In Python 2, returning an int where a float was expected could break
existing code (since in Python 2 int and float behave differently under
division), but in Python 3 int is virtually a subclass of float (see PEP
3141). So it's not a crazy idea.
However, it's a bit of a slippery slope. Pretty much everything in the math
module always returns a float. Or do you propose that math.sin(0) also
return 1 instead of 1.0?
Also, how important is it to use this? I suspect the only reason it exists
as a builtin is that it handles -0.0 correctly. But that's really only of
interest to people doing serious floating point stuff. For everyone else,
it's pretty much this one-liner:
def copysign(x, y):
return abs(x) if y >= 0 else -abs(x)
On Thu, Nov 28, 2019 at 4:20 PM Marein <python-id...@marein.net> wrote:
> The math.copysign(x, y) function always returns a float, even when the
> given x is an int, i.e. math.copysign(3, -1) gives -3.0. This is documented
> behaviour, but I find it somewhat surprising given that the name suggests
> that it only copies a sign, and it's also annoying in situations when an
> int is strictly needed (i.e. as the step argument to range), requiring an
> additional cast.
>
> I'm interested to hear whether it might be a good idea to preserve the
> int/float type of the argument in math.copysign.
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