Best approach when implementing Serializers

[PedroDaumas]

Hi everyone, I've recently started using DRF to build an API and it's been great, but I'm not sure how I should go about implementing Serializers for CRUD operations. What is the best approach, have multiple Serializers one for each operation/endpoint? Have a general one with extra logic to remove/add fields depending on the operation?

Although self-explanatory let me show an example of my problem, let's say I have a default user, whenever I'm creating a Sign-Up route there are a few fields that I don't want the person requesting to be able to send, ie: is_superuser or is_staff.
So I create something like this:

class UserSerializer(serializers.ModelSerializer):

    class Meta:
        model = User
        fields = (
            "username",
            "first_name",
            "last_name",
            "email",
            "password",
        )

This should be enough for a Sign-Up route, but now let's say I want to create an Update route. Since username is a unique field I don't want the user to be able to send this field in either PATCH or PUT request, so I need to exclude these fields for said methods. I might also want to have a user send the current password before changing it, and so on.

[TGoddessana]

Personally, I would prefer to write a serializer for every action and override get_serializer_class, or at least separate them (read/write&update).