How to properly apply OOP in the bouncing ball code

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How to properly apply OOP in the bouncing ball code

Tommy C
I'm trying to apply OOP in this bouncing ball code in order to have multiple balls bouncing around the screen. The objective of this code is to create a method called settings, which controls all the settings for the screen and the bouncing behaviour of multiple balls, under the class Ball. However, I keep on getting errors related to attributes (e.g., speed). I'm new to OOP in Python so your help will be much appreciated. Thanks in advance.


import pygame
import random
import sys

pygame.init()

class Ball:
    def __init__(self, X, Y):
        self.velocity = [1,1]
        self.ball_image = pygame.image.load ("ball.jpg")
        self.ball_boundary = self.ball_image.get_rect ()
        self.black = [0,0,0]
        self.width = 800
        self.height = 600
        self.num = 8
        self.X = random.randint(0, self.width)
        self.Y = random.randint(0, self.height)

    def settings(self):
        #X = random.randint(0, self.width)
        #Y = random.randint(0, self.height)
        clock = pygame.time.Clock()
        size = self.width, self.height
        screen = pygame.display.set_mode(size)
        ball_boundary = self.ball_image.get_rect()
        speed = self.velocity
        pic = self.ball_image
        pygame.display.set_caption("Balls")
        num_balls = self.num
        ball_list = []

        for i in range(num_balls):
           ball_list.append( Ball(random.randint(10, self.width-10),random.randint(10, self.height-10)) )

        while 1:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    sys.exit(0)

            screen.fill(self.black)
            for balls in ball_list:
                if balls.ball_boundary.left < 0 or balls.ball_boundary.right > self.width:
                    balls.speed[0] = -balls.speed[0]
                if balls.ball_boundary.top < 0 or balls.ball_boundary.bottom > self.height:
                    balls.speed[1] = -balls.speed[1]
                balls.ball_boundary = balls.ball_boundary.move (self.velocity)
                screen.blit (balls.ball_image, balls.ball_boundary)
            pygame.display.flip()

play = Ball(random.randint(0, 800), random.randint(0, 600))

play.settings()




Message File Name Line Position
Traceback
    <module> C:\....\Multiple_balls_TC.py 63
    settings C:\....\Multiple_balls_TC.py 56
AttributeError: Ball instance has no attribute 'speed'


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How to properly apply OOP in the bouncing ball code

Ian Kelly-2
On May 8, 2015 9:46 AM, "Tommy C" <tommyc168168 at gmail.com> wrote:
>
> I'm trying to apply OOP in this bouncing ball code in order to have
multiple balls bouncing around the screen. The objective of this code is to
create a method called settings, which controls all the settings for the
screen and the bouncing behaviour of multiple balls, under the class Ball.
However, I keep on getting errors related to attributes (e.g., speed). I'm
new to OOP in Python so your help will be much appreciated. Thanks in
advance.

As the error says, the attribute does not exist.

> class Ball:
>     def __init__(self, X, Y):
>         self.velocity = [1,1]

Here where you set it, you call it "velocity".

>         speed = self.velocity

Here you create a local variable called "speed", which you never use.

>                 if balls.ball_boundary.left < 0 or
balls.ball_boundary.right > self.width:
>                     balls.speed[0] = -balls.speed[0]

And here you look up an attribute of Ball called "speed", which doesn't
match the name you used in __init__.

This is a muddled design overall. Your Ball class represents the individual
balls bouncing around the screen. It should not also contain details about
window size and the logic for the event loop. Use a separate class for that.

Similarly, if the purpose of your settings method is to manage settings,
why does it also contain all the bouncing logic? These should probably be
separate methods.
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How to properly apply OOP in the bouncing ball code

mwilson
In reply to this post by Tommy C
On Fri, 08 May 2015 08:40:34 -0700, Tommy C wrote:

> I'm trying to apply OOP in this bouncing ball code in order to have
> multiple balls bouncing around the screen. The objective of this code is
> to create a method called settings, which controls all the settings for
> the screen and the bouncing behaviour of multiple balls, under the class
> Ball. However, I keep on getting errors related to attributes (e.g.,
> speed). I'm new to OOP in Python so your help will be much appreciated.
> Thanks in advance.

I did something similar, with little characters running around the screen
under joystick control.  What I think:

1. Each instance of the Ball class should control the behaviour of one
ball.
2. The screen settings and global environment generally should be global,
not stuffed inside the behaviour of a Ball.
3. Keeping the list of Ball instances should be something the main
section of your program does, not stuffed inside the behaviour of a Ball.

Each of my little GamePlayer objects is subclassed from
pygame.sprite.Sprite .  I forget what I got by doing this (it's old code)
but looking up the docs for that class might give you some insights.  
Each GamePlayer object has an "update" method which accepts info from the
joystick and updates the player's movements, and a "draw" method which
the main loop calls on displaying every frame, to show the player's new
position and attitude.

You might be able to do something along these lines.

        Mel.


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How to properly apply OOP in the bouncing ball code

Tommy C
In reply to this post by Tommy C
Thanks for your help.

I have updated the code as follows, there are no more errors but the images will not move at all, as all the images are staying at the upper left corner. Please advice, thanks.


import sys, pygame

pygame.init()

size   = width,  height = 800, 600
black  = [0,0,0]
screen = pygame.display.set_mode(size)

class BALL:
    def __init__(self,image):
        self.ball     = pygame.image.load(image)
        self.ballrect = self.ball.get_rect()
        self.speed    = [2, 2]

    def control(self):
        ballmove = self.ballrect.move(self.speed)

        if ballmove.left < 0 or ballmove.right > width:
            self.speed[0] = -self.speed[0]

        if ballmove.top < 0  or ballmove.bottom > height:
            self.speed[1] = -self.speed[1]

    def settings(self):
        clock  = pygame.time.Clock()
        screen.fill(black)
        screen.blit(self.ball, self.ballrect)
        pygame.display.flip()
        clock.tick(60)
        while 1:
            for event in pygame.event.get():
                if event.type == pygame.QUIT: sys.exit()


bob = BALL("spongebob.png")
bob.control()
bob.settings()

patrick = BALL("patrick.jpg")
patrick.speed[0] = 5
patrick.speed[1] = 8
patrick.control()
patrick.settings()

jaws = BALL("jaws.jpg")
jaws.speed[0] = 1
jaws.speed[1] = 10
jaws.control()
jaws.settings()


On Friday, May 8, 2015 at 11:40:46 AM UTC-4, Tommy C wrote:

> I'm trying to apply OOP in this bouncing ball code in order to have multiple balls bouncing around the screen. The objective of this code is to create a method called settings, which controls all the settings for the screen and the bouncing behaviour of multiple balls, under the class Ball. However, I keep on getting errors related to attributes (e.g., speed). I'm new to OOP in Python so your help will be much appreciated. Thanks in advance.
>
>
> import pygame
> import random
> import sys
>
> pygame.init()
>
> class Ball:
>     def __init__(self, X, Y):
>         self.velocity = [1,1]
>         self.ball_image = pygame.image.load ("ball.jpg")
>         self.ball_boundary = self.ball_image.get_rect ()
>         self.black = [0,0,0]
>         self.width = 800
>         self.height = 600
>         self.num = 8
>         self.X = random.randint(0, self.width)
>         self.Y = random.randint(0, self.height)
>
>     def settings(self):
>         #X = random.randint(0, self.width)
>         #Y = random.randint(0, self.height)
>         clock = pygame.time.Clock()
>         size = self.width, self.height
>         screen = pygame.display.set_mode(size)
>         ball_boundary = self.ball_image.get_rect()
>         speed = self.velocity
>         pic = self.ball_image
>         pygame.display.set_caption("Balls")
>         num_balls = self.num
>         ball_list = []
>
>         for i in range(num_balls):
>            ball_list.append( Ball(random.randint(10, self.width-10),random.randint(10, self.height-10)) )
>
>         while 1:
>             for event in pygame.event.get():
>                 if event.type == pygame.QUIT:
>                     sys.exit(0)
>
>             screen.fill(self.black)
>             for balls in ball_list:
>                 if balls.ball_boundary.left < 0 or balls.ball_boundary.right > self.width:
>                     balls.speed[0] = -balls.speed[0]
>                 if balls.ball_boundary.top < 0 or balls.ball_boundary.bottom > self.height:
>                     balls.speed[1] = -balls.speed[1]
>                 balls.ball_boundary = balls.ball_boundary.move (self.velocity)
>                 screen.blit (balls.ball_image, balls.ball_boundary)
>             pygame.display.flip()
>
> play = Ball(random.randint(0, 800), random.randint(0, 600))
>
> play.settings()
>
>
>
>
> Message File Name Line Position
> Traceback
>     <module> C:\....\Multiple_balls_TC.py 63
>     settings C:\....\Multiple_balls_TC.py 56
> AttributeError: Ball instance has no attribute 'speed'



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How to properly apply OOP in the bouncing ball code

zipher
In reply to this post by Tommy C
On Friday, May 8, 2015 at 10:40:46 AM UTC-5, Tommy C wrote:
> I'm trying to apply OOP in this bouncing ball code in order to have multiple balls bouncing around the screen. The objective of this code is to create a method called settings, which controls all the settings for the screen and the bouncing behaviour of multiple balls, under the class Ball. However, I keep on getting errors related to attributes (e.g., speed). I'm new to OOP in Python so your help will be much appreciated. Thanks in advance.

You are making a error that few in the programming community have caught up to.  OOP design for *data abstraction* is a completely different beast that OOP for *simulation*.  The confusion is around the use of the word "object" which both denotes a physical world item and a virtual one detached from reality.

I would say that Python might not be the right fit, but instead a language dedicated to simulation.

Mark


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How to properly apply OOP in the bouncing ball code

zipher
On Monday, May 11, 2015 at 7:25:09 PM UTC-5, Dennis Lee Bieber wrote:
> On Mon, 11 May 2015 08:33:56 -0700 (PDT), zipher
> <dreamingforward at gmail.com> declaimed the following:
> >You are making a error that few in the programming community have caught up to.  OOP design for *data abstraction* is a completely different beast that OOP for *simulation*.  The confusion is around the use of the word "object" which both denotes a physical world item and a virtual one detached from reality.
> >
> >I would say that Python might not be the right fit, but instead a language dedicated to simulation.
>
> The danger there is that a "language dedicated to simulation" might
> mean "discrete event" simulation -- which would be an even worse fit to a
> problem of particle motion simulation.

Huh?  VPython successfully models particle motion simulation with discrete events.  I don't see how you're going to update a variable non-discretely.  Tensors?  Good luck.

Mark


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How to properly apply OOP in the bouncing ball code

Terry Reedy
On 5/11/2015 8:42 PM, zipher wrote:

> On Monday, May 11, 2015 at 7:25:09 PM UTC-5, Dennis Lee Bieber wrote:
>> On Mon, 11 May 2015 08:33:56 -0700 (PDT), zipher
>> <dreamingforward at gmail.com> declaimed the following:
>>> You are making a error that few in the programming community have caught up to.  OOP design for *data abstraction* is a completely different beast that OOP for *simulation*.  The confusion is around the use of the word "object" which both denotes a physical world item and a virtual one detached from reality.
>>>
>>> I would say that Python might not be the right fit, but instead a language dedicated to simulation.
>>
>> The danger there is that a "language dedicated to simulation" might
>> mean "discrete event" simulation -- which would be an even worse fit to a
>> problem of particle motion simulation.
>
> Huh?  VPython successfully models particle motion simulation with discrete events.  I don't see how you're going to update a variable non-discretely.  Tensors?  Good luck.
>
> Mark
>


--
Terry Jan Reedy



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How to properly apply OOP in the bouncing ball code

Oscar Benjamin-2
In reply to this post by Tommy C
On 11 May 2015 at 16:22, Tommy C <tommyc168168 at gmail.com> wrote:

> Thanks for your help.
>
> I have updated the code as follows, there are no more errors but the images will not move at all, as all the images are staying at the upper left corner. Please advice, thanks.
>
>
> import sys, pygame
>
> pygame.init()
>
> size   = width,  height = 800, 600
> black  = [0,0,0]
> screen = pygame.display.set_mode(size)
>
> class BALL:
>     def __init__(self,image):
>         self.ball     = pygame.image.load(image)
>         self.ballrect = self.ball.get_rect()
>         self.speed    = [2, 2]
>
>     def control(self):
>         ballmove = self.ballrect.move(self.speed)
>
>         if ballmove.left < 0 or ballmove.right > width:
>             self.speed[0] = -self.speed[0]
>
>         if ballmove.top < 0  or ballmove.bottom > height:
>             self.speed[1] = -self.speed[1]

The function below should not be a method on a particular ball object
as it is the global event loop for pygame. This needs to be a top
level function that updates the animation for all balls.

>     def settings(self):
>         clock  = pygame.time.Clock()
>         screen.fill(black)
>         screen.blit(self.ball, self.ballrect)
>         pygame.display.flip()
>         clock.tick(60)
>         while 1:
>             for event in pygame.event.get():
>                 if event.type == pygame.QUIT: sys.exit()

In this loop you need to add code that will call the control() method
of each ball and then redraw the screen. At the moment you only draw
the objects once at the top of the settings() method. Then the loop
runs until you quit. So it should be something like:

# The functions below would make sense as methods of an "App" class.

def run():
    while 1:
        for event in pygame.event.get():
            if event.type = pygame.QUIT:
                sys.exit()
        update()
        draw()

def update():
    for ball in balls:
        ball.control()

def draw():
    screen.fill(black)
    for ball in balls:
        ball.draw()  # You need to add this method to BALL
    pygame.display.flip()

balls = [BALL("spongebob.png"), BALL("jaws.jpg")]

run()  # Actually runs the program's event loop.


--
Oscar


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How to properly apply OOP in the bouncing ball code

Gregory Ewing
In reply to this post by zipher
Terry Reedy wrote:
> On 5/11/2015 8:42 PM, zipher wrote:
>> Huh?  VPython successfully models particle motion simulation with
>> discrete events.

That's a discrete approximation to a continuous process.
The term "discrete event simulation" is usually used to
mean modelling a process that is inherently discrete,
e.g. sending data packets over a network.

--
Greg