On Saturday, July 21, 2018 at 11:28:44 AM UTC-7, Jeroen Demeyer wrote: > > I was benchmarking some code (in particular the density() method of > matrices) and noticed code of the form > > if not x.is_zero(): > > however, that's a lot slower than doing just > > if x: > > So, this makes me wonder: what is the reason for the is_zero() method? > Are there classes where "x.is_zero()" is not the same as "not x"? > > I would think there is a difference in expressed intention: The python bool(x) just asks to convert x to a boolean (implemented via __nonzero__). While custom and the naming of the method suggest it should be roughly something like (x != 0) that's not enforced.
I can imagine that at some point there might be a type out there for which the two do not agree, so if I want to check that something is zero, I'd probably just defensively use is_zero (if I know that method is provided -- I don't think it's a standard python method). >From a stylistic point of view I always dislike "if x:" when x is not obviously a boolean already. It's just not how we write mathematics. However, if code needs to optimized for speed, style quickly goes out the window. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
