text: """
  Form classes
  """
  
  import copy
  from collections import OrderedDict
  
  from django.core.exceptions import NON_FIELD_ERRORS, ValidationError
  # BoundField is imported for backwards compatibility in Django 1.9
  from django.forms.boundfield import BoundField  # NOQA
  from django.forms.fields import Field, FileField
  # pretty_name is imported for backwards compatibility in Django 1.9
  from django.forms.utils import ErrorDict, ErrorList, pretty_name  # NOQA
  from django.forms.widgets import Media, MediaDefiningClass
  from django.utils.encoding import force_text
  from django.utils.functional import cached_property
  from django.utils.html import conditional_escape, html_safe
  from django.utils.safestring import mark_safe
  from django.utils.translation import ugettext as _
  
  from .renderers import get_default_renderer
  
  __all__ = ('BaseForm', 'Form')
  
  
  class DeclarativeFieldsMetaclass(MediaDefiningClass):
      """
      Metaclass that collects Fields declared on the base classes.
      """
      def __new__(mcs, name, bases, attrs):
          # Collect fields from current class.
          current_fields = []
          for key, value in list(attrs.items()):
              if isinstance(value, Field):
                  current_fields.append((key, value))
                  attrs.pop(key)
          attrs['declared_fields'] = OrderedDict(current_fields)
  
          new_class = super(DeclarativeFieldsMetaclass, mcs).__new__(mcs, name, bases, attrs)
  
          # Walk through the MRO.
          declared_fields = OrderedDict()
          for base in reversed(new_class.__mro__):
              # Collect fields from base class.
              if hasattr(base, 'declared_fields'):
                  declared_fields.update(base.declared_fields)
  
              # Field shadowing.
              for attr, value in base.__dict__.items():
                  if value is None and attr in declared_fields:
                      declared_fields.pop(attr)
  
          new_class.base_fields = declared_fields
          new_class.declared_fields = declared_fields
  
          return new_class
  
      @classmethod
      def __prepare__(metacls, name, bases, **kwds):
          # Remember the order in which form fields are defined.
          return OrderedDict()
  
  
  @html_safe
  class BaseForm:
      # This is the main implementation of all the Form logic. Note that this
      # class is different than Form. See the comments by the Form class for more
      # information. Any improvements to the form API should be made to *this*
      # class, not to the Form class.
      default_renderer = None
      field_order = None
      prefix = None
      use_required_attribute = True
  
      def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                   initial=None, error_class=ErrorList, label_suffix=None,
                   empty_permitted=False, field_order=None, use_required_attribute=None, renderer=None):
          self.is_bound = data is not None or files is not None
          self.data = data or {}
          self.files = files or {}
          self.auto_id = auto_id
          if prefix is not None:
              self.prefix = prefix
          self.initial = initial or {}
          self.error_class = error_class
          # Translators: This is the default suffix added to form field labels
          self.label_suffix = label_suffix if label_suffix is not None else _(':')
          self.empty_permitted = empty_permitted
          self._errors = None  # Stores the errors after clean() has been called.
  
          # The base_fields class attribute is the *class-wide* definition of
          # fields. Because a particular *instance* of the class might want to
          # alter self.fields, we create self.fields here by copying base_fields.
          # Instances should always modify self.fields; they should not modify
          # self.base_fields.
          self.fields = copy.deepcopy(self.base_fields)
          self._bound_fields_cache = {}
          self.order_fields(self.field_order if field_order is None else field_order)
  
          if use_required_attribute is not None:
              self.use_required_attribute = use_required_attribute
  
          # Initialize form renderer. Use a global default if not specified
          # either as an argument or as self.default_renderer.
          if renderer is None:
              if self.default_renderer is None:
                  renderer = get_default_renderer()
              else:
                  renderer = self.default_renderer
                  if isinstance(self.default_renderer, type):
                      renderer = renderer()
          self.renderer = renderer
  
      def order_fields(self, field_order):
          """
          Rearranges the fields according to field_order.
  
          field_order is a list of field names specifying the order. Fields not
          included in the list are appended in the default order for backward
          compatibility with subclasses not overriding field_order. If field_order
          is None, all fields are kept in the order defined in the class.
          Unknown fields in field_order are ignored to allow disabling fields in
          form subclasses without redefining ordering.
          """
          if field_order is None:
              return
          fields = OrderedDict()
          for key in field_order:
              try:
                  fields[key] = self.fields.pop(key)
              except KeyError:  # ignore unknown fields
                  pass
          fields.update(self.fields)  # add remaining fields in original order
          self.fields = fields
  
      def __str__(self):
          return self.as_table()
  
      def __repr__(self):
          if self._errors is None:
              is_valid = "Unknown"
          else:
              is_valid = self.is_bound and not bool(self._errors)
          return '<%(cls)s bound=%(bound)s, valid=%(valid)s, fields=(%(fields)s)>' % {
              'cls': self.__class__.__name__,
              'bound': self.is_bound,
              'valid': is_valid,
              'fields': ';'.join(self.fields),
          }
  
      def __iter__(self):
          for name in self.fields:
              yield self[name]
  
      def __getitem__(self, name):
          "Returns a BoundField with the given name."
          try:
              field = self.fields[name]
          except KeyError:
              raise KeyError(
                  "Key '%s' not found in '%s'. Choices are: %s." % (
                      name,
                      self.__class__.__name__,
                      ', '.join(sorted(f for f in self.fields)),
                  )
              )
          if name not in self._bound_fields_cache:
              self._bound_fields_cache[name] = field.get_bound_field(self, name)
          return self._bound_fields_cache[name]
  
      @property
      def errors(self):
          "Returns an ErrorDict for the data provided for the form"
          if self._errors is None:
              self.full_clean()
          return self._errors
  
      def is_valid(self):
          """
          Returns True if the form has no errors. Otherwise, False. If errors are
          being ignored, returns False.
          """
          return self.is_bound and not self.errors
  
      def add_prefix(self, field_name):
          """
          Returns the field name with a prefix appended, if this Form has a
          prefix set.
  
          Subclasses may wish to override.
          """
          return '%s-%s' % (self.prefix, field_name) if self.prefix else field_name
  
      def add_initial_prefix(self, field_name):
          """
          Add a 'initial' prefix for checking dynamic initial values
          """
          return 'initial-%s' % self.add_prefix(field_name)
  
      def _html_output(self, normal_row, error_row, row_ender, help_text_html, errors_on_separate_row):
          "Helper function for outputting HTML. Used by as_table(), as_ul(), as_p()."
          top_errors = self.non_field_errors()  # Errors that should be displayed above all fields.
          output, hidden_fields = [], []
  
          for name, field in self.fields.items():
              html_class_attr = ''
              bf = self[name]
              # Escape and cache in local variable.
              bf_errors = self.error_class([conditional_escape(error) for error in bf.errors])
              if bf.is_hidden:
                  if bf_errors:
                      top_errors.extend(
                          [_('(Hidden field %(name)s) %(error)s') % {'name': name, 'error': force_text(e)}
                           for e in bf_errors])
                  hidden_fields.append(str(bf))
              else:
                  # Create a 'class="..."' attribute if the row should have any
                  # CSS classes applied.
                  css_classes = bf.css_classes()
                  if css_classes:
                      html_class_attr = ' class="%s"' % css_classes
  
                  if errors_on_separate_row and bf_errors:
                      output.append(error_row % force_text(bf_errors))
  
                  if bf.label:
                      label = conditional_escape(force_text(bf.label))
                      label = bf.label_tag(label) or ''
                  else:
                      label = ''
  
                  if field.help_text:
                      help_text = help_text_html % force_text(field.help_text)
                  else:
                      help_text = ''
  
                  output.append(normal_row % {
                      'errors': force_text(bf_errors),
                      'label': force_text(label),
                      'field': str(bf),
                      'help_text': help_text,
                      'html_class_attr': html_class_attr,
                      'css_classes': css_classes,
                      'field_name': bf.html_name,
                  })
  
          if top_errors:
              output.insert(0, error_row % force_text(top_errors))
  
          if hidden_fields:  # Insert any hidden fields in the last row.
              str_hidden = ''.join(hidden_fields)
              if output:
                  last_row = output[-1]
                  # Chop off the trailing row_ender (e.g. '</td></tr>') and
                  # insert the hidden fields.
                  if not last_row.endswith(row_ender):
                      # This can happen in the as_p() case (and possibly others
                      # that users write): if there are only top errors, we may
                      # not be able to conscript the last row for our purposes,
                      # so insert a new, empty row.
                      last_row = (normal_row % {
                          'errors': '',
                          'label': '',
                          'field': '',
                          'help_text': '',
                          'html_class_attr': html_class_attr,
                          'css_classes': '',
                          'field_name': '',
                      })
                      output.append(last_row)
                  output[-1] = last_row[:-len(row_ender)] + str_hidden + row_ender
              else:
                  # If there aren't any rows in the output, just append the
                  # hidden fields.
                  output.append(str_hidden)
          return mark_safe('\n'.join(output))
  
      def as_table(self):
          "Returns this form rendered as HTML <tr>s -- excluding the <table></table>."
          return self._html_output(
              normal_row='<tr%(html_class_attr)s><th>%(label)s</th><td>%(errors)s%(field)s%(help_text)s</td></tr>',
              error_row='<tr><td colspan="2">%s</td></tr>',
              row_ender='</td></tr>',
              help_text_html='<br /><span class="helptext">%s</span>',
              errors_on_separate_row=False)
  
      def as_ul(self):
          "Returns this form rendered as HTML <li>s -- excluding the <ul></ul>."
          return self._html_output(
              normal_row='<li%(html_class_attr)s>%(errors)s%(label)s %(field)s%(help_text)s</li>',
              error_row='<li>%s</li>',
              row_ender='</li>',
              help_text_html=' <span class="helptext">%s</span>',
              errors_on_separate_row=False)
  
      def as_p(self):
          "Returns this form rendered as HTML <p>s."
          return self._html_output(
              normal_row='<p%(html_class_attr)s>%(label)s %(field)s%(help_text)s</p>',
              error_row='%s',
              row_ender='</p>',
              help_text_html=' <span class="helptext">%s</span>',
              errors_on_separate_row=True)
  
      def non_field_errors(self):
          """
          Returns an ErrorList of errors that aren't associated with a particular
          field -- i.e., from Form.clean(). Returns an empty ErrorList if there
          are none.
          """
          return self.errors.get(NON_FIELD_ERRORS, self.error_class(error_class='nonfield'))
  
      def add_error(self, field, error):
          """
          Update the content of `self._errors`.
  
          The `field` argument is the name of the field to which the errors
          should be added. If its value is None the errors will be treated as
          NON_FIELD_ERRORS.
  
          The `error` argument can be a single error, a list of errors, or a
          dictionary that maps field names to lists of errors. What we define as
          an "error" can be either a simple string or an instance of
          ValidationError with its message attribute set and what we define as
          list or dictionary can be an actual `list` or `dict` or an instance
          of ValidationError with its `error_list` or `error_dict` attribute set.
  
          If `error` is a dictionary, the `field` argument *must* be None and
          errors will be added to the fields that correspond to the keys of the
          dictionary.
          """
          if not isinstance(error, ValidationError):
              # Normalize to ValidationError and let its constructor
              # do the hard work of making sense of the input.
              error = ValidationError(error)
  
          if hasattr(error, 'error_dict'):
              if field is not None:
                  raise TypeError(
                      "The argument `field` must be `None` when the `error` "
                      "argument contains errors for multiple fields."
                  )
              else:
                  error = error.error_dict
          else:
              error = {field or NON_FIELD_ERRORS: error.error_list}
  
          for field, error_list in error.items():
              if field not in self.errors:
                  if field != NON_FIELD_ERRORS and field not in self.fields:
                      raise ValueError(
                          "'%s' has no field named '%s'." % (self.__class__.__name__, field))
                  if field == NON_FIELD_ERRORS:
                      self._errors[field] = self.error_class(error_class='nonfield')
                  else:
                      self._errors[field] = self.error_class()
              self._errors[field].extend(error_list)
              if field in self.cleaned_data:
                  del self.cleaned_data[field]
  
      def has_error(self, field, code=None):
          if code is None:
              return field in self.errors
          if field in self.errors:
              for error in self.errors.as_data()[field]:
                  if error.code == code:
                      return True
          return False
  
      def full_clean(self):
          """
          Cleans all of self.data and populates self._errors and
          self.cleaned_data.
          """
          self._errors = ErrorDict()
          if not self.is_bound:  # Stop further processing.
              return
          self.cleaned_data = {}
          # If the form is permitted to be empty, and none of the form data has
          # changed from the initial data, short circuit any validation.
          if self.empty_permitted and not self.has_changed():
              return
  
          self._clean_fields()
          self._clean_form()
          self._post_clean()
  
      def _clean_fields(self):
          for name, field in self.fields.items():
              # value_from_datadict() gets the data from the data dictionaries.
              # Each widget type knows how to retrieve its own data, because some
              # widgets split data over several HTML fields.
              if field.disabled:
                  value = self.get_initial_for_field(field, name)
              else:
                  value = field.widget.value_from_datadict(self.data, self.files, self.add_prefix(name))
              try:
                  if isinstance(field, FileField):
                      initial = self.get_initial_for_field(field, name)
                      value = field.clean(value, initial)
                  else:
                      value = field.clean(value)
                  self.cleaned_data[name] = value
                  if hasattr(self, 'clean_%s' % name):
                      value = getattr(self, 'clean_%s' % name)()
                      self.cleaned_data[name] = value
              except ValidationError as e:
                  self.add_error(name, e)
  
      def _clean_form(self):
          try:
              cleaned_data = self.clean()
          except ValidationError as e:
              self.add_error(None, e)
          else:
              if cleaned_data is not None:
                  self.cleaned_data = cleaned_data
  
      def _post_clean(self):
          """
          An internal hook for performing additional cleaning after form cleaning
          is complete. Used for model validation in model forms.
          """
          pass
  
      def clean(self):
          """
          Hook for doing any extra form-wide cleaning after Field.clean() has been
          called on every field. Any ValidationError raised by this method will
          not be associated with a particular field; it will have a special-case
          association with the field named '__all__'.
          """
          return self.cleaned_data
  
      def has_changed(self):
          """
          Returns True if data differs from initial.
          """
          return bool(self.changed_data)
  
      @cached_property
      def changed_data(self):
          data = []
          for name, field in self.fields.items():
              prefixed_name = self.add_prefix(name)
              data_value = field.widget.value_from_datadict(self.data, self.files, prefixed_name)
              if not field.show_hidden_initial:
                  # Use the BoundField's initial as this is the value passed to
                  # the widget.
                  initial_value = self[name].initial
              else:
                  initial_prefixed_name = self.add_initial_prefix(name)
                  hidden_widget = field.hidden_widget()
                  try:
                      initial_value = field.to_python(hidden_widget.value_from_datadict(
                          self.data, self.files, initial_prefixed_name))
                  except ValidationError:
                      # Always assume data has changed if validation fails.
                      data.append(name)
                      continue
              if field.has_changed(initial_value, data_value):
                  data.append(name)
          return data
  
      @property
      def media(self):
          """
          Provide a description of all media required to render the widgets on this form
          """
          media = Media()
          for field in self.fields.values():
              media = media + field.widget.media
          return media
  
      def is_multipart(self):
          """
          Returns True if the form needs to be multipart-encoded, i.e. it has
          FileInput. Otherwise, False.
          """
          for field in self.fields.values():
              if field.widget.needs_multipart_form:
                  return True
          return False
  
      def hidden_fields(self):
          """
          Returns a list of all the BoundField objects that are hidden fields.
          Useful for manual form layout in templates.
          """
          return [field for field in self if field.is_hidden]
  
      def visible_fields(self):
          """
          Returns a list of BoundField objects that aren't hidden fields.
          The opposite of the hidden_fields() method.
          """
          return [field for field in self if not field.is_hidden]
  
      def get_initial_for_field(self, field, field_name):
          """
          Return initial data for field on form. Use initial data from the form
          or the field, in that order. Evaluate callable values.
          """
          value = self.initial.get(field_name, field.initial)
          if callable(value):
              value = value()
          return value
  
  
  class Form(BaseForm, metaclass=DeclarativeFieldsMetaclass):
      "A collection of Fields, plus their associated data."
      # This is a separate class from BaseForm in order to abstract the way
      # self.fields is specified. This class (Form) is the one that does the
      # fancy metaclass stuff purely for the semantic sugar -- it allows one
      # to define a form using declarative syntax.
      # BaseForm itself has no way of designating self.fields.
  