value()`. The old name will work until Django 2.0.

  `id_for_label`(self, id_)

    Returns the HTML ID attribute of this widget for use by a `<label>`, given the ID of the field. Returns `None` if an ID isn’t available.

    This hook is necessary because some widgets have multiple HTML elements and, thus, multiple IDs. In that case, this method should return an ID value that corresponds to the first ID in the widget’s tags.

  `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.

  `value_from_datadict`(data, files, name)

    Given a dictionary of data and this widget’s name, returns the value of this widget. `files` may contain data coming from `request.FILES`. Returns `None` if a value wasn’t provided. Note also that `value_from_datadict` may be called more than once during handling of form data, so if you customize it and add expensive processing, you should implement some caching mechanism yourself.

  `value_omitted_from_data`(data, files, name)

    Given `data` and `files` dictionaries and this widget’s name, returns whether or not there’s data or files for the widget.

    The method’s result affects whether or not a field in a model form falls back to its default.

    Special cases are `CheckboxInput`, `CheckboxSelectMultiple`, and `SelectMultiple`, which always return `False` because an unchecked checkbox and unselected `<select multiple>` don’t appear in the data of an HTML form submission, so it’s unknown whether or not the user submitted a value.

  `use_required_attribute`(initial)

    Given a form field’s `initial` value, returns whether or not the widget can be rendered with the `required` HTML attribute. Forms use this method along with `Field.required` and `Form.use_required_attribute` to determine whether or not to display the `required` attribute for each field.

    By default, returns `False` for hidden widgets and `True` otherwise. Special cases are `ClearableFileInput`, which returns `False` when `initial` is not set, and `CheckboxSelectMultiple`, which always returns `False` because browser validation would require all checkboxes to be checked instead of at least one.

    Override this method in custom widgets that aren’t compatible with browser validation. For example, a WSYSIWG text editor widget backed by a hidden `textarea` element may want to always return `False` to avoid browser validation on the hidden field.

### `MultiWidget`

class `MultiWidget`(widgets, attrs=None)

  A widget that is composed of multiple widgets. `MultiWidget` works hand in hand with the `MultiValueField`.

  `MultiWidget` has one required argument:

  `widgets`

    An iterable containing the widgets needed.

  And one required 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 `SplitDateTimeWidget` turns a `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]

    Truco

    Note that `MultiValueField` has a complementary method `compress()` with the opposite responsibility - to combine cleaned values of all member fields into one.

  Other methods that may be useful to override include:

  `render`(name, value, attrs=None)

    Argument `value` is handled differently in this method from the subclasses of `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 `render()` will be a concatenation of rendered child widgets. If `value` is not a list, it will first be processed by the method `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 `render()` need not be implemented in the subclasses.

  `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 `MultiWidget` to display a date with the day, month, and year in different select boxes. This widget is intended to be used with a `DateField` rather than a `MultiValueField`, thus we have implemented `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 ''.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 `Select` widgets in a tuple. The `super` class uses this tuple to setup the widget.

  The `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 `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 `value_from_datadict()` returns a list of values corresponding to each `Widget`. This is appropriate when using a `MultiWidget` with a `MultiValueField`, but since we want to use this widget with a `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

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

### 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`

  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 `localize` property set to `True`.

#### `EmailInput`

class `EmailInput`

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

#### `URLInput`

class `URLInput`

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

#### `PasswordInput`

class `PasswordInput`

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

  Takes one optional argument:

  `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 `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 `TextInput`, with one more optional argument:

  `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 `DATE_INPUT_FORMATS` and respects Format localization.

#### `DateTimeInput`

class `DateTimeInput`

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

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

  `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 `DATETIME_INPUT_FORMATS` and respects Format localization.

  By default, the microseconds part of the time value is always set to `0`. If microseconds are required, use a subclass with the `supports_microseconds` attribute set to `True`.

#### `TimeInput`

class `TimeInput`

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

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

  `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 `TIME_INPUT_FORMATS` and respects Format localization.

  For the treatment of microseconds, see `DateTimeInput`.

#### `Textarea`

class `Textarea`

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

### Selector and checkbox widgets

#### `CheckboxInput`

class `CheckboxInput`

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

  Takes one optional argument:

  `check_test`

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

#### `Select`

class `Select`

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

#### `NullBooleanSelect`

class `NullBooleanSelect`

  Select widget with options ‘Unknown’, ‘Yes’ and ‘No’

#### `SelectMultiple`

class `SelectMultiple`

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

#### `RadioSelect`

class `RadioSelect`

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

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

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

  This would generate the following HTML:

      <div class="myradio">
          <label for="id_beatles_0"><input id="id_beatles_0" name="beatles" type="radio" value="john" required /> John</label>
      </div>
      <div class="myradio">
          <label for="id_beatles_1"><input id="id_beatles_1" name="beatles" type="radio" value="paul" required /> Paul</label>
      </div>
      <div class="myradio">
          <label for="id_beatles_2"><input id="id_beatles_2" name="beatles" type="radio" value="george" required /> George</label>
      </div>
      <div class="myradio">
          <label for="id_beatles_3"><input id="id_beatles_3" name="beatles" type="radio" value="ringo" required /> Ringo</label>
      </div>

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

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

  ...will result in the following HTML:

      <label for="id_beatles_0">
          John
          <span class="radio"><input id="id_beatles_0" name="beatles" type="radio" value="john" required /></span>
      </label>

      <label for="id_beatles_1">
          Paul
          <span class="radio"><input id="id_beatles_1" name="beatles" type="radio" value="paul" required /></span>
      </label>

      <label for="id_beatles_2">
          George
          <span class="radio"><input id="id_beatles_2" name="beatles" type="radio" value="george" required /></span>
      </label>

      <label for="id_beatles_3">
          Ringo
          <span class="radio"><input id="id_beatles_3" name="beatles" type="radio" value="ringo" required /></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.

  The outer `<ul>` container receives the `id` attribute of the widget, if defined, or `BoundField.auto_id` otherwise.

  When looping over the radio buttons, the `label` and `input` tags include `for` and `id` attributes, respectively. Each radio button has an `id_for_label` attribute to output the element’s ID.

#### `CheckboxSelectMultiple`

class `CheckboxSelectMultiple`

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

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

  The outer `<ul>` container receives the `id` attribute of the widget, if defined, or `BoundField.auto_id` otherwise.

Like `RadioSelect`, you can loop over the individual checkboxes for the widget’s choices. Unlike `RadioSelect`, the checkboxes won’t include the `required` HTML attribute if the field is required because browser validation would require all checkboxes to be checked instead of at least one.

When looping over the checkboxes, the `label` and `input` tags include `for` and `id` attributes, respectively. Each checkbox has an `id_for_label` attribute to output the element’s ID.

### 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

#### `MultipleHiddenInput`

class `MultipleHiddenInput`

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

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

  `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 `Field`.

#### `SplitDateTimeWidget`

class `SplitDateTimeWidget`

  Wrapper (using `MultiWidget`) around two widgets: `DateInput` for the date, and `TimeInput` for the time. Must be used with `SplitDateTimeField` rather than `DateTimeField`.

  `SplitDateTimeWidget` has two optional attributes:

  `date_format`

    Similar to `DateInput.format`

  `time_format`

    Similar to `TimeInput.format`

#### `SplitHiddenDateTimeWidget`

class `SplitHiddenDateTimeWidget`

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

#### `SelectDateWidget`

class `SelectDateWidget`

  Wrapper around three `Select` widgets: one each for month, day, and year.

  Takes several optional arguments:

  `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.

  `months`

    An optional dict of months to use in the “months” select box.

    The keys of the dict correspond to the month number (1-indexed) and the values are the displayed months:

        MONTHS = {
            1:_('jan'), 2:_('feb'), 3:_('mar'), 4:_('apr'),
            5:_('may'), 6:_('jun'), 7:_('jul'), 8:_('aug'),
            9:_('sep'), 10:_('oct'), 11:_('nov'), 12:_('dec')
        }

  `empty_label`

    If the `DateField` is not required, `SelectDateWidget` will have an empty choice at the top of the list (which is `---` by default). You can change the text of this label with the `empty_label` attribute. `empty_label` can be a `string`, `list`, or `tuple`. When a string is used, all select boxes will each have an empty choice with this label. If `empty_label` is a `list` or `tuple` of 3 string elements, the select boxes will have their own custom label. The labels should be in this order `('year_label', 'month_label', 'day_label')`.

        # A custom empty label with string
        field1 = forms.DateField(widget=SelectDateWidget(empty_label="Nothing"))

        # A custom empty label with tuple
        field1 = forms.DateField(
            widget=SelectDateWidget(
                empty_label=("Choose Year", "Choose Month", "Choose Day"),
            ),
        )

  This widget used to be located in the `django.forms.extras.widgets` package. It is now defined in `django.forms.widgets` and like the other widgets it can be imported directly from `django.forms`.