On Sun, Mar 22, 2015 at 5:16 PM, Joachim Durchholz <j...@durchholz.org> wrote: > Am 22.03.2015 um 22:23 schrieb Aaron Meurer: >> >> Python operations fallback to the reverse operation when they are not >> defined, so e.g., x + y does x.__add__(y) and if that returns >> NotImplemented, it does y.__radd__(x). For the comparison operators, >> it does the flipped operator, so this would be (0).__le__(x + 3), >> which returns NotImplemented, so it then calls (x + 3).__ge__(0), >> which works. > > > Good to know - I was suspecting that that's the case, but wasn't 100% sure. > Is this behaviour documented somewhere? I didn't find any reference to it, > but maybe I'm looking in the wrong spots.
https://docs.python.org/3/reference/datamodel.html#object.__lt__. That page in general is a good reference for all these sorts of things. Aaron Meurer > >> The only downside here is that you end up getting >> >> inequality in the reversed order from what you wanted. > > > No big deal as long as all comparison functions are implemented > consistently, I suppose. > Do I suppose correctly? > > Ah, one trap: Consistency has to be ensured across classes. Not difficult > but requires diligence and quite precise knowledge about Python's comparison > semantics. > Any other traps? > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/550F3F36.7090109%40durchholz.org. > > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6%2BjEzqXtSqkUXcpyw25dW-X199w6KjkeTEKoNHnMg5xBw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
