class Vector:
x = PositiveNumber(0)
y = PositiveNumber(0)
z = PositiveNumber(0)
def __init__(self, x, y, z):
self.x, self.y, self.z = x, y, z
class Thing:
x = PositiveNumber()
class Thing:
x = PositiveNumber(8)
def __init__(self):
self.x = -4
class Thing:
x = PositiveNumber(4)
y = PositiveNumber(5)