      default = None
  
      def __init__(self, source=None, read_only=False, required=None,
                   validators=[], error_messages=None, widget=None,
                   default=None):
  
          super(WritableField, self).__init__(source=source)
  
          self.read_only = read_only
          if required is None:
 
</s>
                 default=None, blank=None):
      default = None
  
      def __init__(self, source=None, read_only=False, required=None,
                   validators=[], error_messages=None, widget=None,
                 default=None, blank=None):
  
          super(WritableField, self).__init__(source=source)
  
          self.read_only = read_only
          if required is None:
keep keep keep keep replace keep keep keep keep keep
 Merge fixes for 'blank=True' fields.  Fixes #324, Fixes #325

Thanks to @Roarster.
rest_framework/fields.py