[Python-ideas] Re: math.copysign not to introduce float

[Guido]

I suspect Tim Peters had a good reason to include copysign() rather than sign().

Tim wasn't involved in this one :-) But copysign is a "recommended" function in IEEE-754, and was eventually added to the C standard (for libm). So supplying it in `math` was really a no-brainer for whoever did it (guessing it was Mark Dickinson, but don't really know).