Changing the unknown attributes from a parent class for a child class

Question

I want to create a child class Cell with parent Class pygame.Rect but I cannot get the attribute top of the instance of the class Cell to change and it's just set to zero. My Code is:

import pygame

light = pygame.Color('#D3D3D3')
dark = pygame.Color('#222222')

class Cell(pygame.Rect):
    def __init__(self, index, side):
        self.index = index
        self.side = side
        self.color = None       # Index is a tuple from (0, 0) to (2, 2)
        self.has_pawn = None

        # Setting coordinates
        for i in range(3):
            if index[1] == i:
                self.x = i*self.side
            if index[0] == i:
                self.y == (2-i)*self.side

        self.left = self.x
        self.top = self.y
        self.width = self.side
        self.height = self.side
        
        # self.rect = pygame.Rect(x, y, width, height)

        # Setting color
        sum = self.index[0] + self.index[1]
        if sum % 2 == 0:
            self.color = light
        if sum % 2 == 1:
            self.color = dark

        # Setting has_pawn
        if index[0] == 0 | index[1] == 2:
            self.has_pawn = True


b2 = Cell((1, 1), 5)
print(b2)

which gives the output:

pygame 2.0.1 (SDL 2.0.14, Python 3.9.1)
Hello from the pygame community. https://www.pygame.org/contribute.html
<rect(5, 0, 5, 5)>
[Finished in 0.6s]

I hope someone can help me to get the attribute top of the Cell object to change.

Answer 1

I don't see what the problem here is. Your self.top is 0, that is why y in self.rect value is 0 as well. In following loop,

# Setting coordinates
for i in range(3):
    if index[1] == i:
         self.x = i*self.side
    if index[0] == i:
         self.y == (2-i)*self.side

The value of i in the last iteration is 2 , which means in the last iteration this happens.

self.y == (2-2)*5 # 0*5 = 0

This results in self.y being set to 0, which in turn sets self.top to 0. So, it's not a surprise that you get the result you are getting.

If you do

super().__init__(pygame.Rect(10, 10, 10, 10))

The result printed is in fact <rect(10, 10, 10, 10)> , so you should focus on fixing the loop instead.

Answer 2

You can simplify your code. You don't need the loop at all. Cell is a subclass of pygame.Rect . Compute the coordinate of the call:

x = index[1] * self.side
y = (index[0]-2) * self.side

Use super() to delegate to the constructor of pygame.Rect :

super().__init__(x, y, self.side, self.side) 

However, I don't know where -2 comes from. You may want something like:

x = offsetx + index[1] * self.side
y = offsety + index[0] * self.side

---

Class Cell :

class Cell(pygame.Rect):
    def __init__(self, index, side):
        self.index = index
        self.side = side
        self.color = None       # Index is a tuple from (0, 0) to (2, 2)
        self.has_pawn = None

        x = index[1] * self.side
        y = (index[0]-2) * self.side
        super().__init__(x, y, self.side, self.side) 

        # Setting color
        sum = self.index[0] + self.index[1]
        if sum % 2 == 0:
            self.color = light
        if sum % 2 == 1:
            self.color = dark

        # Setting has_pawn
        if index[0] == 0 | index[1] == 2:
            self.has_pawn = True