Yes, everyone who designs a sorted container library runs into the fact that a SortedList is a Sequence, and mutable, but not even close to a MutableSequence—it’s not just append and extend; you can’t even do __setitem__. In fact, it’s a lot closer to a MutableSet (assuming you use the obvious names add and update), but it’s not that either, because it’s a multiset rather than a set.
I believe SortedContainers 2.x’s SortedList inherits MutableSequence anyway, and raises NotImplementedError on __setitem__, append, etc. Which is a weird compromise, sometimes confusing but sometimes handy.
There's a gitHUb issue about that -- not sure how it will be resolved. Personally a bigger fan of EAFTP Duck Typing than ABCs and isinstance(), but if you are going to inherit form an ABC, it should be correct :-) Otherwise it really kinda kills the point of any kind of type checking (dynamic or static), no?
I think the best solution is to just not have a SortedList.
Interesting -- I wonder if the SortedContainers folks have any idea how often it's used.
90% of the use cases for SortedContainers and its competitors are dicts.
No idea how to know for sure, but it's a lot easier ta add one, and wait to see if anyone clammers for more, than to add a bunch that are rarely used., and have to maintain or deprecate them.
So it seems we have a pretty simple proposal here:
Add SortedDict, much like implemented in the SortedContainers package, to the standard library's collections module.
Now we just need someone to champion it.
Oddly, I don't think the OP has responded at all to this thread :-)
-CHB