WEBVTT 0 00:00.660 --> 00:05.070 In the last lesson we created and managed to move a paddle up and down. 1 00:05.670 --> 00:08.970 Now in this lesson, we're going to figure out how we can create 2 00:08.970 --> 00:09.930 another paddle, 3 00:10.260 --> 00:14.100 but we don't want to repeat all the code that we've written so far. 4 00:14.340 --> 00:18.900 So we're probably going to need the help of a separate paddle class. 5 00:19.320 --> 00:21.270 So if you haven't already created 6 00:21.270 --> 00:24.690 your paddle inside a separate file and a separate class, 7 00:25.050 --> 00:29.100 then this is the time to refactor your code so that you can create 8 00:29.100 --> 00:34.100 another paddle object from the puddle class easily and effortlessly. 9 00:34.830 --> 00:36.240 Here's what we're aiming for. 10 00:36.390 --> 00:41.390 We're aiming to get rid of all of this paddle related code and move it into a 11 00:41.640 --> 00:43.140 separate paddle class. 12 00:43.650 --> 00:48.650 And then subsequently we want to be able to create a right paddle simply by 13 00:50.250 --> 00:52.560 creating it from the paddle class. 14 00:52.950 --> 00:57.360 And then we can create a left paddle from the panel of class. Now because the 15 00:57.360 --> 01:01.380 right paddle has a different coordinate from the left paddle, 16 01:01.620 --> 01:06.620 we'll need to pass in the position of the right and left paddle as a tuple. 17 01:06.870 --> 01:11.870 So we might say something like the X will be 350 and the Y will be 0. 18 01:12.630 --> 01:13.980 And on the left paddle, 19 01:13.980 --> 01:18.980 the X will be -350 and the Y will be 0. 20 01:20.160 --> 01:25.160 So have a think about how you can make this code work and refactor this 21 01:26.250 --> 01:28.980 code into a separate paddle class 22 01:29.370 --> 01:33.330 and this paddle class should inherit from the turtle class. 23 01:33.780 --> 01:37.260 Overall, our program should work pretty much the same as before. 24 01:37.680 --> 01:41.010 The only difference being that we now have a left pedal 25 01:41.250 --> 01:45.510 which can move up and down with the w and s keys on the keyboard. 26 01:46.290 --> 01:48.810 Pause the video and try to complete this challenge. 27 01:51.450 --> 01:54.990 All right. So the first thing we're going to need is a new file, 28 01:55.260 --> 02:00.260 which is going to be called paddle.py and paddle.py is going to need the 29 02:01.410 --> 02:05.640 turtle class from the turtle module. So let's go ahead and import it. 30 02:06.180 --> 02:10.770 And then I'm going to create this Paddle class, and of course, 31 02:10.980 --> 02:13.590 all classes start off with a capital letter. 32 02:14.070 --> 02:19.070 Now, this class is going to take all of this paddle creation code 33 02:19.680 --> 02:23.550 and it's going to carry it out when we initialize a new paddle 34 02:23.550 --> 02:28.290 object. This paddle object, in order for it to be a turtle 35 02:28.290 --> 02:32.940 object, we're going to get it to inherit from the turtle class like this. 36 02:33.420 --> 02:35.880 And in order to get all of the abilities, 37 02:35.880 --> 02:38.610 the methods, and the attributes of the turtle class, 38 02:39.000 --> 02:41.940 we need to get this superclass to initialize itself. 39 02:42.660 --> 02:47.660 The next thing we're going to do is figure out how we can get our paddle to 40 02:47.910 --> 02:52.320 change its shape, change its color and all of these other things. 41 02:52.920 --> 02:57.920 So we can get rid of this line entirely because our paddle class is now the same 42 02:58.350 --> 03:01.870 as a turtle class. And then for the rest of these, 43 03:01.870 --> 03:04.960 instead of writing paddle.shape or paddle.color, 44 03:05.290 --> 03:09.460 we're going to hit command R or simply go to edit, 45 03:09.730 --> 03:12.280 find, and then replace, 46 03:12.460 --> 03:16.900 and you can take a look at the shortcut on your computer of how to get hold of 47 03:16.900 --> 03:20.380 this replace screen. So what I want to replace is 48 03:20.500 --> 03:23.890 everything that is paddled. here in my code, 49 03:24.280 --> 03:26.680 and I'm going to replace it with self., 50 03:27.190 --> 03:29.620 because now we're inside the paddle class 51 03:30.010 --> 03:34.360 which is effectively the same as a turtle class with some added extras. 52 03:34.750 --> 03:39.750 We can tap into our methods and our attributes by simply using the self keyword. 53 03:41.950 --> 03:42.760 Now, 54 03:42.760 --> 03:47.760 the very last thing we need to do in order to make this work is to go ahead and 55 03:48.700 --> 03:51.910 import our paddle from the paddle.py. 56 03:54.700 --> 03:58.540 And once we've imported it, we need to address this warning. 57 03:58.810 --> 04:00.670 Notice how it's highlighting this area 58 04:00.700 --> 04:05.700 and it's telling us that this is an unexpected argument because the paddle 59 04:05.830 --> 04:09.700 class doesn't actually take any inputs when it's initialized. 60 04:09.910 --> 04:12.760 It's just got the self here. But in fact, 61 04:12.790 --> 04:16.510 we do need a position being passed over. 62 04:17.020 --> 04:21.910 So this position is going to determine where the paddle is going to go to, 63 04:22.420 --> 04:26.950 because remember the left paddle is going to have a different coordinate from 64 04:26.950 --> 04:27.880 the right paddle. 65 04:28.540 --> 04:33.190 So now that we fixed that, this is now completely valid code. 66 04:35.590 --> 04:38.200 And if we run our code as it is, 67 04:38.260 --> 04:43.180 you'll see our paddles being created and looking exactly the same way as before 68 04:43.450 --> 04:48.450 but now we've got one extra paddle. Going down here with our go up and go down 69 04:50.140 --> 04:50.973 methods, 70 04:51.040 --> 04:55.360 ideally, we would want them to live within our paddle class. 71 04:55.690 --> 04:58.390 So we want them to be methods inside this class. 72 04:58.930 --> 05:03.930 And remember that methods always have a first attribute as the self. 73 05:05.050 --> 05:07.030 Now, in addition, we have to, again, 74 05:07.060 --> 05:12.060 replace this paddle. with self. so that it's actually referring to the object 75 05:14.410 --> 05:19.360 that's created from this class to get its Y coordinate or get its X coordinate. 76 05:20.080 --> 05:22.480 Now, coming back to our main.py, 77 05:22.510 --> 05:26.800 we'll have to modify this code a little bit because this go_up and go_down 78 05:26.800 --> 05:28.090 function is now gone, 79 05:28.450 --> 05:33.450 and instead, we now have the r_paddle.go_up and r_paddle.go_down. 80 05:36.970 --> 05:40.840 So the right paddle is going to be controlled by the up and down keys, 81 05:41.260 --> 05:46.210 but the left paddle, we can get it to be controlled by some other keys. Now, 82 05:46.210 --> 05:46.810 in our case, 83 05:46.810 --> 05:51.810 I'm going to choose the 'w' to go up and the 's' key to go down. 84 05:52.780 --> 05:57.780 So we're going to need another set of these screen.onkey method calls. 85 05:58.340 --> 05:59.180 But in this case, 86 05:59.180 --> 06:04.180 this is going to get the left paddle to go up and the left paddle to go down. And 87 06:05.000 --> 06:07.460 to go up is controlled by the 'w' key 88 06:07.730 --> 06:12.560 and to go down is controlled by the 's' key. So now, 89 06:12.590 --> 06:17.210 if we run our code, you can see that when I moved w it goes up, when I move 90 06:17.210 --> 06:21.950 s it goes down, and up and down moves the right side of the paddle. 91 06:22.640 --> 06:23.690 So notice how 92 06:23.720 --> 06:28.720 now that we've refactored our paddle related code into a completely separate 93 06:29.090 --> 06:30.560 class, firstly, 94 06:30.650 --> 06:34.160 our main.py is now a lot simpler. 95 06:34.190 --> 06:37.730 It's clear of all of this paddle related code. 96 06:38.270 --> 06:41.720 And on top of that, if I wanted to create a third paddle 97 06:41.720 --> 06:45.260 let's say I wanted you to create a top paddle for some reason, 98 06:45.530 --> 06:50.530 then all I have to do is just call the paddle class and then pass in a tuple 99 06:51.200 --> 06:53.900 for the location of this paddle. 100 06:54.950 --> 06:59.810 So let's put it at, I dunno, 100 by 100. 101 07:00.380 --> 07:01.213 If I hit run, 102 07:01.220 --> 07:05.180 you can see there's a third random paddle and I didn't have to write 103 07:05.300 --> 07:10.300 any of this extra code or any of the related methods. We can create as many of 104 07:10.790 --> 07:15.410 these paddles as we want because we've now got this paddle class. 105 07:16.460 --> 07:17.960 So with these examples, 106 07:18.050 --> 07:22.370 I hope you're getting the sense of how important classes are and just how 107 07:22.370 --> 07:26.990 important they are when it comes to the development of a more complex project 108 07:27.230 --> 07:30.230 like this pong game. Now in the next lesson, 109 07:30.230 --> 07:34.190 we're going to continue building out our program and we're going to create our 110 07:34.200 --> 07:36.770 ball class and get the ball moving.