duplicated data

how can I prevent user to save the same data twice in from from models!

Write a custom save method on your model to check to see if an existing model already has the data being submitted. If it’s just one or two fields that need to be unique, you could apply a unique constraint in the model.

thank you so much
I use “from django.core.exceptions import ObjectDoesNotExist”
but your suggestion looks more useful
thank you so much