On Thu, Sep 19, 2019 at 03:26:27PM +1000, Chris Angelico wrote: > On Thu, Sep 19, 2019 at 3:08 PM Richard Higginbotham <higgi...@gmail.com> > wrote: > > > > I'm not sure if there is any interest by others but I have frequently come > > across cases where I would like to compare items in one list in another > > similar to relational algebra. For example are the file names in A in B and > > if so return a new list with those items. Long story short, I wrote some > > functions to do that. They are quite simple and fast (due to timsort in no > > small part). Even the plain python code is faster than the built in set > > functions (afaik). I created a github and put the ones I thought the > > community might like in there. https://github.com/ponderpanda/listex > > > > an example would be > > a = [1,2,3,4,5,6] > > b = [1,3,7,4] > > list_intersection(a,b, sorta=True, sortb=True) > > > > returns [1,3,4] > > Can you elaborate on how this differs from using the built-in set type > for set operations? eg is this for situations where the values are not > all hashable?
Sets are unordered and can contain no duplicates. Lists are ordered and can contain duplicates, so you might think of them as "ordered multisets". I can't say I'm very enthusiastic about that "sorta, sortb" API, and I'm rather surprised about Richard's claim that a pure-Python list intersection is faster than set intersection written in C (but maybe Richard is a better programmer than me). But I'd like to hear more about this proposal. -- Steven _______________________________________________ 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/IVC4345635ZE366CRZQEQPGX4LQD5WC6/ Code of Conduct: http://python.org/psf/codeofconduct/
