WEBVTT 0 00:00.300 --> 00:02.250 Now that we've created both paddles 1 00:02.310 --> 00:07.020 the next obvious step is to create the ball and get it to move. 2 00:07.500 --> 00:12.500 So this ball is going to be created as a separate ball class and the ball object 3 00:14.550 --> 00:19.350 that we're going to create from it will have a width of 20, height of 20, and it's 4 00:19.380 --> 00:23.310 X and Y position will start out at the center of the screen, 5 00:23.490 --> 00:27.300 so (0, 0). Now when the screen refreshes, 6 00:27.300 --> 00:32.300 the ball is automatically going to move on the screen and it's going to move up 7 00:33.390 --> 00:34.920 and also to the right. 8 00:34.920 --> 00:39.920 So it's X and Y positions will change on every refresh of the screen. 9 00:40.800 --> 00:45.000 So this is going to be a little bit more challenging and will require a little 10 00:45.000 --> 00:46.320 bit of thinking from your part. 11 00:46.680 --> 00:51.390 But I want you to pause the video and give this problem a bit of thought and see 12 00:51.390 --> 00:55.590 how far you can get in trying to get the ball to move to the top- 13 00:55.620 --> 00:59.580 right edge of the screen. Pause the video and give that a go. 14 01:03.260 --> 01:05.330 All right. So to start off, this time 15 01:05.330 --> 01:10.250 I'm going to create a ball.py file and inside 16 01:10.280 --> 01:14.330 this ball.py is where we're going to create our ball object. 17 01:14.750 --> 01:15.830 So firstly, 18 01:15.830 --> 01:20.830 I'm going to import my turtle class and then I'm going to create my ball class 19 01:22.040 --> 01:24.320 which is going to inherit from the turtle class. 20 01:24.800 --> 01:28.130 And then I'm going to do all of the usual initialization. 21 01:30.440 --> 01:33.950 And now we're ready to create our ball class. 22 01:34.430 --> 01:39.080 This ball is going to, firstly, have a white color. 23 01:39.710 --> 01:44.300 And in addition, it's going to have a shape that is going to be a circle. 24 01:44.600 --> 01:47.510 Now I know that in the original pong game, 25 01:47.600 --> 01:52.250 the table tennis ball is actually a square. So you can keep it a square 26 01:52.250 --> 01:56.300 if you want to be historically accurate, or you can change it to 27 01:56.300 --> 02:00.650 a circle like I have here to make it look more like a ping pong ball. 28 02:01.370 --> 02:02.360 Now, in addition, 29 02:02.390 --> 02:06.980 we're going to need to get it to pen up so that it doesn't end up drawing across 30 02:06.980 --> 02:07.813 the screen. 31 02:08.210 --> 02:13.210 And now all we need is to initialize our ball from the ball.py 32 02:17.870 --> 02:20.600 and we're going to do that just below our paddles. 33 02:20.660 --> 02:24.500 So I'm going to create a new ball object from the ball class. 34 02:25.010 --> 02:26.390 And now if I hit run, 35 02:26.420 --> 02:30.380 you'll see our circular ball show up in the center of the screen. 36 02:31.430 --> 02:36.430 The next problem is how do we get the ball to move towards the top right corner 37 02:37.310 --> 02:38.143 of the screen? 38 02:38.360 --> 02:42.500 So that's going to involve a change in the X coordinate as well as the Y 39 02:42.500 --> 02:45.590 coordinate. In our while loop here 40 02:45.740 --> 02:47.720 where our screen is updating, 41 02:48.050 --> 02:51.410 we're going to call a method in the ball class 42 02:51.710 --> 02:56.000 which is going to be called move. And this move method 43 02:56.030 --> 03:01.030 which we'll define now is going to be responsible for moving our ball. 44 03:02.290 --> 03:07.290 And the way that it's going to move is it's going to increase on the X and also 45 03:08.350 --> 03:12.790 increase on the Y. Let's create a new X coordinate 46 03:12.820 --> 03:17.820 which is going to be the current self.xcor plus a arbitrary amount. 47 03:18.850 --> 03:20.770 So let's say increase by 10. 48 03:21.220 --> 03:26.220 And then the new Y is going to be the self.ycor increased by the same 49 03:27.730 --> 03:30.160 arbitrary amount. And then finally, 50 03:30.190 --> 03:35.190 we can get our ball to go to this new X and new Y. 51 03:37.690 --> 03:39.640 So now when we run our code, 52 03:39.880 --> 03:44.500 you can see that our ball immediately goes off the screen to the top right 53 03:44.500 --> 03:48.130 corner. If we want the ball to slow down a little bit, 54 03:48.190 --> 03:50.950 we can do one of two things. Either 55 03:50.980 --> 03:55.980 we can go into the move method and change this 10 here to say a 1. 56 03:57.010 --> 04:01.360 That way, every time our loop runs, our ball will only move one pixel. 57 04:02.080 --> 04:06.490 Alternatively, we can pause the loop for a short time during each iteration. 58 04:07.480 --> 04:10.180 Moving the ball at a tiny amount does work, 59 04:10.330 --> 04:14.350 but I'm going to go with the second option and import our time module. 60 04:14.770 --> 04:18.790 Then I'm going to get our while loop to sleep for a little bit in between each 61 04:18.790 --> 04:19.690 of the updates. 62 04:20.320 --> 04:24.460 So, I normally start off with just a 0.1 second sleep, 63 04:24.790 --> 04:28.450 and you can see now a ball moves at a more reasonable pace 64 04:28.720 --> 04:31.690 and we actually have a chance of catching it with one of the paddles. 65 04:32.530 --> 04:37.210 That's all there is to it. We've now created on the ball class, initialized 66 04:37.270 --> 04:42.270 a ball object and we've got the ball to move on every refresh of the screen.