Class exceptions

[DPaul]

Hi,
Question without code, I'm looking for best practice.
Simplified: a program imports a class "sphere.py".
In sphere.py, 3 functions: Circonf(), Volume(), surface()
These calculations are called with the diameter as an argument.
ball = sphere(5)
v= ball.Volume() ....
Question:
What if sphere is called with a wrong argument (negative or string or zero...),
it generates an error in the class, but how will the main program know?
-
Should I simply put a try-except in the class and return some error code?
Or is there a more appropriate solution to this problem.
thx,
Paul

[Gribouillis]

I think the best solution is to raise an exception when there is an error. This leaves client code free to catch the exception or to let it propagate or to ensure that the argument is always correct. So I suggest

class Sphere:
    def __init__(self, radius):
        if radius < 0:
            raise ValueError('Non negative radius expected, got', radius)
        ...