title: django exclude self from queryset for validation
body: <p>I am working with my own clean method to see if some other table already had a field with the same string.
  This all goes fine as long as i am creating one, but when i try to edit it, it find "itself" and gives back the error.
  Now am i wondering how can i exclude the instance itself in my clean method</p>
  
  <pre><code>def clean_name(self):
      raw_data = self.cleaned_data['name']
      data = raw_data.title()
  
      if Country.objects.filter(name=data).exists():
          raise forms.ValidationError(("There is already a country with the name: %s") % data)
      if Province.objects.filter(name=data).exists():
          raise forms.ValidationError(("There is already a province with the name: %s") % data)
      if Region.objects.filter(name=data).exists():
          raise forms.ValidationError(("There is already a region with the name: %s") % data) 
      return data
  </code></pre>
  
  <p>i know there is a .exclude()  but that needs a variable to be passed along with it, not sure how i could get that along with my clean method</p>