New submission from Martijn Pieters <m...@python.org>:
Currently, the sorting HOWTO at https://docs.python.org/3/howto/sorting.html#odd-and-ends contains the text: > The sort routines are guaranteed to use __lt__() when making comparisons > between two objects. So, it is easy to add a standard sort order to a class > by defining an __lt__() method Nowhere else in the Python documentation is this guarantee made, however. That sort currently uses __lt__ only is, in my opinion, an implementation detail. The above advice also goes against the advice PEP 8 gives: > When implementing ordering operations with rich comparisons, it is best to > implement all six operations (__eq__, __ne__, __lt__, __le__, __gt__, __ge__) > rather than relying on other code to only exercise a particular comparison. > > To minimize the effort involved, the functools.total_ordering() decorator > provides a tool to generate missing comparison methods. The 'guarantee' seems to have been copied verbatim from the Wiki version of the HOWTO in https://github.com/python/cpython/commit/0fe095e87f727f4a19b6cbfd718d51935a888740, where that part of the Wiki page was added by an anonymous user in revision 44 to the page: https://wiki.python.org/moin/HowTo/Sorting?action=diff&rev1=43&rev2=44 Can this be removed from the HOWTO? ---------- assignee: docs@python components: Documentation messages: 332949 nosy: docs@python, mjpieters, rhettinger priority: normal severity: normal status: open title: Remove 'guarantee' that sorting only relies on __lt__ from sorting howto versions: Python 3.6 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35654> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
