Python Forum

Hello everyone,
I've got problem with assertion. It seems that it should work, but after running the program I receive AssertionError. Do you have any idea why and how I can fix it/modify declaration of classes?
This is my code:

class Figure1:
    def __init__(self, x, y, z):
        self._x = x
        self._y = y
        self._z = z
    @property
    def area(self):
        return (self._x + self._y) * self._z / 2
class Figure2(Figure1):
    def __init__(self, x, z):
        super().__init__(x=x, y=x, z=z)
class Figure3(Figure2):
    @property
    def circumference(self):
        return self._x * 4

class Figure4(Figure2):

    def __init__(self, x, y):
        super().__init__(x=x,z=y)
    @property
    def circumference(self):
        return 2 * self._x + 2 * self._z

class Figure5(Figure4, Figure3):

    def __init__(self, x):
        super().__init__(x=x, y=x)

a = Figure5(9).area
print(a)
b = Figure5(9).circumference
print(b)
if __name__ == "__main__":
    Figure5.x = 9
    assert Figure5.circumference == 36
    assert Figure5.area == 81

and the error:

Error:
81.0
Traceback (most recent call last):
36
line 37, in <module>
    assert Figure5.circumference == 36
AssertionError

Process finished with exit code 1

You should be creating a Figure5 instance: check = Figure5(5). Run your assertions on that. Currently you are testing the class itself.

"Figure5" is a class, not an instance of a class. As such, there is no "self" to provide to circumference(). If you remove the property annotation from circumference, a second error appears because of the lack of self. You need to instantiate the class and then call circumference to make it work.

On a side note, you may encounter issues with Figure5 because of multiple inheritance because both of its parents have a circumference method.

class Figure1:
    def __init__(self, x, y, z):
        self._x = x
        self._y = y
        self._z = z

    def area(self):
        return (self._x + self._y) * self._z / 2

class Figure2(Figure1):
    def __init__(self, x, z):
        super().__init__(x=x, y=x, z=z)

class Figure3(Figure2):
    
    def circumference(self):
        return self._x * 4

class Figure4(Figure2):

    def __init__(self, x, y):
        super().__init__(x=x,z=y)

    def circumference(self):
        return 2 * self._x + 2 * self._z

class Figure5(Figure4, Figure3):

    def __init__(self, x):
        super().__init__(x=x, y=x)
 
a = Figure5(9)
print(a.area())
print(a.circumference())

if __name__ == "__main__":
    a.x = 9
    assert a.circumference() == 36
    assert a.area() == 81