Conditional use of

So I have a class that remembers its instances based on an ID. When unpickling such an object there are two cases I'd like to handle:

No other instance with that ID exists, so a new instance is generated and __setstate__ should be called normally.

When another instance of that ID exists, that object is returned and I want to avoid calling __setstate__ on it.

Please take a look at this class definition.

You will notice that currently I update only attributes that evaluate to False as a workaround.

I can think of two general strategies to solve this:

As in this previous answer, I could define another function that is called with the result from __getnewargs__ and attach some attribute that tells me whether to run __setstate__ or not.

If I can tell whether the class' __call__ method was called from within pickle I could do the same.

I do not know if it's possible to further interfere with the pickling machinery and I don't want to subclass the unpickler.

Thoughts, recommendations, completely different solutions? Thank you.

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