python - Modify variable just in the Django admin but not in database -

i want modify single value when open instance of model in django admin.
want display value opposite of 1 stored in database. here did in admin.py :

class mymodeladminform(forms.modelform):     import_file = forms.filefield(required=false)      class meta:         model = mymodel      def __init__(self, *args, **kwargs):         super(mymodeladminform, self).__init__(*args, **kwargs)         print(self.instance.value)         self.instance.value = self.instance.get_reverted_value()         print(self.instance.value) 

i works can see prints, admin still displays original value stored in database.
idea ?
in advance

what about:

def __init__(self, *args, **kwargs):     super(mymodeladminform, self).__init__(*args, **kwargs)     self.fields['value'].value = self.instance.get_reverted_value()