Check if two values are both non-negative or both negative

Question

Given a pair of integer values, I need to check if both are non-negative or both are negative.

The trivial way is:

def func(a, b):
    return (a >= 0 and b >= 0) or (a < 0 and b < 0)

But I am looking for something "neater", which I believe to be possible, so I came up with this:

def func(a, b):
    return (a >= 0) ^ (b >= 0) == 0

However, this one feels a little "obscure to the average reader".

Is there a cleaner way?

cs95 · Accepted Answer · 2018-03-06T11:57:39.300

13

Multiply them and test against 0:

def func(a, b):
    return a * b >= 0

edited Mar 06 '18 at 11:57

answered Mar 06 '18 at 11:53

cs95

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Thank you. Is this agnostic to integer size? I am dealing with extremely large values. – goodvibration Mar 06 '18 at 11:58
1

@goodvibration yes, python ints have no limit besides your system memory. – cs95 Mar 06 '18 at 11:58
@goodvibration Python integers are always arbitrary precision, so no overflow. – Zinki Mar 06 '18 at 11:59
@monamona Hmm, here's [another question](https://stackoverflow.com/q/45164645/4909087) for which I though the answer to be obvious, but apparently not, judging by the votes on the accepted answer :) – cs95 Mar 06 '18 at 12:00
@cᴏʟᴅsᴘᴇᴇᴅ I correct myself. You are an absolute genious! Maybe you are not concerned by "déformation professionelle"... – monamona Mar 06 '18 at 14:39

score 3 · Answer 2 · answered Mar 06 '18 at 11:57

This is Python. We're not about the most concise efficient possible way to do things in all cases - that's for the C++ lads to do.

If (a >= 0 and b >= 0) or (a < 0 and b < 0) is "fast enough", (which would surprise me if not the case), then stick with it. It works, and is VERY obvious what it does.

For either your second solution, or @coldspeed's, I personally would have to write some stuff down on paper to figure out what it's doing, unless the function name was a LOT better than func.

Check if two values are both non-negative or both negative

2 Answers2