Home / Questions / 221296
Accepted
Jesus_jbs
Asked: 2020-12-12 09:24:49 +0800 CST 2020-12-12 09:24:49 +0800 CST

What function does the following code serve? python

  • 772

I have the following code:

numeros = [-1.4, 2.3, 5.27, -3.5, 2.9, 3.12]
lista = [(x > 0) - (x < 0) for x in numeros]
print(lista)

And it returns the following:

[-1, 1, 1, -1, 1, 1]

The question is what function it fulfills (x > 0) - (x < 0)and how I could interpret it. Thanks in advance.

python

1 Answers

  1. Best Answer

    If xit is positive, then it (x>0)will be Truewhile (x<0)will be False, so it (x>0)-(x<0)will be evaluated as True - False. Since booleans cannot be subtracted, Python will treat them as 1 - 0, and the result will be 1.

    If xit is negative, you can analogously see that the result will be-1

    And there is still another case . If xit is zero, then both (x>0)are (x<0)false, so the result in this case will be 0.

    So all that expression behaves like a kind of sign function , which python does not have implemented by default (although numpy does implement it ) .

    The same using a ternary operator would be -1 if x<0 else 1 if x>0 else 0. I personally think this one is clearer, and probably even more efficient.

    • 0