On consideration, this has sat for so long it can sit a bit longer. We have more than enough to try and get in for 3.7 so defer this to 3.8.

Does this mean ArtistList does not work anymore? It seems like starting from 3.7.0, pop() function doesn't work on it...

That has nothing to do with this PR; see https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.7.0.html#modification-of-axes-children-sublists

Ah ok, thank you.

Is this really necessary? I could imagine a use case where one has a GUI with multiple Axes and functionality to move datasets across Axes. That would be significantly more complicated if one had to read all properties from an Artist and create a new one with the same properties.

IMHO „ but it is not clear we actually do enough clean up to make these re-added Aritsts actually work.“ is not enough justification for prohibiting. It rather shows that our architecture is not clear. Overall, I suppose Artists hold little Axes-specific information, and I don’t see a fundamental blocker why we shouldn’t be able to systematically separate that. I‘d rather go with „re-adding is permitted but not well-tested behavior.“ and handle issues when they arise, either by fixing or by prohibiting re-use of specific Artists, when there are good reasons for it.

I‘d rather go with „re-adding is permitted but not well-tested behavior.“ and handle issues when they arise, either by fixing or by prohibiting re-use of specific Artists, when there are good reasons for it.

ok, I'm sold on that. I've been dragging this PR along for a while now without thinking through why to begin with 🐑 . I think three things have changed in the last few years:

1. we did deprecate settable ArtistList so artists only get added through a path where we can update their state (which eliminates a set of issues where the artist has transforms from the wrong axis)
2. we have gotten much better about breaking the loops on remove (driven by helping gc not need to wait for the cyclic passes to release memory)
3. some of the work with @ksunden we are looking at make Artist more relocatable and locking this down hard to just re-open it not the best plan

I'll go head and close this and we can use #31748 to sort out the current state.