text: """
  Field classes.
  """
  
  from __future__ import unicode_literals
  
  import copy
  import datetime
  import os
  import re
  import sys
  import uuid
  import warnings
  from decimal import Decimal, DecimalException
  from io import BytesIO
  
  from django.core import validators
  from django.core.exceptions import ValidationError
  # Provide this import for backwards compatibility.
  from django.core.validators import EMPTY_VALUES  # NOQA
  from django.forms.boundfield import BoundField
  from django.forms.utils import from_current_timezone, to_current_timezone
  from django.forms.widgets import (
      FILE_INPUT_CONTRADICTION, CheckboxInput, ClearableFileInput, DateInput,
      DateTimeInput, EmailInput, HiddenInput, MultipleHiddenInput,
      NullBooleanSelect, NumberInput, Select, SelectMultiple,
      SplitDateTimeWidget, SplitHiddenDateTimeWidget, TextInput, TimeInput,
      URLInput,
  )
  from django.utils import formats, six
  from django.utils.dateparse import parse_duration
  from django.utils.deprecation import (
      RemovedInDjango110Warning, RenameMethodsBase,
  )
  from django.utils.duration import duration_string
  from django.utils.encoding import force_str, force_text, smart_text
  from django.utils.ipv6 import clean_ipv6_address
  from django.utils.six.moves.urllib.parse import urlsplit, urlunsplit
  from django.utils.translation import ugettext_lazy as _, ungettext_lazy
  
  __all__ = (
      'Field', 'CharField', 'IntegerField',
      'DateField', 'TimeField', 'DateTimeField', 'DurationField',
      'RegexField', 'EmailField', 'FileField', 'ImageField', 'URLField',
      'BooleanField', 'NullBooleanField', 'ChoiceField', 'MultipleChoiceField',
      'ComboField', 'MultiValueField', 'FloatField', 'DecimalField',
      'SplitDateTimeField', 'GenericIPAddressField', 'FilePathField',
      'SlugField', 'TypedChoiceField', 'TypedMultipleChoiceField', 'UUIDField',
  )
  
  
  class RenameFieldMethods(RenameMethodsBase):
      renamed_methods = (
          ('_has_changed', 'has_changed', RemovedInDjango110Warning),
      )
  
  
  class Field(six.with_metaclass(RenameFieldMethods, object)):
      widget = TextInput  # Default widget to use when rendering this type of Field.
      hidden_widget = HiddenInput  # Default widget to use when rendering this as "hidden".
      default_validators = []  # Default set of validators
      # Add an 'invalid' entry to default_error_message if you want a specific
      # field error message not raised by the field validators.
      default_error_messages = {
          'required': _('This field is required.'),
      }
      empty_values = list(validators.EMPTY_VALUES)
  
      # Tracks each time a Field instance is created. Used to retain order.
      creation_counter = 0
  
      def __init__(self, required=True, widget=None, label=None, initial=None,
                   help_text='', error_messages=None, show_hidden_initial=False,
                   validators=[], localize=False, disabled=False, label_suffix=None):
          # required -- Boolean that specifies whether the field is required.
          #             True by default.
          # widget -- A Widget class, or instance of a Widget class, that should
          #           be used for this Field when displaying it. Each Field has a
          #           default Widget that it'll use if you don't specify this. In
          #           most cases, the default widget is TextInput.
          # label -- A verbose name for this field, for use in displaying this
          #          field in a form. By default, Django will use a "pretty"
          #          version of the form field name, if the Field is part of a
          #          Form.
          # initial -- A value to use in this Field's initial display. This value
          #            is *not* used as a fallback if data isn't given.
          # help_text -- An optional string to use as "help text" for this Field.
          # error_messages -- An optional dictionary to override the default
          #                   messages that the field will raise.
          # show_hidden_initial -- Boolean that specifies if it is needed to render a
          #                        hidden widget with initial value after widget.
          # validators -- List of additional validators to use
          # localize -- Boolean that specifies if the field should be localized.
          # disabled -- Boolean that specifies whether the field is disabled, that
          #             is its widget is shown in the form but not editable.
          # label_suffix -- Suffix to be added to the label. Overrides
          #                 form's label_suffix.
          self.required, self.label, self.initial = required, label, initial
          self.show_hidden_initial = show_hidden_initial
          self.help_text = help_text
          self.disabled = disabled
          self.label_suffix = label_suffix
          widget = widget or self.widget
          if isinstance(widget, type):
              widget = widget()
  
          # Trigger the localization machinery if needed.
          self.localize = localize
          if self.localize:
              widget.is_localized = True
  
          # Let the widget know whether it should display as required.
          widget.is_required = self.required
  
          # Hook into self.widget_attrs() for any Field-specific HTML attributes.
          extra_attrs = self.widget_attrs(widget)
          if extra_attrs:
              widget.attrs.update(extra_attrs)
  
          self.widget = widget
  
          # Increase the creation counter, and save our local copy.
          self.creation_counter = Field.creation_counter
          Field.creation_counter += 1
  
          messages = {}
          for c in reversed(self.__class__.__mro__):
              messages.update(getattr(c, 'default_error_messages', {}))
          messages.update(error_messages or {})
          self.error_messages = messages
  
          self.validators = self.default_validators + validators
          super(Field, self).__init__()
  
      def prepare_value(self, value):
          return value
  
      def to_python(self, value):
          return value
  
      def validate(self, value):
          if value in self.empty_values and self.required:
              raise ValidationError(self.error_messages['required'], code='required')
  
      def run_validators(self, value):
          if value in self.empty_values:
              return
          errors = []
          for v in self.validators:
              try:
                  v(value)
              except ValidationError as e:
                  if hasattr(e, 'code') and e.code in self.error_messages:
                      e.message = self.error_messages[e.code]
                  errors.extend(e.error_list)
          if errors:
              raise ValidationError(errors)
  
      def clean(self, value):
          """
          Validates the given value and returns its "cleaned" value as an
          appropriate Python object.
  
          Raises ValidationError for any errors.
          """
          value = self.to_python(value)
          self.validate(value)
          self.run_validators(value)
          return value
  
      def bound_data(self, data, initial):
          """
          Return the value that should be shown for this field on render of a
          bound form, given the submitted POST data for the field and the initial
          data, if any.
  
          For most fields, this will simply be data; FileFields need to handle it
          a bit differently.
          """
          return data
  
      def widget_attrs(self, widget):
          """
          Given a Widget instance (*not* a Widget class), returns a dictionary of
          any HTML attributes that should be added to the Widget, based on this
          Field.
          """
          return {}
  
      def has_changed(self, initial, data):
          """
          Return True if data differs from initial.
          """
          try:
              data = self.to_python(data)
              if hasattr(self, '_coerce'):
                  return self._coerce(data) != self._coerce(initial)
          except ValidationError:
              return True
          # For purposes of seeing whether something has changed, None is
          # the same as an empty string, if the data or initial value we get
          # is None, replace it with ''.
          initial_value = initial if initial is not None else ''
          data_value = data if data is not None else ''
          return initial_value != data_value
  
      def get_bound_field(self, form, field_name):
          """
          Return a BoundField instance that will be used when accessing the form
          field in a template.
          """
          return BoundField(form, self, field_name)
  
      def __deepcopy__(self, memo):
          result = copy.copy(self)
          memo[id(self)] = result
          result.widget = copy.deepcopy(self.widget, memo)
          result.validators = self.validators[:]
          return result
  
  
  class CharField(Field):
      def __init__(self, max_length=None, min_length=None, strip=True, *args, **kwargs):
          self.max_length = max_length
          self.min_length = min_length
          self.strip = strip
          super(CharField, self).__init__(*args, **kwargs)
          if min_length is not None:
              self.validators.append(validators.MinLengthValidator(int(min_length)))
          if max_length is not None:
              self.validators.append(validators.MaxLengthValidator(int(max_length)))
  
      def to_python(self, value):
          "Returns a Unicode object."
          if value in self.empty_values:
              return ''
          value = force_text(value)
          if self.strip:
              value = value.strip()
          return value
  
      def widget_attrs(self, widget):
          attrs = super(CharField, self).widget_attrs(widget)
          if self.max_length is not None:
              # The HTML attribute is maxlength, not max_length.
              attrs.update({'maxlength': str(self.max_length)})
          return attrs
  
  
  class IntegerField(Field):
      widget = NumberInput
      default_error_messages = {
          'invalid': _('Enter a whole number.'),
      }
      re_decimal = re.compile(r'\.0*\s*$')
  
      def __init__(self, max_value=None, min_value=None, *args, **kwargs):
          self.max_value, self.min_value = max_value, min_value
          if kwargs.get('localize') and self.widget == NumberInput:
              # Localized number input is not well supported on most browsers
              kwargs.setdefault('widget', super(IntegerField, self).widget)
          super(IntegerField, self).__init__(*args, **kwargs)
  
          if max_value is not None:
              self.validators.append(validators.MaxValueValidator(max_value))
          if min_value is not None:
              self.validators.append(validators.MinValueValidator(min_value))
  
      def to_python(self, value):
          """
          Validates that int() can be called on the input. Returns the result
          of int(). Returns None for empty values.
          """
          value = super(IntegerField, self).to_python(value)
          if value in self.empty_values:
              return None
          if self.localize:
              value = formats.sanitize_separators(value)
          # Strip trailing decimal and zeros.
          try:
              value = int(self.re_decimal.sub('', str(value)))
          except (ValueError, TypeError):
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          return value
  
      def widget_attrs(self, widget):
          attrs = super(IntegerField, self).widget_attrs(widget)
          if isinstance(widget, NumberInput):
              if self.min_value is not None:
                  attrs['min'] = self.min_value
              if self.max_value is not None:
                  attrs['max'] = self.max_value
          return attrs
  
  
  class FloatField(IntegerField):
      default_error_messages = {
          'invalid': _('Enter a number.'),
      }
  
      def to_python(self, value):
          """
          Validates that float() can be called on the input. Returns the result
          of float(). Returns None for empty values.
          """
          value = super(IntegerField, self).to_python(value)
          if value in self.empty_values:
              return None
          if self.localize:
              value = formats.sanitize_separators(value)
          try:
              value = float(value)
          except (ValueError, TypeError):
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          return value
  
      def validate(self, value):
          super(FloatField, self).validate(value)
  
          # Check for NaN (which is the only thing not equal to itself) and +/- infinity
          if value != value or value in (Decimal('Inf'), Decimal('-Inf')):
              raise ValidationError(self.error_messages['invalid'], code='invalid')
  
          return value
  
      def widget_attrs(self, widget):
          attrs = super(FloatField, self).widget_attrs(widget)
          if isinstance(widget, NumberInput) and 'step' not in widget.attrs:
              attrs.setdefault('step', 'any')
          return attrs
  
  
  class DecimalField(IntegerField):
      default_error_messages = {
          'invalid': _('Enter a number.'),
      }
  
      def __init__(self, max_value=None, min_value=None, max_digits=None, decimal_places=None, *args, **kwargs):
          self.max_digits, self.decimal_places = max_digits, decimal_places
          super(DecimalField, self).__init__(max_value, min_value, *args, **kwargs)
          self.validators.append(validators.DecimalValidator(max_digits, decimal_places))
  
      def to_python(self, value):
          """
          Validates that the input is a decimal number. Returns a Decimal
          instance. Returns None for empty values. Ensures that there are no more
          than max_digits in the number, and no more than decimal_places digits
          after the decimal point.
          """
          if value in self.empty_values:
              return None
          if self.localize:
              value = formats.sanitize_separators(value)
          value = smart_text(value).strip()
          try:
              value = Decimal(value)
          except DecimalException:
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          return value
  
      def validate(self, value):
          super(DecimalField, self).validate(value)
          if value in self.empty_values:
              return
          # Check for NaN, Inf and -Inf values. We can't compare directly for NaN,
          # since it is never equal to itself. However, NaN is the only value that
          # isn't equal to itself, so we can use this to identify NaN
          if value != value or value == Decimal("Inf") or value == Decimal("-Inf"):
              raise ValidationError(self.error_messages['invalid'], code='invalid')
  
      def widget_attrs(self, widget):
          attrs = super(DecimalField, self).widget_attrs(widget)
          if isinstance(widget, NumberInput) and 'step' not in widget.attrs:
              if self.decimal_places is not None:
                  # Use exponential notation for small values since they might
                  # be parsed as 0 otherwise. ref #20765
                  step = str(Decimal('1') / 10 ** self.decimal_places).lower()
              else:
                  step = 'any'
              attrs.setdefault('step', step)
          return attrs
  
  
  class BaseTemporalField(Field):
  
      def __init__(self, input_formats=None, *args, **kwargs):
          super(BaseTemporalField, self).__init__(*args, **kwargs)
          if input_formats is not None:
              self.input_formats = input_formats
  
      def to_python(self, value):
          # Try to coerce the value to unicode.
          unicode_value = force_text(value, strings_only=True)
          if isinstance(unicode_value, six.text_type):
              value = unicode_value.strip()
          # If unicode, try to strptime against each input format.
          if isinstance(value, six.text_type):
              for format in self.input_formats:
                  try:
                      return self.strptime(value, format)
                  except (ValueError, TypeError):
                      continue
          raise ValidationError(self.error_messages['invalid'], code='invalid')
  
      def strptime(self, value, format):
          raise NotImplementedError('Subclasses must define this method.')
  
  
  class DateField(BaseTemporalField):
      widget = DateInput
      input_formats = formats.get_format_lazy('DATE_INPUT_FORMATS')
      default_error_messages = {
          'invalid': _('Enter a valid date.'),
      }
  
      def to_python(self, value):
          """
          Validates that the input can be converted to a date. Returns a Python
          datetime.date object.
          """
          if value in self.empty_values:
              return None
          if isinstance(value, datetime.datetime):
              return value.date()
          if isinstance(value, datetime.date):
              return value
          return super(DateField, self).to_python(value)
  
      def strptime(self, value, format):
          return datetime.datetime.strptime(force_str(value), format).date()
  
  
  class TimeField(BaseTemporalField):
      widget = TimeInput
      input_formats = formats.get_format_lazy('TIME_INPUT_FORMATS')
      default_error_messages = {
          'invalid': _('Enter a valid time.')
      }
  
      def to_python(self, value):
          """
          Validates that the input can be converted to a time. Returns a Python
          datetime.time object.
          """
          if value in self.empty_values:
              return None
          if isinstance(value, datetime.time):
              return value
          return super(TimeField, self).to_python(value)
  
      def strptime(self, value, format):
          return datetime.datetime.strptime(force_str(value), format).time()
  
  
  class DateTimeField(BaseTemporalField):
      widget = DateTimeInput
      input_formats = formats.get_format_lazy('DATETIME_INPUT_FORMATS')
      default_error_messages = {
          'invalid': _('Enter a valid date/time.'),
      }
  
      def prepare_value(self, value):
          if isinstance(value, datetime.datetime):
              value = to_current_timezone(value)
          return value
  
      def to_python(self, value):
          """
          Validates that the input can be converted to a datetime. Returns a
          Python datetime.datetime object.
          """
          if value in self.empty_values:
              return None
          if isinstance(value, datetime.datetime):
              return from_current_timezone(value)
          if isinstance(value, datetime.date):
              result = datetime.datetime(value.year, value.month, value.day)
              return from_current_timezone(result)
          result = super(DateTimeField, self).to_python(value)
          return from_current_timezone(result)
  
      def strptime(self, value, format):
          return datetime.datetime.strptime(force_str(value), format)
  
  
  class DurationField(Field):
      default_error_messages = {
          'invalid': _('Enter a valid duration.'),
      }
  
      def prepare_value(self, value):
          if isinstance(value, datetime.timedelta):
              return duration_string(value)
          return value
  
      def to_python(self, value):
          if value in self.empty_values:
              return None
          if isinstance(value, datetime.timedelta):
              return value
          value = parse_duration(value)
          if value is None:
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          return value
  
  
  class RegexField(CharField):
      def __init__(self, regex, max_length=None, min_length=None, error_message=None, *args, **kwargs):
          """
          regex can be either a string or a compiled regular expression object.
          error_message is an optional error message to use, if
          'Enter a valid value' is too generic for you.
          """
          kwargs.setdefault('strip', False)
          # error_message is just kept for backwards compatibility:
          if error_message is not None:
              warnings.warn(
                  "The 'error_message' argument is deprecated. Use "
                  "Field.error_messages['invalid'] instead.",
                  RemovedInDjango110Warning, stacklevel=2
              )
              error_messages = kwargs.get('error_messages') or {}
              error_messages['invalid'] = error_message
              kwargs['error_messages'] = error_messages
          super(RegexField, self).__init__(max_length, min_length, *args, **kwargs)
          self._set_regex(regex)
  
      def _get_regex(self):
          return self._regex
  
      def _set_regex(self, regex):
          if isinstance(regex, six.string_types):
              regex = re.compile(regex, re.UNICODE)
          self._regex = regex
          if hasattr(self, '_regex_validator') and self._regex_validator in self.validators:
              self.validators.remove(self._regex_validator)
          self._regex_validator = validators.RegexValidator(regex=regex)
          self.validators.append(self._regex_validator)
  
      regex = property(_get_regex, _set_regex)
  
  
  class EmailField(CharField):
      widget = EmailInput
      default_validators = [validators.validate_email]
  
      def clean(self, value):
          value = self.to_python(value).strip()
          return super(EmailField, self).clean(value)
  
  
  class FileField(Field):
      widget = ClearableFileInput
      default_error_messages = {
          'invalid': _("No file was submitted. Check the encoding type on the form."),
          'missing': _("No file was submitted."),
          'empty': _("The submitted file is empty."),
          'max_length': ungettext_lazy(
              'Ensure this filename has at most %(max)d character (it has %(length)d).',
              'Ensure this filename has at most %(max)d characters (it has %(length)d).',
              'max'),
          'contradiction': _('Please either submit a file or check the clear checkbox, not both.')
      }
  
      def __init__(self, *args, **kwargs):
          self.max_length = kwargs.pop('max_length', None)
          self.allow_empty_file = kwargs.pop('allow_empty_file', False)
          super(FileField, self).__init__(*args, **kwargs)
  
      def to_python(self, data):
          if data in self.empty_values:
              return None
  
          # UploadedFile objects should have name and size attributes.
          try:
              file_name = data.name
              file_size = data.size
          except AttributeError:
              raise ValidationError(self.error_messages['invalid'], code='invalid')
  
          if self.max_length is not None and len(file_name) > self.max_length:
              params = {'max': self.max_length, 'length': len(file_name)}
              raise ValidationError(self.error_messages['max_length'], code='max_length', params=params)
          if not file_name:
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          if not self.allow_empty_file and not file_size:
              raise ValidationError(self.error_messages['empty'], code='empty')
  
          return data
  
      def clean(self, data, initial=None):
          # If the widget got contradictory inputs, we raise a validation error
          if data is FILE_INPUT_CONTRADICTION:
              raise ValidationError(self.error_messages['contradiction'], code='contradiction')
          # False means the field value should be cleared; further validation is
          # not needed.
          if data is False:
              if not self.required:
                  return False
              # If the field is required, clearing is not possible (the widget
              # shouldn't return False data in that case anyway). False is not
              # in self.empty_value; if a False value makes it this far
              # it should be validated from here on out as None (so it will be
              # caught by the required check).
              data = None
          if not data and initial:
              return initial
          return super(FileField, self).clean(data)
  
      def bound_data(self, data, initial):
          if data in (None, FILE_INPUT_CONTRADICTION):
              return initial
          return data
  
      def has_changed(self, initial, data):
          if data is None:
              return False
          return True
  
  
  class ImageField(FileField):
      default_error_messages = {
          'invalid_image': _(
              "Upload a valid image. The file you uploaded was either not an "
              "image or a corrupted image."
          ),
      }
  
      def to_python(self, data):
          """
          Checks that the file-upload field data contains a valid image (GIF, JPG,
          PNG, possibly others -- whatever the Python Imaging Library supports).
          """
          f = super(ImageField, self).to_python(data)
          if f is None:
              return None
  
          from PIL import Image
  
          # We need to get a file object for Pillow. We might have a path or we might
          # have to read the data into memory.
          if hasattr(data, 'temporary_file_path'):
              file = data.temporary_file_path()
          else:
              if hasattr(data, 'read'):
                  file = BytesIO(data.read())
              else:
                  file = BytesIO(data['content'])
  
          try:
              # load() could spot a truncated JPEG, but it loads the entire
              # image in memory, which is a DoS vector. See #3848 and #18520.
              image = Image.open(file)
              # verify() must be called immediately after the constructor.
              image.verify()
  
              # Annotating so subclasses can reuse it for their own validation
              f.image = image
              # Pillow doesn't detect the MIME type of all formats. In those
              # cases, content_type will be None.
              f.content_type = Image.MIME.get(image.format)
          except Exception:
              # Pillow doesn't recognize it as an image.
              six.reraise(ValidationError, ValidationError(
                  self.error_messages['invalid_image'],
                  code='invalid_image',
              ), sys.exc_info()[2])
          if hasattr(f, 'seek') and callable(f.seek):
              f.seek(0)
          return f
  
  
  class URLField(CharField):
      widget = URLInput
      default_error_messages = {
          'invalid': _('Enter a valid URL.'),
      }
      default_validators = [validators.URLValidator()]
  
      def to_python(self, value):
  
          def split_url(url):
              """
              Returns a list of url parts via ``urlparse.urlsplit`` (or raises a
              ``ValidationError`` exception for certain).
              """
              try:
                  return list(urlsplit(url))
              except ValueError:
                  # urlparse.urlsplit can raise a ValueError with some
                  # misformatted URLs.
                  raise ValidationError(self.error_messages['invalid'], code='invalid')
  
          value = super(URLField, self).to_python(value)
          if value:
              url_fields = split_url(value)
              if not url_fields[0]:
                  # If no URL scheme given, assume http://
                  url_fields[0] = 'http'
              if not url_fields[1]:
                  # Assume that if no domain is provided, that the path segment
                  # contains the domain.
                  url_fields[1] = url_fields[2]
                  url_fields[2] = ''
                  # Rebuild the url_fields list, since the domain segment may now
                  # contain the path too.
                  url_fields = split_url(urlunsplit(url_fields))
              value = urlunsplit(url_fields)
          return value
  
      def clean(self, value):
          value = self.to_python(value).strip()
          return super(URLField, self).clean(value)
  
  
  class BooleanField(Field):
      widget = CheckboxInput
  
      def to_python(self, value):
          """Returns a Python boolean object."""
          # Explicitly check for the string 'False', which is what a hidden field
          # will submit for False. Also check for '0', since this is what
          # RadioSelect will provide. Because bool("True") == bool('1') == True,
          # we don't need to handle that explicitly.
          if isinstance(value, six.string_types) and value.lower() in ('false', '0'):
              value = False
          else:
              value = bool(value)
          return super(BooleanField, self).to_python(value)
  
      def validate(self, value):
          if not value and self.required:
              raise ValidationError(self.error_messages['required'], code='required')
  
      def has_changed(self, initial, data):
          # Sometimes data or initial could be None or '' which should be the
          # same thing as False.
          if initial == 'False':
              # show_hidden_initial may have transformed False to 'False'
              initial = False
          return bool(initial) != bool(data)
  
  
  class NullBooleanField(BooleanField):
      """
      A field whose valid values are None, True and False. Invalid values are
      cleaned to None.
      """
      widget = NullBooleanSelect
  
      def to_python(self, value):
          """
          Explicitly checks for the string 'True' and 'False', which is what a
          hidden field will submit for True and False, for 'true' and 'false',
          which are likely to be returned by JavaScript serializations of forms,
          and for '1' and '0', which is what a RadioField will submit. Unlike
          the Booleanfield we need to explicitly check for True, because we are
          not using the bool() function
          """
          if value in (True, 'True', 'true', '1'):
              return True
          elif value in (False, 'False', 'false', '0'):
              return False
          else:
              return None
  
      def validate(self, value):
          pass
  
      def has_changed(self, initial, data):
          # None (unknown) and False (No) are not the same
          if initial is not None:
              initial = bool(initial)
          if data is not None:
              data = bool(data)
          return initial != data
  
  
  class CallableChoiceIterator(object):
      def __init__(self, choices_func):
          self.choices_func = choices_func
  
      def __iter__(self):
          for e in self.choices_func():
              yield e
  
  
  class ChoiceField(Field):
      widget = Select
      default_error_messages = {
          'invalid_choice': _('Select a valid choice. %(value)s is not one of the available choices.'),
      }
  
      def __init__(self, choices=(), required=True, widget=None, label=None,
                   initial=None, help_text='', *args, **kwargs):
          super(ChoiceField, self).__init__(required=required, widget=widget, label=label,
                                          initial=initial, help_text=help_text, *args, **kwargs)
          self.choices = choices
  
      def __deepcopy__(self, memo):
          result = super(ChoiceField, self).__deepcopy__(memo)
          result._choices = copy.deepcopy(self._choices, memo)
          return result
  
      def _get_choices(self):
          return self._choices
  
      def _set_choices(self, value):
          # Setting choices also sets the choices on the widget.
          # choices can be any iterable, but we call list() on it because
          # it will be consumed more than once.
          if callable(value):
              value = CallableChoiceIterator(value)
          else:
              value = list(value)
  
          self._choices = self.widget.choices = value
  
      choices = property(_get_choices, _set_choices)
  
      def to_python(self, value):
          "Returns a Unicode object."
          if value in self.empty_values:
              return ''
          return smart_text(value)
  
      def validate(self, value):
          """
          Validates that the input is in self.choices.
          """
          super(ChoiceField, self).validate(value)
          if value and not self.valid_value(value):
              raise ValidationError(
                  self.error_messages['invalid_choice'],
                  code='invalid_choice',
                  params={'value': value},
              )
  
      def valid_value(self, value):
          "Check to see if the provided value is a valid choice"
          text_value = force_text(value)
          for k, v in self.choices:
              if isinstance(v, (list, tuple)):
                  # This is an optgroup, so look inside the group for options
                  for k2, v2 in v:
                      if value == k2 or text_value == force_text(k2):
                          return True
              else:
                  if value == k or text_value == force_text(k):
                      return True
          return False
  
  
  class TypedChoiceField(ChoiceField):
      def __init__(self, *args, **kwargs):
          self.coerce = kwargs.pop('coerce', lambda val: val)
          self.empty_value = kwargs.pop('empty_value', '')
          super(TypedChoiceField, self).__init__(*args, **kwargs)
  
      def _coerce(self, value):
          """
          Validate that the value can be coerced to the right type (if not empty).
          """
          if value == self.empty_value or value in self.empty_values:
              return self.empty_value
          try:
              value = self.coerce(value)
          except (ValueError, TypeError, ValidationError):
              raise ValidationError(
                  self.error_messages['invalid_choice'],
                  code='invalid_choice',
                  params={'value': value},
              )
          return value
  
      def clean(self, value):
          value = super(TypedChoiceField, self).clean(value)
          return self._coerce(value)
  
  
  class MultipleChoiceField(ChoiceField):
      hidden_widget = MultipleHiddenInput
      widget = SelectMultiple
      default_error_messages = {
          'invalid_choice': _('Select a valid choice. %(value)s is not one of the available choices.'),
          'invalid_list': _('Enter a list of values.'),
      }
  
      def to_python(self, value):
          if not value:
              return []
          elif not isinstance(value, (list, tuple)):
              raise ValidationError(self.error_messages['invalid_list'], code='invalid_list')
          return [smart_text(val) for val in value]
  
      def validate(self, value):
          """
          Validates that the input is a list or tuple.
          """
          if self.required and not value:
              raise ValidationError(self.error_messages['required'], code='required')
          # Validate that each value in the value list is in self.choices.
          for val in value:
              if not self.valid_value(val):
                  raise ValidationError(
                      self.error_messages['invalid_choice'],
                      code='invalid_choice',
                      params={'value': val},
                  )
  
      def has_changed(self, initial, data):
          if initial is None:
              initial = []
          if data is None:
              data = []
          if len(initial) != len(data):
              return True
          initial_set = set(force_text(value) for value in initial)
          data_set = set(force_text(value) for value in data)
          return data_set != initial_set
  
  
  class TypedMultipleChoiceField(MultipleChoiceField):
      def __init__(self, *args, **kwargs):
          self.coerce = kwargs.pop('coerce', lambda val: val)
          self.empty_value = kwargs.pop('empty_value', [])
          super(TypedMultipleChoiceField, self).__init__(*args, **kwargs)
  
      def _coerce(self, value):
          """
          Validates that the values are in self.choices and can be coerced to the
          right type.
          """
          if value == self.empty_value or value in self.empty_values:
              return self.empty_value
          new_value = []
          for choice in value:
              try:
                  new_value.append(self.coerce(choice))
              except (ValueError, TypeError, ValidationError):
                  raise ValidationError(
                      self.error_messages['invalid_choice'],
                      code='invalid_choice',
                      params={'value': choice},
                  )
          return new_value
  
      def clean(self, value):
          value = super(TypedMultipleChoiceField, self).clean(value)
          return self._coerce(value)
  
      def validate(self, value):
          if value != self.empty_value:
              super(TypedMultipleChoiceField, self).validate(value)
          elif self.required:
              raise ValidationError(self.error_messages['required'], code='required')
  
  
  class ComboField(Field):
      """
      A Field whose clean() method calls multiple Field clean() methods.
      """
      def __init__(self, fields=(), *args, **kwargs):
          super(ComboField, self).__init__(*args, **kwargs)
          # Set 'required' to False on the individual fields, because the
          # required validation will be handled by ComboField, not by those
          # individual fields.
          for f in fields:
              f.required = False
          self.fields = fields
  
      def clean(self, value):
          """
          Validates the given value against all of self.fields, which is a
          list of Field instances.
          """
          super(ComboField, self).clean(value)
          for field in self.fields:
              value = field.clean(value)
          return value
  
  
  class MultiValueField(Field):
      """
      A Field that aggregates the logic of multiple Fields.
  
      Its clean() method takes a "decompressed" list of values, which are then
      cleaned into a single value according to self.fields. Each value in
      this list is cleaned by the corresponding field -- the first value is
      cleaned by the first field, the second value is cleaned by the second
      field, etc. Once all fields are cleaned, the list of clean values is
      "compressed" into a single value.
  
      Subclasses should not have to implement clean(). Instead, they must
      implement compress(), which takes a list of valid values and returns a
      "compressed" version of those values -- a single value.
  
      You'll probably want to use this with MultiWidget.
      """
      default_error_messages = {
          'invalid': _('Enter a list of values.'),
          'incomplete': _('Enter a complete value.'),
      }
  
      def __init__(self, fields=(), *args, **kwargs):
          self.require_all_fields = kwargs.pop('require_all_fields', True)
          super(MultiValueField, self).__init__(*args, **kwargs)
          for f in fields:
              f.error_messages.setdefault('incomplete',
                                          self.error_messages['incomplete'])
              if self.require_all_fields:
                  # Set 'required' to False on the individual fields, because the
                  # required validation will be handled by MultiValueField, not
                  # by those individual fields.
                  f.required = False
          self.fields = fields
  
      def __deepcopy__(self, memo):
          result = super(MultiValueField, self).__deepcopy__(memo)
          result.fields = tuple(x.__deepcopy__(memo) for x in self.fields)
          return result
  
      def validate(self, value):
          pass
  
      def clean(self, value):
          """
          Validates every value in the given list. A value is validated against
          the corresponding Field in self.fields.
  
          For example, if this MultiValueField was instantiated with
          fields=(DateField(), TimeField()), clean() would call
          DateField.clean(value[0]) and TimeField.clean(value[1]).
          """
          clean_data = []
          errors = []
          if not value or isinstance(value, (list, tuple)):
              if not value or not [v for v in value if v not in self.empty_values]:
                  if self.required:
                      raise ValidationError(self.error_messages['required'], code='required')
                  else:
                      return self.compress([])
          else:
              raise ValidationError(self.error_messages['invalid'], code='invalid')
          for i, field in enumerate(self.fields):
              try:
                  field_value = value[i]
              except IndexError:
                  field_value = None
              if field_value in self.empty_values:
                  if self.require_all_fields:
                      # Raise a 'required' error if the MultiValueField is
                      # required and any field is empty.
                      if self.required:
                          raise ValidationError(self.error_messages['required'], code='required')
                  elif field.required:
                      # Otherwise, add an 'incomplete' error to the list of
                      # collected errors and skip field cleaning, if a required
                      # field is empty.
                      if field.error_messages['incomplete'] not in errors:
                          errors.append(field.error_messages['incomplete'])
                      continue
              try:
                  clean_data.append(field.clean(field_value))
              except ValidationError as e:
                  # Collect all validation errors in a single list, which we'll
                  # raise at the end of clean(), rather than raising a single
                  # exception for the first error we encounter. Skip duplicates.
                  errors.extend(m for m in e.error_list if m not in errors)
          if errors:
              raise ValidationError(errors)
  
          out = self.compress(clean_data)
          self.validate(out)
          self.run_validators(out)
          return out
  
      def compress(self, data_list):
          """
          Returns a single value for the given list of values. The values can be
          assumed to be valid.
  
          For example, if this MultiValueField was instantiated with
          fields=(DateField(), TimeField()), this might return a datetime
          object created by combining the date and time in data_list.
          """
          raise NotImplementedError('Subclasses must implement this method.')
  
      def has_changed(self, initial, data):
          if initial is None:
              initial = ['' for x in range(0, len(data))]
          else:
              if not isinstance(initial, list):
                  initial = self.widget.decompress(initial)
          for field, initial, data in zip(self.fields, initial, data):
              try:
                  initial = field.to_python(initial)
              except ValidationError:
                  return True
              if field.has_changed(initial, data):
                  return True
          return False
  
  
  class FilePathField(ChoiceField):
      def __init__(self, path, match=None, recursive=False, allow_files=True,
                   allow_folders=False, required=True, widget=None, label=None,
                   initial=None, help_text='', *args, **kwargs):
          self.path, self.match, self.recursive = path, match, recursive
          self.allow_files, self.allow_folders = allow_files, allow_folders
          super(FilePathField, self).__init__(choices=(), required=required,
              widget=widget, label=label, initial=initial, help_text=help_text,
              *args, **kwargs)
  
          if self.required:
              self.choices = []
          else:
              self.choices = [("", "---------")]
  
          if self.match is not None:
              self.match_re = re.compile(self.match)
  
          if recursive:
              for root, dirs, files in sorted(os.walk(self.path)):
                  if self.allow_files:
                      for f in files:
                          if self.match is None or self.match_re.search(f):
                              f = os.path.join(root, f)
                              self.choices.append((f, f.replace(path, "", 1)))
                  if self.allow_folders:
                      for f in dirs:
                          if f == '__pycache__':
                              continue
                          if self.match is None or self.match_re.search(f):
                              f = os.path.join(root, f)
                              self.choices.append((f, f.replace(path, "", 1)))
          else:
              try:
                  for f in sorted(os.listdir(self.path)):
                      if f == '__pycache__':
                          continue
                      full_file = os.path.join(self.path, f)
                      if (((self.allow_files and os.path.isfile(full_file)) or
                              (self.allow_folders and os.path.isdir(full_file))) and
                              (self.match is None or self.match_re.search(f))):
                          self.choices.append((full_file, f))
              except OSError:
                  pass
  
          self.widget.choices = self.choices
  
  
  class SplitDateTimeField(MultiValueField):
      widget = SplitDateTimeWidget
      hidden_widget = SplitHiddenDateTimeWidget
      default_error_messages = {
          'invalid_date': _('Enter a valid date.'),
          'invalid_time': _('Enter a valid time.'),
      }
  
      def __init__(self, input_date_formats=None, input_time_formats=None, *args, **kwargs):
          errors = self.default_error_messages.copy()
          if 'error_messages' in kwargs:
              errors.update(kwargs['error_messages'])
          localize = kwargs.get('localize', False)
          fields = (
              DateField(input_formats=input_date_formats,
                        error_messages={'invalid': errors['invalid_date']},
                        localize=localize),
              TimeField(input_formats=input_time_formats,
                        error_messages={'invalid': errors['invalid_time']},
                        localize=localize),
          )
          super(SplitDateTimeField, self).__init__(fields, *args, **kwargs)
  
      def compress(self, data_list):
          if data_list:
              # Raise a validation error if time or date is empty
              # (possible if SplitDateTimeField has required=False).
              if data_list[0] in self.empty_values:
                  raise ValidationError(self.error_messages['invalid_date'], code='invalid_date')
              if data_list[1] in self.empty_values:
                  raise ValidationError(self.error_messages['invalid_time'], code='invalid_time')
              result = datetime.datetime.combine(*data_list)
              return from_current_timezone(result)
          return None
  
  
  class GenericIPAddressField(CharField):
      def __init__(self, protocol='both', unpack_ipv4=False, *args, **kwargs):
          self.unpack_ipv4 = unpack_ipv4
          self.default_validators = validators.ip_address_validators(protocol, unpack_ipv4)[0]
          super(GenericIPAddressField, self).__init__(*args, **kwargs)
  
      def to_python(self, value):
          if value in self.empty_values:
              return ''
          value = value.strip()
          if value and ':' in value:
              return clean_ipv6_address(value, self.unpack_ipv4)
          return value
  
  
  class SlugField(CharField):
      default_validators = [validators.validate_slug]
  
      def __init__(self, *args, **kwargs):
          self.allow_unicode = kwargs.pop('allow_unicode', False)
          if self.allow_unicode:
              self.default_validators = [validators.validate_unicode_slug]
          super(SlugField, self).__init__(*args, **kwargs)
  
  
  class UUIDField(CharField):
      default_error_messages = {
          'invalid': _('Enter a valid UUID.'),
      }
  
      def prepare_value(self, value):
          if isinstance(value, uuid.UUID):
              return value.hex
          return value
  
      def to_python(self, value):
          value = super(UUIDField, self).to_python(value)
          if value in self.empty_values:
              return None
          if not isinstance(value, uuid.UUID):
              try:
                  value = uuid.UUID(value)
              except ValueError:
                  raise ValidationError(self.error_messages['invalid'], code='invalid')
          return value
  