# Django 2.1.8.dev20190330215650 documentation

# Source code for django.forms.widgets

    """
    HTML Widget classes
    """

    import copy
    import datetime
    import re
    import warnings
    from itertools import chain

    from django.conf import settings
    from django.forms.utils import to_current_timezone
    from django.templatetags.static import static
    from django.utils import datetime_safe, formats
    from django.utils.dates import MONTHS
    from django.utils.formats import get_format
    from django.utils.html import format_html, html_safe
    from django.utils.safestring import mark_safe
    from django.utils.translation import gettext_lazy as _

    from .renderers import get_default_renderer

    __all__ = (
        'Media', 'MediaDefiningClass', 'Widget', 'TextInput', 'NumberInput',
        'EmailInput', 'URLInput', 'PasswordInput', 'HiddenInput',
        'MultipleHiddenInput', 'FileInput', 'ClearableFileInput', 'Textarea',
        'DateInput', 'DateTimeInput', 'TimeInput', 'CheckboxInput', 'Select',
        'NullBooleanSelect', 'SelectMultiple', 'RadioSelect',
        'CheckboxSelectMultiple', 'MultiWidget', 'SplitDateTimeWidget',
        'SplitHiddenDateTimeWidget', 'SelectDateWidget',
    )

    MEDIA_TYPES = ('css', 'js')

    class MediaOrderConflictWarning(RuntimeWarning):
        pass

    @html_safe
    class Media:
        def __init__(self, media=None, css=None, js=None):
            if media is not None:
                css = getattr(media, 'css', {})
                js = getattr(media, 'js', [])
            else:
                if css is None:
                    css = {}
                if js is None:
                    js = []
            self._css = css
            self._js = js

        def __repr__(self):
            return 'Media(css=%r, js=%r)' % (self._css, self._js)

        def __str__(self):
            return self.render()

        def render(self):
            return mark_safe('\n'.join(chain.from_iterable(getattr(self, 'render_' + name)() for name in MEDIA_TYPES)))

        def render_js(self):
            return [
                format_html(
                    '<script type="text/javascript" src="{}"></script>',
                    self.absolute_path(path)
                ) for path in self._js
            ]

        def render_css(self):
            # To keep rendering order consistent, we can't just iterate over items().
            # We need to sort the keys, and iterate over the sorted list.
            media = sorted(self._css)
            return chain.from_iterable([
                format_html(
                    '<link href="{}" type="text/css" media="{}" rel="stylesheet">',
                    self.absolute_path(path), medium
                ) for path in self._css[medium]
            ] for medium in media)

        def absolute_path(self, path):
            """
            Given a relative or absolute path to a static asset, return an absolute
            path. An absolute path will be returned unchanged while a relative path
            will be passed to django.templatetags.static.static().
            """
            if path.startswith(('http://', 'https://', '/')):
                return path
            return static(path)

        def __getitem__(self, name):
            """Return a Media object that only contains media of the given type."""
            if name in MEDIA_TYPES:
                return Media(**{str(name): getattr(self, '_' + name)})
            raise KeyError('Unknown media type "%s"' % name)

        @staticmethod
        def merge(list_1, list_2):
            """
            Merge two lists while trying to keep the relative order of the elements.
            Warn if the lists have the same two elements in a different relative
            order.

            For static assets it can be important to have them included in the DOM
            in a certain order. In JavaScript you may not be able to reference a
            global or in CSS you might want to override a style.
            """
            # Start with a copy of list_1.
            combined_list = list(list_1)
            last_insert_index = len(list_1)
            # Walk list_2 in reverse, inserting each element into combined_list if
            # it doesn't already exist.
            for path in reversed(list_2):
                try:
                    # Does path already exist in the list?
                    index = combined_list.index(path)
                except ValueError:
                    # Add path to combined_list since it doesn't exist.
                    combined_list.insert(last_insert_index, path)
                else:
                    if index > last_insert_index:
                        warnings.warn(
                            'Detected duplicate Media files in an opposite order:\n'
                            '%s\n%s' % (combined_list[last_insert_index], combined_list[index]),
                            MediaOrderConflictWarning,
                        )
                    # path already exists in the list. Update last_insert_index so
                    # that the following elements are inserted in front of this one.
                    last_insert_index = index
            return combined_list

        def __add__(self, other):
            combined = Media()
            combined._js = self.merge(self._js, other._js)
            combined._css = {
                medium: self.merge(self._css.get(medium, []), other._css.get(medium, []))
                for medium in self._css.keys() | other._css.keys()
            }
            return combined

    def media_property(cls):
        def _media(self):
            # Get the media property of the superclass, if it exists
            sup_cls = super(cls, self)
            try:
                base = sup_cls.media
            except AttributeError:
                base = Media()

            # Get the media definition for this class
            definition = getattr(cls, 'Media', None)
            if definition:
                extend = getattr(definition, 'extend', True)
                if extend:
                    if extend is True:
                        m = base
                    else:
                        m = Media()
                        for medium in extend:
                            m = m + base[medium]
                    return m + Media(definition)
                return Media(definition)
            return base
        return property(_media)

    class MediaDefiningClass(type):
        """
        Metaclass for classes that can have media definitions.
        """
        def __new__(mcs, name, bases, attrs):
            new_class = super(MediaDefiningClass, mcs).__new__(mcs, name, bases, attrs)

            if 'media' not in attrs:
                new_class.media = media_property(new_class)

            return new_class

    class Widget(metaclass=MediaDefiningClass):
        needs_multipart_form = False  # Determines does this widget need multipart form
        is_localized = False
        is_required = False
        supports_microseconds = True

        def __init__(self, attrs=None):
            self.attrs = {} if attrs is None else attrs.copy()

        def __deepcopy__(self, memo):
            obj = copy.copy(self)
            obj.attrs = self.attrs.copy()
            memo[id(self)] = obj
            return obj

        @property
        def is_hidden(self):
            return self.input_type == 'hidden' if hasattr(self, 'input_type') else False

        def subwidgets(self, name, value, attrs=None):
            context = self.get_context(name, value, attrs)
            yield context['widget']

        def format_value(self, value):
            """
            Return a value as it should appear when rendered in a template.
            """
            if value == '' or value is None:
                return None
            if self.is_localized:
                return formats.localize_input(value)
            return str(value)

        def get_context(self, name, value, attrs):
            context = {}
            context['widget'] = {
                'name': name,
                'is_hidden': self.is_hidden,
                'required': self.is_required,
                'value': self.format_value(value),
                'attrs': self.build_attrs(self.attrs, attrs),
                'template_name': self.template_name,
            }
            return context

        def render(self, name, value, attrs=None, renderer=None):
            """Render the widget as an HTML string."""
            context = self.get_context(name, value, attrs)
            return self._render(self.template_name, context, renderer)

        def _render(self, template_name, context, renderer=None):
            if renderer is None:
                renderer = get_default_renderer()
            return mark_safe(renderer.render(template_name, context))

        def build_attrs(self, base_attrs, extra_attrs=None):
            """Build an attribute dictionary."""
            return {**base_attrs, **(extra_attrs or {})}

        def value_from_datadict(self, data, files, name):
            """
            Given a dictionary of data and this widget's name, return the value
            of this widget or None if it's not provided.
            """
            return data.get(name)

        def value_omitted_from_data(self, data, files, name):
            return name not in data

        def id_for_label(self, id_):
            """
            Return the HTML ID attribute of this Widget for use by a <label>,
            given the ID of the field. Return None if no ID is 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.
            """
            return id_

        def use_required_attribute(self, initial):
            return not self.is_hidden

    class Input(Widget):
        """
        Base class for all <input> widgets.
        """
        input_type = None  # Subclasses must define this.
        template_name = 'django/forms/widgets/input.html'

        def __init__(self, attrs=None):
            if attrs is not None:
                attrs = attrs.copy()
                self.input_type = attrs.pop('type', self.input_type)
            super().__init__(attrs)

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            context['widget']['type'] = self.input_type
            return context

    class TextInput(Input):
        input_type = 'text'
        template_name = 'django/forms/widgets/text.html'

    class NumberInput(Input):
        input_type = 'number'
        template_name = 'django/forms/widgets/number.html'

    class EmailInput(Input):
        input_type = 'email'
        template_name = 'django/forms/widgets/email.html'

    class URLInput(Input):
        input_type = 'url'
        template_name = 'django/forms/widgets/url.html'

    class PasswordInput(Input):
        input_type = 'password'
        template_name = 'django/forms/widgets/password.html'

        def __init__(self, attrs=None, render_value=False):
            super().__init__(attrs)
            self.render_value = render_value

        def get_context(self, name, value, attrs):
            if not self.render_value:
                value = None
            return super().get_context(name, value, attrs)

    class HiddenInput(Input):
        input_type = 'hidden'
        template_name = 'django/forms/widgets/hidden.html'

    class MultipleHiddenInput(HiddenInput):
        """
        Handle <input type="hidden"> for fields that have a list
        of values.
        """
        template_name = 'django/forms/widgets/multiple_hidden.html'

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            final_attrs = context['widget']['attrs']
            id_ = context['widget']['attrs'].get('id')

            subwidgets = []
            for index, value_ in enumerate(context['widget']['value']):
                widget_attrs = final_attrs.copy()
                if id_:
                    # An ID attribute was given. Add a numeric index as a suffix
                    # so that the inputs don't all have the same ID attribute.
                    widget_attrs['id'] = '%s_%s' % (id_, index)
                widget = HiddenInput()
                widget.is_required = self.is_required
                subwidgets.append(widget.get_context(name, value_, widget_attrs)['widget'])

            context['widget']['subwidgets'] = subwidgets
            return context

        def value_from_datadict(self, data, files, name):
            try:
                getter = data.getlist
            except AttributeError:
                getter = data.get
            return getter(name)

        def format_value(self, value):
            return [] if value is None else value

    class FileInput(Input):
        input_type = 'file'
        needs_multipart_form = True
        template_name = 'django/forms/widgets/file.html'

        def format_value(self, value):
            """File input never renders a value."""
            return

        def value_from_datadict(self, data, files, name):
            "File widgets take data from FILES, not POST"
            return files.get(name)

        def value_omitted_from_data(self, data, files, name):
            return name not in files

    FILE_INPUT_CONTRADICTION = object()

    class ClearableFileInput(FileInput):
        clear_checkbox_label = _('Clear')
        initial_text = _('Currently')
        input_text = _('Change')
        template_name = 'django/forms/widgets/clearable_file_input.html'

        def clear_checkbox_name(self, name):
            """
            Given the name of the file input, return the name of the clear checkbox
            input.
            """
            return name + '-clear'

        def clear_checkbox_id(self, name):
            """
            Given the name of the clear checkbox input, return the HTML id for it.
            """
            return name + '_id'

        def is_initial(self, value):
            """
            Return whether value is considered to be initial value.
            """
            return bool(value and getattr(value, 'url', False))

        def format_value(self, value):
            """
            Return the file object if it has a defined url attribute.
            """
            if self.is_initial(value):
                return value

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            checkbox_name = self.clear_checkbox_name(name)
            checkbox_id = self.clear_checkbox_id(checkbox_name)
            context['widget'].update({
                'checkbox_name': checkbox_name,
                'checkbox_id': checkbox_id,
                'is_initial': self.is_initial(value),
                'input_text': self.input_text,
                'initial_text': self.initial_text,
                'clear_checkbox_label': self.clear_checkbox_label,
            })
            return context

        def value_from_datadict(self, data, files, name):
            upload = super().value_from_datadict(data, files, name)
            if not self.is_required and CheckboxInput().value_from_datadict(
                    data, files, self.clear_checkbox_name(name)):

                if upload:
                    # If the user contradicts themselves (uploads a new file AND
                    # checks the "clear" checkbox), we return a unique marker
                    # object that FileField will turn into a ValidationError.
                    return FILE_INPUT_CONTRADICTION
                # False signals to clear any existing value, as opposed to just None
                return False
            return upload

        def use_required_attribute(self, initial):
            return super().use_required_attribute(initial) and not initial

        def value_omitted_from_data(self, data, files, name):
            return (
                super().value_omitted_from_data(data, files, name) and
                self.clear_checkbox_name(name) not in data
            )

    class Textarea(Widget):
        template_name = 'django/forms/widgets/textarea.html'

        def __init__(self, attrs=None):
            # Use slightly better defaults than HTML's 20x2 box
            default_attrs = {'cols': '40', 'rows': '10'}
            if attrs:
                default_attrs.update(attrs)
            super().__init__(default_attrs)

    class DateTimeBaseInput(TextInput):
        format_key = ''
        supports_microseconds = False

        def __init__(self, attrs=None, format=None):
            super().__init__(attrs)
            self.format = format or None

        def format_value(self, value):
            return formats.localize_input(value, self.format or formats.get_format(self.format_key)[0])

    class DateInput(DateTimeBaseInput):
        format_key = 'DATE_INPUT_FORMATS'
        template_name = 'django/forms/widgets/date.html'

    class DateTimeInput(DateTimeBaseInput):
        format_key = 'DATETIME_INPUT_FORMATS'
        template_name = 'django/forms/widgets/datetime.html'

    class TimeInput(DateTimeBaseInput):
        format_key = 'TIME_INPUT_FORMATS'
        template_name = 'django/forms/widgets/time.html'

    # Defined at module level so that CheckboxInput is picklable (#17976)
    def boolean_check(v):
        return not (v is False or v is None or v == '')

    class CheckboxInput(Input):
        input_type = 'checkbox'
        template_name = 'django/forms/widgets/checkbox.html'

        def __init__(self, attrs=None, check_test=None):
            super().__init__(attrs)
            # check_test is a callable that takes a value and returns True
            # if the checkbox should be checked for that value.
            self.check_test = boolean_check if check_test is None else check_test

        def format_value(self, value):
            """Only return the 'value' attribute if value isn't empty."""
            if value is True or value is False or value is None or value == '':
                return
            return str(value)

        def get_context(self, name, value, attrs):
            if self.check_test(value):
                if attrs is None:
                    attrs = {}
                attrs['checked'] = True
            return super().get_context(name, value, attrs)

        def value_from_datadict(self, data, files, name):
            if name not in data:
                # A missing value means False because HTML form submission does not
                # send results for unselected checkboxes.
                return False
            value = data.get(name)
            # Translate true and false strings to boolean values.
            values = {'true': True, 'false': False}
            if isinstance(value, str):
                value = values.get(value.lower(), value)
            return bool(value)

        def value_omitted_from_data(self, data, files, name):
            # HTML checkboxes don't appear in POST data if not checked, so it's
            # never known if the value is actually omitted.
            return False

    class ChoiceWidget(Widget):
        allow_multiple_selected = False
        input_type = None
        template_name = None
        option_template_name = None
        add_id_index = True
        checked_attribute = {'checked': True}
        option_inherits_attrs = True

        def __init__(self, attrs=None, choices=()):
            super().__init__(attrs)
            # choices can be any iterable, but we may need to render this widget
            # multiple times. Thus, collapse it into a list so it can be consumed
            # more than once.
            self.choices = list(choices)

        def __deepcopy__(self, memo):
            obj = copy.copy(self)
            obj.attrs = self.attrs.copy()
            obj.choices = copy.copy(self.choices)
            memo[id(self)] = obj
            return obj

        def subwidgets(self, name, value, attrs=None):
            """
            Yield all "subwidgets" of this widget. Used to enable iterating
            options from a BoundField for choice widgets.
            """
            value = self.format_value(value)
            yield from self.options(name, value, attrs)

        def options(self, name, value, attrs=None):
            """Yield a flat list of options for this widgets."""
            for group in self.optgroups(name, value, attrs):
                yield from group[1]

        def optgroups(self, name, value, attrs=None):
            """Return a list of optgroups for this widget."""
            groups = []
            has_selected = False

            for index, (option_value, option_label) in enumerate(self.choices):
                if option_value is None:
                    option_value = ''

                subgroup = []
                if isinstance(option_label, (list, tuple)):
                    group_name = option_value
                    subindex = 0
                    choices = option_label
                else:
                    group_name = None
                    subindex = None
                    choices = [(option_value, option_label)]
                groups.append((group_name, subgroup, index))

                for subvalue, sublabel in choices:
                    selected = (
                        str(subvalue) in value and
                        (not has_selected or self.allow_multiple_selected)
                    )
                    has_selected |= selected
                    subgroup.append(self.create_option(
                        name, subvalue, sublabel, selected, index,
                        subindex=subindex, attrs=attrs,
                    ))
                    if subindex is not None:
                        subindex += 1
            return groups

        def create_option(self, name, value, label, selected, index, subindex=None, attrs=None):
            index = str(index) if subindex is None else "%s_%s" % (index, subindex)
            if attrs is None:
                attrs = {}
            option_attrs = self.build_attrs(self.attrs, attrs) if self.option_inherits_attrs else {}
            if selected:
                option_attrs.update(self.checked_attribute)
            if 'id' in option_attrs:
                option_attrs['id'] = self.id_for_label(option_attrs['id'], index)
            return {
                'name': name,
                'value': value,
                'label': label,
                'selected': selected,
                'index': index,
                'attrs': option_attrs,
                'type': self.input_type,
                'template_name': self.option_template_name,
                'wrap_label': True,
            }

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            context['widget']['optgroups'] = self.optgroups(name, context['widget']['value'], attrs)
            return context

        def id_for_label(self, id_, index='0'):
            """
            Use an incremented id for each option where the main widget
            references the zero index.
            """
            if id_ and self.add_id_index:
                id_ = '%s_%s' % (id_, index)
            return id_

        def value_from_datadict(self, data, files, name):
            getter = data.get
            if self.allow_multiple_selected:
                try:
                    getter = data.getlist
                except AttributeError:
                    pass
            return getter(name)

        def format_value(self, value):
            """Return selected values as a list."""
            if value is None and self.allow_multiple_selected:
                return []
            if not isinstance(value, (tuple, list)):
                value = [value]
            return [str(v) if v is not None else '' for v in value]

    class Select(ChoiceWidget):
        input_type = 'select'
        template_name = 'django/forms/widgets/select.html'
        option_template_name = 'django/forms/widgets/select_option.html'
        add_id_index = False
        checked_attribute = {'selected': True}
        option_inherits_attrs = False

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            if self.allow_multiple_selected:
                context['widget']['attrs']['multiple'] = True
            return context

        @staticmethod
        def _choice_has_empty_value(choice):
            """Return True if the choice's value is empty string or None."""
            value, _ = choice
            return value is None or value == ''

        def use_required_attribute(self, initial):
            """
            Don't render 'required' if the first <option> has a value, as that's
            invalid HTML.
            """
            use_required_attribute = super().use_required_attribute(initial)
            # 'required' is always okay for <select multiple>.
            if self.allow_multiple_selected:
                return use_required_attribute

            first_choice = next(iter(self.choices), None)
            return use_required_attribute and first_choice is not None and self._choice_has_empty_value(first_choice)

    class NullBooleanSelect(Select):
        """
        A Select Widget intended to be used with NullBooleanField.
        """
        def __init__(self, attrs=None):
            choices = (
                ('1', _('Unknown')),
                ('2', _('Yes')),
                ('3', _('No')),
            )
            super().__init__(attrs, choices)

        def format_value(self, value):
            try:
                return {True: '2', False: '3', '2': '2', '3': '3'}[value]
            except KeyError:
                return '1'

        def value_from_datadict(self, data, files, name):
            value = data.get(name)
            return {
                '2': True,
                True: True,
                'True': True,
                '3': False,
                'False': False,
                False: False,
            }.get(value)

    class SelectMultiple(Select):
        allow_multiple_selected = True

        def value_from_datadict(self, data, files, name):
            try:
                getter = data.getlist
            except AttributeError:
                getter = data.get
            return getter(name)

        def value_omitted_from_data(self, data, files, name):
            # An unselected <select multiple> doesn't appear in POST data, so it's
            # never known if the value is actually omitted.
            return False

    class RadioSelect(ChoiceWidget):
        input_type = 'radio'
        template_name = 'django/forms/widgets/radio.html'
        option_template_name = 'django/forms/widgets/radio_option.html'

    class CheckboxSelectMultiple(ChoiceWidget):
        allow_multiple_selected = True
        input_type = 'checkbox'
        template_name = 'django/forms/widgets/checkbox_select.html'
        option_template_name = 'django/forms/widgets/checkbox_option.html'

        def use_required_attribute(self, initial):
            # Don't use the 'required' attribute because browser validation would
            # require all checkboxes to be checked instead of at least one.
            return False

        def value_omitted_from_data(self, data, files, name):
            # HTML checkboxes don't appear in POST data if not checked, so it's
            # never known if the value is actually omitted.
            return False

        def id_for_label(self, id_, index=None):
            """"
            Don't include for="field_0" in <label> because clicking such a label
            would toggle the first checkbox.
            """
            if index is None:
                return ''
            return super().id_for_label(id_, index)

    class MultiWidget(Widget):
        """
        A widget that is composed of multiple widgets.

        In addition to the values added by Widget.get_context(), this widget
        adds a list of subwidgets to the context as widget['subwidgets'].
        These can be looped over and rendered like normal widgets.

        You'll probably want to use this class with MultiValueField.
        """
        template_name = 'django/forms/widgets/multiwidget.html'

        def __init__(self, widgets, attrs=None):
            self.widgets = [w() if isinstance(w, type) else w for w in widgets]
            super().__init__(attrs)

        @property
        def is_hidden(self):
            return all(w.is_hidden for w in self.widgets)

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            if self.is_localized:
                for widget in self.widgets:
                    widget.is_localized = self.is_localized
            # value is a list of values, each corresponding to a widget
            # in self.widgets.
            if not isinstance(value, list):
                value = self.decompress(value)

            final_attrs = context['widget']['attrs']
            input_type = final_attrs.pop('type', None)
            id_ = final_attrs.get('id')
            subwidgets = []
            for i, widget in enumerate(self.widgets):
                if input_type is not None:
                    widget.input_type = input_type
                widget_name = '%s_%s' % (name, i)
                try:
                    widget_value = value[i]
                except IndexError:
                    widget_value = None
                if id_:
                    widget_attrs = final_attrs.copy()
                    widget_attrs['id'] = '%s_%s' % (id_, i)
                else:
                    widget_attrs = final_attrs
                subwidgets.append(widget.get_context(widget_name, widget_value, widget_attrs)['widget'])
            context['widget']['subwidgets'] = subwidgets
            return context

        def id_for_label(self, id_):
            if id_:
                id_ += '_0'
            return id_

        def value_from_datadict(self, data, files, name):
            return [widget.value_from_datadict(data, files, name + '_%s' % i) for i, widget in enumerate(self.widgets)]

        def value_omitted_from_data(self, data, files, name):
            return all(
                widget.value_omitted_from_data(data, files, name + '_%s' % i)
                for i, widget in enumerate(self.widgets)
            )

        def decompress(self, value):
            """
            Return a list of decompressed values for the given compressed value.
            The given value can be assumed to be valid, but not necessarily
            non-empty.
            """
            raise NotImplementedError('Subclasses must implement this method.')

        def _get_media(self):
            """
            Media for a multiwidget is the combination of all media of the
            subwidgets.
            """
            media = Media()
            for w in self.widgets:
                media = media + w.media
            return media
        media = property(_get_media)

        def __deepcopy__(self, memo):
            obj = super().__deepcopy__(memo)
            obj.widgets = copy.deepcopy(self.widgets)
            return obj

        @property
        def needs_multipart_form(self):
            return any(w.needs_multipart_form for w in self.widgets)

    class SplitDateTimeWidget(MultiWidget):
        """
        A widget that splits datetime input into two <input type="text"> boxes.
        """
        supports_microseconds = False
        template_name = 'django/forms/widgets/splitdatetime.html'

        def __init__(self, attrs=None, date_format=None, time_format=None, date_attrs=None, time_attrs=None):
            widgets = (
                DateInput(
                    attrs=attrs if date_attrs is None else date_attrs,
                    format=date_format,
                ),
                TimeInput(
                    attrs=attrs if time_attrs is None else time_attrs,
                    format=time_format,
                ),
            )
            super().__init__(widgets)

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

    class SplitHiddenDateTimeWidget(SplitDateTimeWidget):
        """
        A widget that splits datetime input into two <input type="hidden"> inputs.
        """
        template_name = 'django/forms/widgets/splithiddendatetime.html'

        def __init__(self, attrs=None, date_format=None, time_format=None, date_attrs=None, time_attrs=None):
            super().__init__(attrs, date_format, time_format, date_attrs, time_attrs)
            for widget in self.widgets:
                widget.input_type = 'hidden'

    class SelectDateWidget(Widget):
        """
        A widget that splits date input into three <select> boxes.

        This also serves as an example of a Widget that has more than one HTML
        element and hence implements value_from_datadict.
        """
        none_value = ('', '---')
        month_field = '%s_month'
        day_field = '%s_day'
        year_field = '%s_year'
        template_name = 'django/forms/widgets/select_date.html'
        input_type = 'select'
        select_widget = Select
        date_re = re.compile(r'(\d{4}|0)-(\d\d?)-(\d\d?)$')

        def __init__(self, attrs=None, years=None, months=None, empty_label=None):
            self.attrs = attrs or {}

            # Optional list or tuple of years to use in the "year" select box.
            if years:
                self.years = years
            else:
                this_year = datetime.date.today().year
                self.years = range(this_year, this_year + 10)

            # Optional dict of months to use in the "month" select box.
            if months:
                self.months = months
            else:
                self.months = MONTHS

            # Optional string, list, or tuple to use as empty_label.
            if isinstance(empty_label, (list, tuple)):
                if not len(empty_label) == 3:
                    raise ValueError('empty_label list/tuple must have 3 elements.')

                self.year_none_value = ('', empty_label[0])
                self.month_none_value = ('', empty_label[1])
                self.day_none_value = ('', empty_label[2])
            else:
                if empty_label is not None:
                    self.none_value = ('', empty_label)

                self.year_none_value = self.none_value
                self.month_none_value = self.none_value
                self.day_none_value = self.none_value

        def get_context(self, name, value, attrs):
            context = super().get_context(name, value, attrs)
            date_context = {}
            year_choices = [(i, str(i)) for i in self.years]
            if not self.is_required:
                year_choices.insert(0, self.year_none_value)
            year_name = self.year_field % name
            date_context['year'] = self.select_widget(attrs, choices=year_choices).get_context(
                name=year_name,
                value=context['widget']['value']['year'],
                attrs={**context['widget']['attrs'], 'id': 'id_%s' % year_name},
            )
            month_choices = list(self.months.items())
            if not self.is_required:
                month_choices.insert(0, self.month_none_value)
            month_name = self.month_field % name
            date_context['month'] = self.select_widget(attrs, choices=month_choices).get_context(
                name=month_name,
                value=context['widget']['value']['month'],
                attrs={**context['widget']['attrs'], 'id': 'id_%s' % month_name},
            )
            day_choices = [(i, i) for i in range(1, 32)]
            if not self.is_required:
                day_choices.insert(0, self.day_none_value)
            day_name = self.day_field % name
            date_context['day'] = self.select_widget(attrs, choices=day_choices,).get_context(
                name=day_name,
                value=context['widget']['value']['day'],
                attrs={**context['widget']['attrs'], 'id': 'id_%s' % day_name},
            )
            subwidgets = []
            for field in self._parse_date_fmt():
                subwidgets.append(date_context[field]['widget'])
            context['widget']['subwidgets'] = subwidgets
            return context

        def format_value(self, value):
            """
            Return a dict containing the year, month, and day of the current value.
            Use dict instead of a datetime to allow invalid dates such as February
            31 to display correctly.
            """
            year, month, day = None, None, None
            if isinstance(value, (datetime.date, datetime.datetime)):
                year, month, day = value.year, value.month, value.day
            elif isinstance(value, str):
                match = self.date_re.match(value)
                if match:
                    # Convert any zeros in the date to empty strings to match the
                    # empty option value.
                    year, month, day = [int(val) or '' for val in match.groups()]
                elif settings.USE_L10N:
                    input_format = get_format('DATE_INPUT_FORMATS')[0]
                    try:
                        d = datetime.datetime.strptime(value, input_format)
                    except ValueError:
                        pass
                    else:
                        year, month, day = d.year, d.month, d.day
            return {'year': year, 'month': month, 'day': day}

        @staticmethod
        def _parse_date_fmt():
            fmt = get_format('DATE_FORMAT')
            escaped = False
            for char in fmt:
                if escaped:
                    escaped = False
                elif char == '\\':
                    escaped = True
                elif char in 'Yy':
                    yield 'year'
                elif char in 'bEFMmNn':
                    yield 'month'
                elif char in 'dj':
                    yield 'day'

        def id_for_label(self, id_):
            for first_select in self._parse_date_fmt():
                return '%s_%s' % (id_, first_select)
            return '%s_month' % id_

        def value_from_datadict(self, data, files, name):
            y = data.get(self.year_field % name)
            m = data.get(self.month_field % name)
            d = data.get(self.day_field % name)
            if y == m == d == '':
                return None
            if y is not None and m is not None and d is not None:
                if settings.USE_L10N:
                    input_format = get_format('DATE_INPUT_FORMATS')[0]
                    try:
                        date_value = datetime.date(int(y), int(m), int(d))
                    except ValueError:
                        pass
                    else:
                        date_value = datetime_safe.new_date(date_value)
                        return date_value.strftime(input_format)
                # Return pseudo-ISO dates with zeros for any unselected values,
                # e.g. '2017-0-23'.
                return '%s-%s-%s' % (y or 0, m or 0, d or 0)
            return data.get(name)

        def value_omitted_from_data(self, data, files, name):
            return not any(
                ('{}_{}'.format(name, interval) in data)
                for interval in ('year', 'month', 'day')
            )