无法从子类调用父类方法

Question

I've started trying to learn Python after working with Java for the past year and decided to work on a couple class projects I've done and to write them in Python. I am getting an AttributeError at line 102, stating my super object has no attribute 'area'.

I've looked through different posts of how it's done, and I can't seem to figure out why this isn't working correctly for me after following other solutions.

It's a simple program that takes in input from the user, parses it, then depending on the shape type, will call the methods of the appropriate object type, then calculates and prints it out. For example, an input would be "R 3/4 5-7", supposed to weigh 8.37, or "P 1/4 5-6 2-3", supposed to weigh 126.07.

import math

class Shipment:
    _weight = 0

    def weight(self):
        return self._weight

    def frac_in_feet(self, frac):
        thick_frac = frac.replace('/', "")
        print("number is: ", thick_frac)
        numerator = int(thick_frac[0])
        denominator = int(thick_frac[1])
        fraction_of_an_inch = numerator / denominator

        return self.in_feet(0, fraction_of_an_inch)

    def feet_and_inches_in_feet(self, feet_and_inches):
        a = feet_and_inches.replace('-', "")
        print("number is: ", a)
        feet = int(a[0])
        inches = int(a[1])

        return self.in_feet(feet, inches)

    def in_feet(self, feet, inches):
        inches /= 12
        print(feet + inches)
        return feet + inches

    def get_value_in_feet(self, str):
        i = str.find('/')
        j = str.find('-')

        if i == -1:
            value = self.feet_and_inches_in_feet(str)

        if j == -1:
            value = self.frac_in_feet(str)

        return value

    def add_item(self, quantity, description):
        desc_values = description.replace(" ", "")
        values = []
        shape_letter = desc_values[0]
        i = 1
        j = 4
        for r in range(int(len(desc_values) / 3)):
            print("r is: ", r)
            values.append(self.get_value_in_feet(desc_values[i:j]))

            i += 3
            j += 3

        if shape_letter == 'P':
            if len(values) != 3:
                raise ValueError("Plate needs three dimensions. ")

            shape = Plate(values[0], values[1], values[2])

        elif shape_letter == 'R':
           if len(values) != 2:
               raise ValueError("Rod needs two dimensions")

           shape = Rod(values[0], values[1])

        else:
            raise ValueError("Shape letter ", shape_letter, " not recognized.")

        self._weight += quantity * shape.weight()
        return shape





class SteelShape:
    _length = 0
    _weight = 0

    def length(self, length):
        _length = length

    def length(self):
        return self._length

    def weight(self, weight):
        self._weight = weight

    def weight(self):
        return self._weight

class CalcShape(SteelShape):
    _area = 0

    def area(self, area):
        self._area = area

    def weight(self):
        return self._area * self.length() * 489





class Rod(CalcShape):
    def __init__(self, diameter, length):
        radius = diameter / 2
        super(CalcShape, self).area(math.pi * radius**2)
        super(CalcShape, self).length





class Plate(CalcShape):
    def __init__(self, thick, width, length):
        super(CalcShape, self).area(thick * width)
        super(SteelShape, self).length(length)

values = []
shipment = Shipment()
shape = SteelShape()
line = input("Enter shape and dimensions: ")
shape = shipment.add_item(1, line)
if isinstance(shape, Plate):
    print("Plate weighs ", shape.weight())

elif isinstance(shape, Rod):
    print("Rod weighs ", shape.weight())


print("Total shipment weight: ", shipment.weight())
# R 3/4 5-7: supposed to weigh 8.37
# P 1/4 5-6 2-3: supposed to weigh 126.07

Answer 1

I think replacing the super and instead using staticmethod is a better choice. See here:

https://stackoverflow.com/a/735978/10416716

Hope this helps.