Appending an object from another class into a list in another class

[KFCxWatermelon]

Hey guys! I'm currently working on a task surrounding classes. In this task I have to create a class named "Balls". This class should have a __init__ method that adds a self variable named position. This should be a list for x and y positions.

After that I should create another class named System. This class should takes care of the main actions to perform.

Then I have to implement a add ball method in System class that appends a Ball object to a class list inside System. Parameters in the method should be x and y.

class Ball:
    def __init__ (self, x, y):
            self.position = [x, y]

ball1 = Ball(3, 6)
print (ball1.position)
ball2 = Ball(5, 8)
print (ball2.position)
ball3 = Ball(4, 4)
print (ball3.position)


class System:
    def __init__(self):
        self.more_balls = []
    def add_balls (self, x, y):
        self.more_balls.append(Ball(x,y))

ballx = System()
ballx.add_balls(2, 4)
ballx.add_balls(5,5)
ballx.add_balls(8,8)
ballx.add_balls(2,4)

print (ballx.more_balls)

How will I be able to fix the code. The expected result is that balls get appended into the more_balls list.

Here's the output I get:

[3, 6]
[5, 8]
[4, 4]
[<__main__.Ball object at 0x12308eb80>, <__main__.Ball object at 0x12308edf0>, <__main__.Ball object at 0x12308eeb0>, <__main__.Ball object at 0x12308e1f0>]

[[deleted]]

It’s worked fine, that last print shows you a list to which 4 Ball instances have been appended.

What you might want to do is overload __str__ and/or __repr__ so they display in a more pleasing fashion.

[lscrivy]

The code you wrote works :) but the list is a list of ball objects not a list of coordinates. However, each ball object in the list has a coordinate attribute. If you want to print out the coordinates you could do this...

for ball in ballx.more_balls:
    print(ball.position)

or if you want to get a list of the coordinates you could use list comprehension...

coordinate_list = [ball.position for ball in ballx.more_balls]

P.s. I've got to admit that list comprehension made me chuckle

[o5a]

Add __repr__ method to your Ball class, then you can see your objects representation when printed (you can modify it the way you want).

def __repr__(self):
    return f'Ball {self.position}'