On Apr 29, 2020, at 08:33, Christopher Barker <python...@gmail.com> wrote: > > I've wondered about Linked Lists for a while, but while there are many > versions on PyPi, I can't find one that seems to be mature and maintained. > Which seems to indicate that there isn't much demand for them.
I think there’s lots of demand for them, but there are so many different variants that can’t substitute for each other (try taking any nontrivial sample code using Haskell’s single-linked, no-handle, immutable tail-sharing list and rewriting it with C++’s doubly-linked handled mutable list, or vice-versa), and most of the key operations fit so poorly with Python’s sequence/iterable API, and they’re all so easy to build, that people just build the one they need whenever they need it. I do have a few different linked lists in my toolbox that have come up often enough that I stashed them (an immutable cons, a handled double-linked list, a cffi wrapper for a common style of C internally-linked lists, probably others), but half the time I reach for one I have to modify it anyway, so I haven’t bothered to turn them into a package I just import and use. And, while I did add the whole (Mutable)Sequence API to each one (because it’s convenient for debugging and REPL exploration to be able to list(xs), or to get a repr that’s written in terms of a from_iter classmethod so I can eval it back, etc.), I usually don’t use that API for anything but debugging. When you’re dealing with linked lists, you usually need to deal with the nodes directly. For example, one big reason to use linked lists is constant-time splicing, but you can’t splice in constant time if all you have is the head/handle and/or an opaque iterator that only knows how to go forward; you need the node before the splice point (or, for doubly-linked, after is fine too). Another reason to use (Lisp/Haskell-style) linked lists is that they automatically release nodes as you iterate unless you keep a reference to the head, but that’s clumsy to do with Python-style APIs. And so on. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/DGBRHXGXHAMERZRQW2WN5XMU22WBIHUK/ Code of Conduct: http://python.org/psf/codeofconduct/
