Django admin: make field editable in add but not edit

Question

I've got a model similar to this:

class Product(models.Model):     third_party_id = models.CharField(max_length=64, blank=False, unique=True) 

that uses the Django default primary key. I want users to be able to add products by setting the third_party_id on the add page, but I don't want that field editable in the edit page to avoid corrupting the third_party_id. In the Django docs, the same settings appear to be used for add and edit. Is this possible?

Answer 1

Do not set self.readonly_fields to avoid thread issues. Instead override get_readonly_fields method:

def get_readonly_fields(self, request, obj=None):     if obj: # obj is not None, so this is an edit         return ['third_party_id',] # Return a list or tuple of readonly fields' names     else: # This is an addition         return [] 

Answer 2

The above is helpful (shanyu's answer using get_readonly_fields), however it does not work properly if used in "StackedInline". The result is two copies of whatever field is marked readonly, and it is not editable in the "add" instance. See this bug: https://code.djangoproject.com/ticket/15602

Hope this saves someone some searching!