Géry <gery.o...@gmail.com> added the comment: More precisely:
The following relationships are always valid and therefore implemented by default in Python (_except for the union relationships, which seems arbitrary and is the reason of this Python issue_): - 2 [complementary](https://en.wikipedia.org/wiki/Binary_relation#Complement) relationships: "= and ≠ are each other’s complement"; - 6 [converse](https://en.wikipedia.org/wiki/Binary_relation#Converse) relationships*: "= is the converse of itself", "≠ is the converse of itself", "< and > are each other’s converse", and "≤ and ≥ are each other’s converse"; - 2 [union](https://en.wikipedia.org/wiki/Binary_relation#Union) relationships: "≤ is the union < and =" and "≥ is the union of > and ≤". The following relationships are only valid for [total orders](https://en.wikipedia.org/wiki/Binary_relation#Properties) and therefore not implemented by default in Python (but users can conveniently implement them when they are valid with the [`functools.total_ordering`](https://docs.python.org/3/library/functools.html#functools.total_ordering) class decorator provided by the Python standard library): - 4 [complementary](https://en.wikipedia.org/wiki/Binary_relation#Complement) relationships: "< and ≥ are each other’s complement" and "> and ≤ are each other’s complement". ---- \* Converse relationships are implemented in Python through the [`NotImplemented` protocol](https://docs.python.org/3/reference/datamodel.html#the-standard-type-hierarchy). ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue39862> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
