I've just made a small update to BagOfStuff, my little support library for my personal Python-based FOSS projects. This release makes some more changes to the history classes, adding an add_or_replace method, and also making some improvements to the type hinting by basing the classes on MutableSequence rather than Sequence.

While the history classes were originally intended to feel immutable, it's obvious that they're really not. The idea was that stuff gets added to them, stuff falls off the other end, and stuff might disappear depending on the context and when stuff gets added. The general idea was that direct manipulation was something that wouldn't happen. So I'd started out with them inheriting from Sequence, and so implying they were a read-only interface.

Given this acknowledgement, they now inherit from MutableSequence. This means that some extra (dunder) methods are added, and it also means that some extra exceptions can be raised. For example: setting slices to iterables isn't supported and will raise a NotImplementedError. Some other slice-based operations aren't supported either.

While this is close to a breaking change, it's fine for my use of this code. However, I had to make one big breaking change: I'd written clear so that it returned Self1. The interface expected by MutableSequence is one that returns None. So to strictly comply with that interface, I've changed the return type.

With this being a breaking change, I've bumped the library version to v2.0.0. While it's really a small change, and only one I'd notice, there's no getting away from the fact that the API has changed. That deserves a major version bump.

  1. I tend to prefer that a method that might return None actually return Self; it allows for chaining. I recognise that there are other schools of thought about this in the Python world; I'm not a member of those schools. ↩