你如何为 Python 类中有价值的输入引发 ValueError？

Question

I want to raise an Value Error for negative values of a and b. I have played around with this but it raises ValueError for different values and it does not seem to work properly.

class RightTriangle:
    def __init__(self, a, b):
            self.a = a
            self.b = b
            self.c = np.sqrt(a**2+b**2)

            if (self.a or self.b) < 0:
                raise ValueError("Negative")

Answer 1

Fix:

if self.a < 0 or self.b < 0:

What you've got is evaluating (self.a or self.b) first. What this first part is doing is this:

if self.a: # anything but 0 is True
    return self.a
else:
    return self.b

So, you're probably going to get self.a most of the time, and then it's going to be compared in < 0 .