1 00:00:00,660 --> 00:00:05,070 In the last lesson we created and managed to move a paddle up and down. 2 00:00:05,670 --> 00:00:08,970 Now in this lesson, we're going to figure out how we can create 3 00:00:08,970 --> 00:00:09,930 another paddle, 4 00:00:10,260 --> 00:00:14,100 but we don't want to repeat all the code that we've written so far. 5 00:00:14,340 --> 00:00:18,900 So we're probably going to need the help of a separate paddle class. 6 00:00:19,320 --> 00:00:21,270 So if you haven't already created 7 00:00:21,270 --> 00:00:24,690 your paddle inside a separate file and a separate class, 8 00:00:25,050 --> 00:00:29,100 then this is the time to refactor your code so that you can create 9 00:00:29,100 --> 00:00:34,100 another paddle object from the puddle class easily and effortlessly. 10 00:00:34,830 --> 00:00:36,240 Here's what we're aiming for. 11 00:00:36,390 --> 00:00:41,390 We're aiming to get rid of all of this paddle related code and move it into a 12 00:00:41,640 --> 00:00:43,140 separate paddle class. 13 00:00:43,650 --> 00:00:48,650 And then subsequently we want to be able to create a right paddle simply by 14 00:00:50,250 --> 00:00:52,560 creating it from the paddle class. 15 00:00:52,950 --> 00:00:57,360 And then we can create a left paddle from the panel of class. Now because the 16 00:00:57,360 --> 00:01:01,380 right paddle has a different coordinate from the left paddle, 17 00:01:01,620 --> 00:01:06,620 we'll need to pass in the position of the right and left paddle as a tuple. 18 00:01:06,870 --> 00:01:11,870 So we might say something like the X will be 350 and the Y will be 0. 19 00:01:12,630 --> 00:01:13,980 And on the left paddle, 20 00:01:13,980 --> 00:01:18,980 the X will be -350 and the Y will be 0. 21 00:01:20,160 --> 00:01:25,160 So have a think about how you can make this code work and refactor this 22 00:01:26,250 --> 00:01:28,980 code into a separate paddle class 23 00:01:29,370 --> 00:01:33,330 and this paddle class should inherit from the turtle class. 24 00:01:33,780 --> 00:01:37,260 Overall, our program should work pretty much the same as before. 25 00:01:37,680 --> 00:01:41,010 The only difference being that we now have a left pedal 26 00:01:41,250 --> 00:01:45,510 which can move up and down with the w and s keys on the keyboard. 27 00:01:46,290 --> 00:01:48,810 Pause the video and try to complete this challenge. 28 00:01:51,450 --> 00:01:54,990 All right. So the first thing we're going to need is a new file, 29 00:01:55,260 --> 00:02:00,260 which is going to be called paddle.py and paddle.py is going to need the 30 00:02:01,410 --> 00:02:05,640 turtle class from the turtle module. So let's go ahead and import it. 31 00:02:06,180 --> 00:02:10,770 And then I'm going to create this Paddle class, and of course, 32 00:02:10,979 --> 00:02:13,590 all classes start off with a capital letter. 33 00:02:14,070 --> 00:02:19,070 Now, this class is going to take all of this paddle creation code 34 00:02:19,680 --> 00:02:23,550 and it's going to carry it out when we initialize a new paddle 35 00:02:23,550 --> 00:02:28,290 object. This paddle object, in order for it to be a turtle 36 00:02:28,290 --> 00:02:32,940 object, we're going to get it to inherit from the turtle class like this. 37 00:02:33,420 --> 00:02:35,880 And in order to get all of the abilities, 38 00:02:35,880 --> 00:02:38,610 the methods, and the attributes of the turtle class, 39 00:02:39,000 --> 00:02:41,940 we need to get this superclass to initialize itself. 40 00:02:42,660 --> 00:02:47,660 The next thing we're going to do is figure out how we can get our paddle to 41 00:02:47,910 --> 00:02:52,320 change its shape, change its color and all of these other things. 42 00:02:52,920 --> 00:02:57,920 So we can get rid of this line entirely because our paddle class is now the same 43 00:02:58,350 --> 00:03:01,870 as a turtle class. And then for the rest of these, 44 00:03:01,870 --> 00:03:04,960 instead of writing paddle.shape or paddle.color, 45 00:03:05,290 --> 00:03:09,460 we're going to hit command R or simply go to edit, 46 00:03:09,730 --> 00:03:12,280 find, and then replace, 47 00:03:12,460 --> 00:03:16,900 and you can take a look at the shortcut on your computer of how to get hold of 48 00:03:16,900 --> 00:03:20,380 this replace screen. So what I want to replace is 49 00:03:20,500 --> 00:03:23,890 everything that is paddled. here in my code, 50 00:03:24,280 --> 00:03:26,680 and I'm going to replace it with self., 51 00:03:27,190 --> 00:03:29,620 because now we're inside the paddle class 52 00:03:30,010 --> 00:03:34,360 which is effectively the same as a turtle class with some added extras. 53 00:03:34,750 --> 00:03:39,750 We can tap into our methods and our attributes by simply using the self keyword. 54 00:03:41,950 --> 00:03:42,760 Now, 55 00:03:42,760 --> 00:03:47,760 the very last thing we need to do in order to make this work is to go ahead and 56 00:03:48,700 --> 00:03:51,910 import our paddle from the paddle.py. 57 00:03:54,700 --> 00:03:58,540 And once we've imported it, we need to address this warning. 58 00:03:58,810 --> 00:04:00,670 Notice how it's highlighting this area 59 00:04:00,700 --> 00:04:05,700 and it's telling us that this is an unexpected argument because the paddle 60 00:04:05,830 --> 00:04:09,700 class doesn't actually take any inputs when it's initialized. 61 00:04:09,910 --> 00:04:12,760 It's just got the self here. But in fact, 62 00:04:12,790 --> 00:04:16,510 we do need a position being passed over. 63 00:04:17,019 --> 00:04:21,910 So this position is going to determine where the paddle is going to go to, 64 00:04:22,420 --> 00:04:26,950 because remember the left paddle is going to have a different coordinate from 65 00:04:26,950 --> 00:04:27,880 the right paddle. 66 00:04:28,540 --> 00:04:33,190 So now that we fixed that, this is now completely valid code. 67 00:04:35,590 --> 00:04:38,200 And if we run our code as it is, 68 00:04:38,260 --> 00:04:43,180 you'll see our paddles being created and looking exactly the same way as before 69 00:04:43,450 --> 00:04:48,450 but now we've got one extra paddle. Going down here with our go up and go down 70 00:04:50,140 --> 00:04:50,973 methods, 71 00:04:51,040 --> 00:04:55,360 ideally, we would want them to live within our paddle class. 72 00:04:55,690 --> 00:04:58,390 So we want them to be methods inside this class. 73 00:04:58,930 --> 00:05:03,930 And remember that methods always have a first attribute as the self. 74 00:05:05,050 --> 00:05:07,030 Now, in addition, we have to, again, 75 00:05:07,060 --> 00:05:12,060 replace this paddle. with self. so that it's actually referring to the object 76 00:05:14,410 --> 00:05:19,360 that's created from this class to get its Y coordinate or get its X coordinate. 77 00:05:20,080 --> 00:05:22,480 Now, coming back to our main.py, 78 00:05:22,510 --> 00:05:26,800 we'll have to modify this code a little bit because this go_up and go_down 79 00:05:26,800 --> 00:05:28,090 function is now gone, 80 00:05:28,450 --> 00:05:33,450 and instead, we now have the r_paddle.go_up and r_paddle.go_down. 81 00:05:36,970 --> 00:05:40,840 So the right paddle is going to be controlled by the up and down keys, 82 00:05:41,260 --> 00:05:46,210 but the left paddle, we can get it to be controlled by some other keys. Now, 83 00:05:46,210 --> 00:05:46,810 in our case, 84 00:05:46,810 --> 00:05:51,810 I'm going to choose the 'w' to go up and the 's' key to go down. 85 00:05:52,780 --> 00:05:57,780 So we're going to need another set of these screen.onkey method calls. 86 00:05:58,340 --> 00:05:59,180 But in this case, 87 00:05:59,180 --> 00:06:04,180 this is going to get the left paddle to go up and the left paddle to go down. And 88 00:06:05,000 --> 00:06:07,460 to go up is controlled by the 'w' key 89 00:06:07,730 --> 00:06:12,560 and to go down is controlled by the 's' key. So now, 90 00:06:12,590 --> 00:06:17,210 if we run our code, you can see that when I moved w it goes up, when I move 91 00:06:17,210 --> 00:06:21,950 s it goes down, and up and down moves the right side of the paddle. 92 00:06:22,640 --> 00:06:23,690 So notice how 93 00:06:23,720 --> 00:06:28,720 now that we've refactored our paddle related code into a completely separate 94 00:06:29,090 --> 00:06:30,560 class, firstly, 95 00:06:30,650 --> 00:06:34,160 our main.py is now a lot simpler. 96 00:06:34,190 --> 00:06:37,730 It's clear of all of this paddle related code. 97 00:06:38,270 --> 00:06:41,720 And on top of that, if I wanted to create a third paddle 98 00:06:41,720 --> 00:06:45,260 let's say I wanted you to create a top paddle for some reason, 99 00:06:45,530 --> 00:06:50,530 then all I have to do is just call the paddle class and then pass in a tuple 100 00:06:51,200 --> 00:06:53,900 for the location of this paddle. 101 00:06:54,950 --> 00:06:59,810 So let's put it at, I dunno, 100 by 100. 102 00:07:00,380 --> 00:07:01,213 If I hit run, 103 00:07:01,220 --> 00:07:05,180 you can see there's a third random paddle and I didn't have to write 104 00:07:05,300 --> 00:07:10,300 any of this extra code or any of the related methods. We can create as many of 105 00:07:10,790 --> 00:07:15,410 these paddles as we want because we've now got this paddle class. 106 00:07:16,460 --> 00:07:17,960 So with these examples, 107 00:07:18,050 --> 00:07:22,370 I hope you're getting the sense of how important classes are and just how 108 00:07:22,370 --> 00:07:26,990 important they are when it comes to the development of a more complex project 109 00:07:27,230 --> 00:07:30,230 like this pong game. Now in the next lesson, 110 00:07:30,230 --> 00:07:34,190 we're going to continue building out our program and we're going to create our 111 00:07:34,200 --> 00:07:36,770 ball class and get the ball moving.