Inheritance problem

[deanhystad]

Overwriting is not the right term in this case. Your geometry class inherits from two classes that both have a "surface" method. When calling geometry.surface() which method is used? In your case it uses sphere.surface() because Sphere appears first in
class geometry(sphere,cube):. The geometry.mro() would show the order.

I don't think you want geometry to be a subclass of sphere and cube. Instead I think you want it to be their superclass. Inheritence should be from the generic to the specific. The superclass of sphere should be more generic than a sphere.

import math

class geometry:
    """base class for geometetric shapes"""
    def surface(self):
        """Return surface area"""
        raise NotImplementedError('Subclass responsibility')

class sphere(geometry):
    def __init__(self, radius):
        self.radius = radius

    def surface(self):
        return 4 * math.pi * self.radius * self.radius

class cube(geometry):
    def __init__(self, edge):
        self.edge = edge

    def surface(self):
        return 6 * self.edge * self.edge

shapes = [sphere(3), cube(3), cube(5), sphere(6)]

for shape in shapes:
    print(shape.surface())