old_contents: import os
  from django.db import models
  from django.forms.models import model_to_dict
  from observer.event_manager import EventSender
  
  
  class PlCoreBase(models.Model):
  
      created = models.DateTimeField(auto_now_add=True)
      updated = models.DateTimeField(auto_now=True)
      enacted = models.DateTimeField(null=True, default=None)
  
      class Meta:
          abstract = True
          app_label = "core"
  
      def __init__(self, *args, **kwargs):
          super(PlCoreBase, self).__init__(*args, **kwargs)
          self.__initial = self._dict
  
      @property
      def diff(self):
          d1 = self.__initial
          d2 = self._dict
          diffs = [(k, (v, d2[k])) for k, v in d1.items() if v != d2[k]]
          return dict(diffs)
  
      @property
      def has_changed(self):
          return bool(self.diff)
  
      @property
      def changed_fields(self):
          return self.diff.keys()
  
      def get_field_diff(self, field_name):
          return self.diff.get(field_name, None)
  
      def delete(self, *args, **kwds):
          super(PlCoreBase, self).delete(*args, **kwds)
  
          EventSender().fire({'delete_flag':True,'model':self.__name__})
  
      def save(self, *args, **kwargs):
          super(PlCoreBase, self).save(*args, **kwargs)
          
          # Tell the observer that the source database has been updated
          EventSender().fire()
  
          self.__initial = self._dict
  
      @property
      def _dict(self):
          return model_to_dict(self, fields=[field.name for field in
                               self._meta.fields])
  
  
  
  
new_contents: import os
  from django.db import models
  from django.forms.models import model_to_dict
  from observer.event_manager import EventSender
  
  
  class PlCoreBase(models.Model):
  
  	created = models.DateTimeField(auto_now_add=True)
  	updated = models.DateTimeField(auto_now=True)
  	enacted = models.DateTimeField(null=True, default=None)
  
  	class Meta:
  		abstract = True
  		app_label = "core"
  
  	def __init__(self, *args, **kwargs):
  		super(PlCoreBase, self).__init__(*args, **kwargs)
  		self.__initial = self._dict
  
  	@property
  	def diff(self):
  		d1 = self.__initial
  		d2 = self._dict
  		diffs = [(k, (v, d2[k])) for k, v in d1.items() if v != d2[k]]
  		return dict(diffs)
  
  	@property
  	def has_changed(self):
  		return bool(self.diff)
  
  	@property
  	def changed_fields(self):
  		return self.diff.keys()
  
  	def get_field_diff(self, field_name):
  		return self.diff.get(field_name, None)
  
  	def delete(self, *args, **kwds):
  		super(PlCoreBase, self).delete(*args, **kwds)
  
  		try:
  			EventSender().fire({'delete_flag':True,'model':self.__name__})
  		except:
  			# Investigate later. 
  			pass
  
  
  	def save(self, *args, **kwargs):
  		super(PlCoreBase, self).save(*args, **kwargs)
  		
  		# Tell the observer that the source database has been updated
  		EventSender().fire()
  
  		self.__initial = self._dict
  
  	@property
  	def _dict(self):
  		return model_to_dict(self, fields=[field.name for field in
  							 self._meta.fields])
  
  
  
  
subject: Make change to Model code failsafe