      widget = widgets.TextInput
  
      def __init__(self, source=None, readonly=False, required=None,
                   validators=[], error_messages=None, widget=None,
                   initial=None):
  
          super(WritableField, self).__init__(source=source)
  
          self.readonly = readonly
          if required is None:
 
</s> remove             if getattr(self, 'missing_value', None) is not None:
                native = self.missing_value
 </s> add             if self.default is not None:
                native = self.default </s> remove             if getattr(v, 'initial', None):
                kwargs['initial'] = v.initial
 </s> add             if getattr(v, 'default', None) is not None:
                kwargs['initial'] = v.default
 </s> remove         # These attributes are ony used for HTML forms.
        self.initial = initial

 </s> add         # Widgets are ony used for HTML forms.
                 default=None):
      widget = widgets.TextInput
  
      def __init__(self, source=None, readonly=False, required=None,
                   validators=[], error_messages=None, widget=None,
                 default=None):
  
          super(WritableField, self).__init__(source=source)
  
          self.readonly = readonly
          if required is None:
keep keep keep keep replace keep keep keep keep keep
 Remove `initial` kwarg, add `default`. 
rest_framework/fields.py