WEBVTT 00:00.020 --> 00:05.930 All right, so now that we've learned all about inheritance, it's time to apply the theory to our snake 00:05.930 --> 00:06.380 game. 00:06.380 --> 00:10.070 And we're going to use it to detect collision with food. 00:10.280 --> 00:15.650 Our snake should be able to hit a piece of food, which is just going to be a blue circle. 00:15.650 --> 00:21.680 And every time it touches the food, the circle moves to a new random location on the screen. 00:22.160 --> 00:27.830 If we take a look at our code, you can see that the Main.py controls the entire game. 00:27.830 --> 00:32.810 It dictates how the screen should behave and how the snake behaves. 00:32.840 --> 00:39.680 Now, everything that's to do with the snake, its appearance and behavior is all captured inside a 00:39.680 --> 00:40.370 class. 00:40.370 --> 00:44.150 So everything snake related is inside the snake class. 00:44.150 --> 00:51.110 So what we want to be able to do is to create a new food.py file. 00:51.110 --> 00:55.520 And this foo.py is going to be its own class. 00:55.520 --> 01:02.310 And the food class is going to know how to render itself as a small circle on the screen, and then 01:02.310 --> 01:09.330 every time the snake touches the food, then that food is going to move to a new random location. 01:09.360 --> 01:13.530 So let's create the initializer for this food class. 01:13.650 --> 01:19.920 And one of the things that we're going to need to do is we're going to need to import turtle. 01:19.950 --> 01:24.150 So from the turtle module let's import the turtle class. 01:24.150 --> 01:31.020 And this piece of food that we're going to see on screen is going to be a turtle object. 01:31.050 --> 01:34.290 Instead of creating it as an attribute in this class. 01:34.290 --> 01:36.870 So self dot food equals turtle. 01:36.870 --> 01:37.770 Like this. 01:37.770 --> 01:45.000 What we want to be able to do is we actually want this class food to inherit from the turtle class. 01:45.000 --> 01:51.750 So that way this food class is going to have all of the capabilities of the turtle class, but it's 01:51.750 --> 01:57.750 also going to have some specific things that we're going to tell it how to do, so that it behaves like 01:57.750 --> 01:59.230 an actual piece of food. 01:59.230 --> 02:02.680 Here's a quick challenge from what you learned in the last lesson. 02:02.680 --> 02:07.720 Can you figure out how to make this food class inherit from the turtle class? 02:07.750 --> 02:09.760 Pause the video and give that a go. 02:12.700 --> 02:15.970 All right, so we mentioned that there's only two steps we need to do. 02:16.000 --> 02:22.270 First is after the name of the class, we add some parentheses and then put in the name of the class 02:22.270 --> 02:23.920 that we want to inherit from. 02:23.920 --> 02:26.260 So in this case it's the turtle class. 02:26.260 --> 02:34.060 And then the next thing we need to do is we need to call the turtles init method inside the food's init 02:34.060 --> 02:34.810 method. 02:34.810 --> 02:41.710 And you can see that as soon as you've added this inheritance here, this init starts giving us a warning. 02:41.740 --> 02:47.440 And when you click on it, you can see it says call to init of superclass is missed. 02:47.440 --> 02:49.960 So it actually knows what we need to do next. 02:49.960 --> 02:55.390 That means if we click on the light bulb, we can actually automatically just add in the Superclass's 02:55.390 --> 02:56.890 call this. 02:56.920 --> 03:00.080 Of course, you could just type it out and it's good for practice. 03:00.080 --> 03:05.900 But in case you're ever wondering if you get these warnings, you can always take a look at what PyCharm 03:05.900 --> 03:07.130 is recommending. 03:07.340 --> 03:13.400 Now we've actually created our food class and we've inherited from the turtle class. 03:13.400 --> 03:18.860 What that means is we can now start using things that are from the turtle class. 03:19.130 --> 03:24.560 For example, I can straight up say self dot shape and it knows what shape is. 03:24.590 --> 03:30.260 This is a method that the turtle class has that I'm now going to modify in my food class. 03:30.260 --> 03:36.380 So when I initialize a new piece of food, I'm going to make sure that it has a circular shape. 03:36.410 --> 03:41.030 And I'm also going to get it to pen up so that it doesn't draw. 03:41.060 --> 03:44.180 And then I'm going to define its size. 03:44.180 --> 03:47.450 And there's something called shape size which I can use. 03:47.480 --> 03:54.050 And what this allows me to do is to stretch the turtle along its length and along its width. 03:54.080 --> 03:56.940 Now I'm not actually going to stretch it bigger than it is. 03:56.970 --> 04:03.060 It's normally 20 by 20 pixels, but I want to turn it into ten by ten pixels. 04:03.060 --> 04:06.120 So I'm going to stretch the length by 0.5. 04:06.120 --> 04:07.950 So I'm basically going to halve it. 04:07.950 --> 04:11.430 And then I'm going to stretch the width also by 0.5. 04:11.460 --> 04:18.750 So now it should be a ten by ten circle which I've created by defining the shape size. 04:18.780 --> 04:24.570 Now remember all of these methods shape size pin up shape comes from this turtle superclass. 04:24.570 --> 04:29.580 And we're only able to use it because we're inheriting from the superclass. 04:29.580 --> 04:36.690 So that our food class is now also sort of a turtle, but it's more like a souped up turtle. 04:36.990 --> 04:41.820 Finally, let's go ahead and define the color, which I'm going to set as blue. 04:41.820 --> 04:44.790 But of course, feel free to set it as anything you like. 04:44.820 --> 04:50.460 And I'm also going to set the speed of my turtle to a fastest. 04:50.460 --> 04:56.230 This way I don't have to look at the animation of the food being created at the center of the screen 04:56.230 --> 04:59.230 and then moving to the location that I want it to. 04:59.440 --> 05:06.910 Speaking of moving, we're going to need to use the go to to get it to go to a random XY location. 05:06.910 --> 05:16.360 So let's import the random module and let's create a random x which is going to be random.randint. 05:17.050 --> 05:20.290 Remember that our screen is 600 by 600. 05:20.290 --> 05:24.850 So that means that our x axis goes from -300 to positive 300. 05:24.850 --> 05:29.680 And our y axis goes from positive 300 to -300. 05:29.710 --> 05:34.930 Now we don't want our food to be right at the edge of the screen, because it will be really hard to 05:34.930 --> 05:37.420 get the snake to go to right at the edge. 05:37.420 --> 05:39.580 It'll probably just die on the wall. 05:39.580 --> 05:46.630 So we want to maybe subtract this a little bit so we can go from -280 to plus 280 and the same on the 05:46.630 --> 05:47.680 y axis. 05:47.680 --> 05:53.950 So let's generate a random integer from -280 to positive 280. 05:53.960 --> 05:59.480 and let's generate a random y integer in the same range. 05:59.480 --> 06:05.840 So now we can tell our food to go to a random x and a random y. 06:05.870 --> 06:12.620 All of this is going to happen as soon as we create a new food object from the food class. 06:12.620 --> 06:20.390 Remember, whenever you initialize a new object from the class, the init gets called back in our Main.py 06:20.420 --> 06:23.180 right below where we initialized our snake. 06:23.180 --> 06:25.280 We're going to initialize our food. 06:25.280 --> 06:29.960 So food equals the food class and then parentheses. 06:29.960 --> 06:37.760 And of course we need to get hold of our food class from the food file like this. 06:38.000 --> 06:43.880 Another thing you'll notice is that this turtle is now grayed out, because we're not using that class 06:43.880 --> 06:45.950 anywhere inside the main.py. 06:45.980 --> 06:49.850 So we can delete that, which gets rid of all our warnings on this page. 06:49.850 --> 06:51.890 And we get the green check mark. 06:52.070 --> 06:54.200 Our food up high looks good. 06:54.230 --> 06:56.450 Our snake up high looks good. 06:56.450 --> 07:00.320 And we're now ready to go ahead and run this code. 07:00.470 --> 07:04.790 Notice how we've got our snake moving around on screen. 07:04.790 --> 07:10.400 And at this point it doesn't really matter about the walls, it's just moving around anywhere it likes. 07:10.400 --> 07:16.880 But more importantly, we've got our food being randomly generated on the screen right here. 07:16.970 --> 07:24.620 Now the next step is how can we detect when the snake and the food have come into contact, and then 07:24.620 --> 07:29.000 to tell the food to move itself to a new random location? 07:29.030 --> 07:36.200 Well, we're going to do that inside our main.py right after we've got our screen updating, our snake 07:36.200 --> 07:36.890 moving. 07:36.890 --> 07:42.620 Then we're going to detect collision with food. 07:42.650 --> 07:48.560 And we're going to do that by using a method from the turtle class called distance. 07:48.770 --> 07:56.010 The distance method works by comparing the distance from this turtle to whatever it is that you put 07:56.010 --> 07:58.050 inside the parentheses. 07:58.050 --> 08:06.270 So the x could be a pair of numbers x and y, or it could simply just be a turtle instance. 08:06.270 --> 08:10.170 So you're comparing this turtle against another turtle. 08:10.170 --> 08:13.830 And you're trying to get hold of the distance between the two turtles. 08:13.860 --> 08:21.780 So what that means is we can check to see if the distance from the first segment of the snake. 08:21.780 --> 08:27.210 So remember that would be snakehead dot distance. 08:27.750 --> 08:34.470 And then the distance that we want to know is what is the distance from the snake's head to the food. 08:34.740 --> 08:39.360 At this point you can check to see if it is less than a certain amount. 08:39.360 --> 08:44.940 Then it's pretty likely that the snake head is now colliding with the food. 08:44.940 --> 08:48.300 So we know that the food is ten by ten. 08:48.300 --> 08:55.600 So if we add a bit of a buffer, Let's just say if the snakehead is within 15 pixels of the food, or 08:55.600 --> 08:56.830 even closer. 08:56.830 --> 09:02.890 So if the distance is less than 15, then we can be pretty much certain that they've collided. 09:02.890 --> 09:05.170 So let's go ahead and print something. 09:05.290 --> 09:06.400 I'll just write nom. 09:06.430 --> 09:07.150 Nom nom. 09:07.150 --> 09:15.490 So if we go ahead and run our code and let's just get our snake back into view, and if I now go and 09:15.490 --> 09:20.470 touch this piece of food, if I can, then you can see. 09:20.500 --> 09:23.020 Nom nom nom being printed in the console. 09:23.050 --> 09:25.090 Now let's go ahead and touch it again. 09:25.090 --> 09:32.110 You can see as soon as I collide with that food I get that print statement executing. 09:33.310 --> 09:39.190 So now instead of just writing nom nom nom, let's figure out what we need to do next. 09:39.190 --> 09:45.100 What we want to happen is the food should go to a new random location. 09:45.100 --> 09:48.910 And of course that comes from this part of the code. 09:48.910 --> 09:54.500 So why don't we go ahead and create a new method which will call refresh. 09:54.530 --> 10:02.660 And this refresh method is going to create a new random x, a new random y, and then get the food to 10:02.690 --> 10:05.300 go to that new random location. 10:05.360 --> 10:10.970 Then inside our init we can simply just call self dot refresh. 10:11.090 --> 10:16.550 So be careful that you didn't write reset, because that's one of the methods from the turtle class 10:16.550 --> 10:17.960 that we're inheriting from. 10:17.960 --> 10:24.740 But what we actually want is to call this refresh method so that the food goes to a new random location, 10:24.740 --> 10:31.790 and then back inside our main.py when the snake head collides with the food, then we're going to get 10:31.790 --> 10:35.330 the food to refresh its own location. 10:35.330 --> 10:36.770 So check this out. 10:36.800 --> 10:48.300 Now when I hit the food, then you can see the food now appears at a new random location like that. 10:48.330 --> 10:55.470 Now, depending on how accurate you want the snake to hit the food, so it might need to hit it dead 10:55.470 --> 10:55.920 on. 10:55.920 --> 11:02.880 Or if you're happy with it just gliding past and counting that as a collision, then you could decrease 11:02.880 --> 11:06.270 the number here from 15 to 10. 11:06.300 --> 11:12.540 Now I've done a bit of testing, and this number seems to be the best distance in order to get a valid 11:12.540 --> 11:13.320 collision. 11:13.320 --> 11:17.250 But feel free to tweak around with the number and see how it goes. 11:17.280 --> 11:18.000 There we go. 11:18.030 --> 11:23.010 We've managed to figure out how to create a piece of food by inheriting from the turtle class. 11:23.040 --> 11:30.930 Get the food to be generated, and then to move to a new random location every time the snake head collides 11:30.930 --> 11:31.800 with the food. 11:32.100 --> 11:39.000 Now, I know that in the snake game, the snake segments increase once it hits a piece of food, but 11:39.000 --> 11:44.970 we're only going to add that functionality at the very end of this project when we're detecting collision 11:44.970 --> 11:47.940 with the snake tail, so don't worry about that for now.