1 00:00:05,560 --> 00:00:07,300 So in this video, we're gonna start 2 00:00:07,300 --> 00:00:09,340 talking about an object-orientated term 3 00:00:09,340 --> 00:00:12,110 called inheritance, or called inheritance, 4 00:00:12,110 --> 00:00:16,090 and specifically how that applies to Python programming. 5 00:00:16,090 --> 00:00:17,550 So I'm gonna start off by explaining 6 00:00:17,550 --> 00:00:18,970 what inheritance is, 7 00:00:18,970 --> 00:00:20,740 and then we'll move into some coding 8 00:00:20,740 --> 00:00:23,530 to go through some examples of inheritance, 9 00:00:23,530 --> 00:00:25,310 and inheritance in Python, 10 00:00:25,310 --> 00:00:26,930 and also gonna give you an overview 11 00:00:26,930 --> 00:00:29,580 of the benefits it can bring to your code. 12 00:00:29,580 --> 00:00:33,750 So let's swing over to a slide and go through that. 13 00:00:34,600 --> 00:00:36,080 Okay, so let's talk about 14 00:00:36,080 --> 00:00:39,490 a real world example of inheritance. 15 00:00:39,490 --> 00:00:42,020 Now, different types of objects in the real world 16 00:00:42,020 --> 00:00:46,530 can have a certain amount in common with each other. 17 00:00:46,530 --> 00:00:51,490 For example, a seagull, a crow, and an eagle are all birds, 18 00:00:51,490 --> 00:00:54,170 and so are ostriches and penguins. 19 00:00:54,170 --> 00:00:55,300 So in other words, they share 20 00:00:55,300 --> 00:00:57,960 their being-a-bird trait, so to speak. 21 00:00:57,960 --> 00:00:59,660 They all have a beak and wings, 22 00:00:59,660 --> 00:01:01,850 things that they inherit by virtue 23 00:01:01,850 --> 00:01:03,520 of them being birds. 24 00:01:06,060 --> 00:01:08,820 Another example is Monopoly, the board game, 25 00:01:08,820 --> 00:01:12,490 Blackjack the card game, and Halo the computer game. 26 00:01:12,490 --> 00:01:14,100 They're all inherently games, 27 00:01:14,100 --> 00:01:15,730 so again, they share that trait, 28 00:01:15,730 --> 00:01:17,740 the trait of being a game. 29 00:01:17,740 --> 00:01:19,770 But they're also different as well. 30 00:01:19,770 --> 00:01:21,940 Now, while they do share similarities, 31 00:01:21,940 --> 00:01:24,090 they are different in their own right. 32 00:01:24,090 --> 00:01:26,410 And as I mentioned, Monopoly is a board game, 33 00:01:26,410 --> 00:01:28,570 Blackjack is a card game, and of course, 34 00:01:28,570 --> 00:01:30,320 Halo is a video game. 35 00:01:32,120 --> 00:01:34,940 So the point here is that they share similar properties, 36 00:01:34,940 --> 00:01:36,660 being a game in this case, 37 00:01:36,660 --> 00:01:39,400 but also they've got differences as well. 38 00:01:39,400 --> 00:01:41,190 Now, for example, Halo, being a video game, 39 00:01:41,190 --> 00:01:42,770 as I mentioned, and it works 40 00:01:42,770 --> 00:01:45,290 on a video game console or a computer. 41 00:01:45,290 --> 00:01:47,320 Likewise, Blackjack is a card game, 42 00:01:47,320 --> 00:01:49,000 and Monopoly is a board game, 43 00:01:49,000 --> 00:01:51,400 but of course they can still work on a computer. 44 00:01:51,400 --> 00:01:56,390 There's a computer version of both of those games. 45 00:01:56,390 --> 00:01:59,460 Now, getting back to the birds example, 46 00:01:59,460 --> 00:02:01,540 now our birds do share a lot of traits. 47 00:02:01,540 --> 00:02:03,420 They all have feathers, for example, 48 00:02:03,420 --> 00:02:07,140 and that's one of the things that makes them birds. 49 00:02:07,140 --> 00:02:10,910 So what we can do is, we can define a base class 50 00:02:10,910 --> 00:02:13,030 that objects are based on in Python, 51 00:02:13,030 --> 00:02:14,270 things that are common for classes 52 00:02:14,270 --> 00:02:16,750 that derive from the base class. 53 00:02:16,750 --> 00:02:18,090 And then we can allow a class 54 00:02:18,090 --> 00:02:21,450 to define the unique characteristics of itself. 55 00:02:21,450 --> 00:02:23,660 So in other words, we have a base class, 56 00:02:23,660 --> 00:02:25,810 then something that inherits from that 57 00:02:25,810 --> 00:02:29,980 to make it something else again, making it unique. 58 00:02:31,710 --> 00:02:34,140 Now, the base class in this example here is bird. 59 00:02:34,140 --> 00:02:37,650 You can see, you can see the bird example in the image. 60 00:02:37,650 --> 00:02:41,780 And from that, all the birds inherit a beak and wings. 61 00:02:41,780 --> 00:02:43,260 But each type of bird also has things 62 00:02:43,260 --> 00:02:45,360 that make it different from the others. 63 00:02:45,360 --> 00:02:48,490 Now, eagles have incredibly good eyesight, for example. 64 00:02:48,490 --> 00:02:49,530 Now while you may be pleased 65 00:02:49,530 --> 00:02:52,210 if you spot a MacDonald's from 400 metres, 66 00:02:52,210 --> 00:02:54,670 eagles can literally see things two miles away. 67 00:02:54,670 --> 00:02:56,500 They can see a rabbit two miles away, 68 00:02:56,500 --> 00:02:58,500 which is pretty amazing. 69 00:03:00,510 --> 00:03:03,440 So all our birds inherit some base properties 70 00:03:03,440 --> 00:03:04,990 from their base class, 71 00:03:04,990 --> 00:03:08,120 which is often referred to as the superclass. 72 00:03:08,120 --> 00:03:09,970 Now they also inherit methods, 73 00:03:09,970 --> 00:03:12,240 so all our birds can walk and eat, 74 00:03:12,240 --> 00:03:14,720 but the individual bird classes also have 75 00:03:14,720 --> 00:03:17,760 their own unique properties and methods. 76 00:03:17,760 --> 00:03:19,800 So in this case, penguins can swim, 77 00:03:19,800 --> 00:03:22,720 and ostriches can run, for example. 78 00:03:24,660 --> 00:03:26,540 Now these individual bird classes 79 00:03:26,540 --> 00:03:29,100 are referred to as subclasses. 80 00:03:29,100 --> 00:03:31,430 So crow is a subclass of bird, 81 00:03:31,430 --> 00:03:34,620 which makes bird a superclass of crow. 82 00:03:34,620 --> 00:03:37,250 Now the idea of subclassing can be taken further, 83 00:03:37,250 --> 00:03:39,990 so we could add subclasses of bird, 84 00:03:39,990 --> 00:03:43,330 such as flying bird and flightless bird. 85 00:03:45,410 --> 00:03:47,910 Now, eagle is a subclass of flying bird, 86 00:03:47,910 --> 00:03:50,990 and ostrich is a subclass of flightless bird. 87 00:03:50,990 --> 00:03:53,980 In our example, eagles, crows, and gulls 88 00:03:53,980 --> 00:03:58,140 inherit the ability to fly from the flying bird superclass. 89 00:04:00,540 --> 00:04:03,020 Ostriches and penguins aren't inheriting anything 90 00:04:03,020 --> 00:04:06,200 from their flightless bird superclass in this example, 91 00:04:06,200 --> 00:04:08,420 but they still inherit their beaks and wings 92 00:04:08,420 --> 00:04:10,700 from the bird superclass. 93 00:04:10,700 --> 00:04:12,510 Now, ostriches have a run method, 94 00:04:12,510 --> 00:04:14,440 and penguins have a swim method, 95 00:04:14,440 --> 00:04:17,190 so a class can introduce other properties and methods 96 00:04:17,190 --> 00:04:20,600 in addition to the ones that it inherits. 97 00:04:22,590 --> 00:04:25,910 So a class can have more than one superclass in a hierarchy, 98 00:04:25,910 --> 00:04:27,420 like in this slide. 99 00:04:27,420 --> 00:04:29,930 Now in Python, classes can inherit directly 100 00:04:29,930 --> 00:04:31,720 from several superclasses, 101 00:04:31,720 --> 00:04:34,250 which is known as multiple inheritance. 102 00:04:34,250 --> 00:04:37,180 Now, many programming languages don't allow this, 103 00:04:37,180 --> 00:04:39,140 so the class structure ends up being 104 00:04:39,140 --> 00:04:43,320 strictly hierarchical, as I've shown here. 105 00:04:43,320 --> 00:04:44,840 Java classes, for example, 106 00:04:44,840 --> 00:04:46,690 can have more than one superclass, 107 00:04:46,690 --> 00:04:49,190 but it has to be hierarchical. 108 00:04:51,200 --> 00:04:53,890 Now, Python does allow multiple inheritance, 109 00:04:53,890 --> 00:04:56,050 but I strongly recommend you avoid it 110 00:04:56,050 --> 00:04:57,570 until you're really comfortable 111 00:04:57,570 --> 00:04:59,970 with classes and inheritance. 112 00:04:59,970 --> 00:05:01,130 And once you're really comfortable 113 00:05:01,130 --> 00:05:02,570 with classes and inheritance, 114 00:05:02,570 --> 00:05:05,640 I recommend you avoid multiple inheritance. (chuckles) 115 00:05:05,640 --> 00:05:07,410 Seriously, though, I do recommend you 116 00:05:07,410 --> 00:05:10,200 really look at avoiding multiple inheritance. 117 00:05:10,200 --> 00:05:13,300 Now the sphinx may have inherited the head of a human, 118 00:05:13,300 --> 00:05:16,680 the body of a lion, and the wings of a bird, 119 00:05:16,680 --> 00:05:19,670 but you don't see many sphinxes wandering around. 120 00:05:19,670 --> 00:05:22,370 So if nature's decided that multiple inheritance, 121 00:05:22,370 --> 00:05:25,120 is a bad idea, who am I to argue? 122 00:05:28,220 --> 00:05:30,310 Seriously though, having said that, 123 00:05:30,310 --> 00:05:34,010 multiple inheritance can be an extremely powerful tool 124 00:05:34,010 --> 00:05:36,780 when used correctly, but I'm not going to cover 125 00:05:36,780 --> 00:05:38,670 multiple inheritance in this course, 126 00:05:38,670 --> 00:05:41,370 but what I will do is mention it now and then 127 00:05:41,370 --> 00:05:44,010 to point out places where you could really 128 00:05:44,010 --> 00:05:45,340 hit some of the pitfalls, 129 00:05:45,340 --> 00:05:47,560 if you decided to use multiple inheritance 130 00:05:47,560 --> 00:05:51,730 or a multiple inheritance relationship in the future. 131 00:05:54,020 --> 00:05:56,730 So coming back to our examples here, 132 00:05:56,730 --> 00:05:59,370 flying bird is a subclass of bird, 133 00:05:59,370 --> 00:06:02,380 and eagle is a subclass of flying bird. 134 00:06:02,380 --> 00:06:04,830 Now eagle is also a subclass of bird, 135 00:06:04,830 --> 00:06:08,020 because its immediate superclass, flying bird, 136 00:06:08,020 --> 00:06:10,030 is a subclass of bird. 137 00:06:10,030 --> 00:06:12,470 So just to labour the point one more time, 138 00:06:12,470 --> 00:06:15,740 flying bird is a superclass of the three classes 139 00:06:15,740 --> 00:06:19,910 eagle, crow, and gull, and it's also a subclass of bird. 140 00:06:23,530 --> 00:06:25,320 So you might be asking at this point, 141 00:06:25,320 --> 00:06:26,500 "Tim, why should I bother to go 142 00:06:26,500 --> 00:06:28,770 "through all this level of complexity?" 143 00:06:28,770 --> 00:06:30,770 Well, in answer to that, firstly, 144 00:06:30,770 --> 00:06:32,760 it allows you to write code once, 145 00:06:32,760 --> 00:06:35,050 and then for that code to be used automatically 146 00:06:35,050 --> 00:06:36,590 by other classes. 147 00:06:36,590 --> 00:06:38,590 Now, if we created an eagle object, 148 00:06:38,590 --> 00:06:41,200 it would automatically get beak and wing, 149 00:06:41,200 --> 00:06:42,650 and wings properties, 150 00:06:42,650 --> 00:06:45,100 together with any methods that we'd created, 151 00:06:45,100 --> 00:06:47,660 or we had created, in the bird class, 152 00:06:47,660 --> 00:06:49,260 and that's without us having to write 153 00:06:49,260 --> 00:06:51,600 any code in the eagle class. 154 00:06:54,300 --> 00:06:55,450 So this leave you to define 155 00:06:55,450 --> 00:06:58,000 the unique characteristics of a class, 156 00:06:58,000 --> 00:07:00,000 rather than having to reinvent the wheel 157 00:07:00,000 --> 00:07:02,580 each time you create a new class. 158 00:07:02,580 --> 00:07:04,740 So in other words, you can write that code once, 159 00:07:04,740 --> 00:07:06,830 put that code in the super class, 160 00:07:06,830 --> 00:07:11,590 and then any class that extends or inherits from that class, 161 00:07:11,590 --> 00:07:13,270 they're the same thing effectively, 162 00:07:13,270 --> 00:07:15,180 is going to be able to take advantage 163 00:07:15,180 --> 00:07:16,850 of the properties or methods 164 00:07:16,850 --> 00:07:19,390 that are defined in the superclass. 165 00:07:19,390 --> 00:07:21,530 All right, so that's our overview of inheritance. 166 00:07:21,530 --> 00:07:23,420 Let's go back to the code 167 00:07:23,420 --> 00:07:27,590 and start working at an example in our game project. 168 00:07:29,690 --> 00:07:32,060 All right, so we're gonna continue with the game project 169 00:07:32,060 --> 00:07:33,730 that we created in the previous video, 170 00:07:33,730 --> 00:07:35,470 just to make sure that, 171 00:07:35,470 --> 00:07:37,560 so make sure you've got that class, 172 00:07:37,560 --> 00:07:39,140 that project open. 173 00:07:39,140 --> 00:07:41,610 Now, we're going to open the project pane, 174 00:07:41,610 --> 00:07:45,080 and we're going to create a superclass called enemy. 175 00:07:45,080 --> 00:07:46,730 And this'll be the base class 176 00:07:46,730 --> 00:07:49,280 for all the things our players will have to fight 177 00:07:49,280 --> 00:07:51,220 in this fictional game. 178 00:07:51,220 --> 00:07:52,840 So I'm gonna right-click on the project here, 179 00:07:52,840 --> 00:07:55,220 and we're gonna create a new Python file. 180 00:07:55,220 --> 00:07:57,200 Select Python file, we're gonna call this enemy, 181 00:07:57,200 --> 00:08:00,320 making sure it's a lowercase E at the start there. 182 00:08:00,320 --> 00:08:03,010 And click on okay, or press enter. 183 00:08:03,010 --> 00:08:05,130 And we're gonna work on this class now. 184 00:08:05,130 --> 00:08:06,530 Now we're gonna store hit points 185 00:08:06,530 --> 00:08:08,450 and also the number of lives, 186 00:08:08,450 --> 00:08:10,950 and we're gonna need to initialise the attributes for those. 187 00:08:10,950 --> 00:08:12,560 And we should also give the enemy a name. 188 00:08:12,560 --> 00:08:16,720 So let's start with a class definition, class enemy. 189 00:08:18,510 --> 00:08:22,510 And we'll do a def, parameter constructor, init. 190 00:08:23,980 --> 00:08:25,860 And we're going to include some extra parameters, 191 00:08:25,860 --> 00:08:27,610 so name equals enemy, 192 00:08:29,250 --> 00:08:32,830 and hit underscore points is equal to zero, 193 00:08:34,850 --> 00:08:37,020 and lives is equal to one. 194 00:08:40,270 --> 00:08:43,770 Then we're gonna do self.name equals name, 195 00:08:46,570 --> 00:08:50,770 self.hit underscore points equals hit points. 196 00:08:50,770 --> 00:08:53,520 And then self.lives equals lives. 197 00:08:56,340 --> 00:08:58,100 So this is a superclass, 198 00:08:58,100 --> 00:09:01,040 and any class that extends this class or inherits, 199 00:09:01,040 --> 00:09:03,780 or inherits from this class, enemy, 200 00:09:03,780 --> 00:09:07,380 should always have name, hit points, and lives attributes, 201 00:09:07,380 --> 00:09:10,020 and in the game scenario, it's probably quite reasonable 202 00:09:10,020 --> 00:09:14,240 to assume that any enemy would have those attributes. 203 00:09:14,240 --> 00:09:16,560 But let's also add a method, 204 00:09:16,560 --> 00:09:18,970 which we'll call take damage. 205 00:09:20,420 --> 00:09:23,020 So we're gonna do a def, take underscore damage, 206 00:09:23,020 --> 00:09:24,930 to create a new method. 207 00:09:25,780 --> 00:09:29,370 And it's going to have one parameter, damage. 208 00:09:29,370 --> 00:09:32,290 And we're gonna do remaining points 209 00:09:34,790 --> 00:09:38,960 is equal to self.hit underscore points, take damage. 210 00:09:41,110 --> 00:09:44,550 Then we're gonna put if, remaining points, 211 00:09:44,550 --> 00:09:47,860 is greater than or equal to zero, 212 00:09:47,860 --> 00:09:51,610 then we're gonna do self.hit underscore points 213 00:09:51,610 --> 00:09:54,130 equals remaining points, 214 00:09:54,130 --> 00:09:55,550 then we're gonna print a message. 215 00:09:55,550 --> 00:09:59,300 Print, I took, placement field points damage, 216 00:10:03,120 --> 00:10:07,290 and have, in another replacement field, left.format. 217 00:10:08,890 --> 00:10:13,050 We're going to do damage comma self.hit underscore points. 218 00:10:15,420 --> 00:10:19,350 And we're gonna have an else there, else, 219 00:10:19,350 --> 00:10:21,680 self.lives minus equals one. 220 00:10:24,220 --> 00:10:27,140 So what we're doing here is we're subtracting the damage 221 00:10:27,140 --> 00:10:29,470 from the number of hit points that the enemy has, 222 00:10:29,470 --> 00:10:32,260 and then checking to see if they've still got any left 223 00:10:32,260 --> 00:10:34,590 after that damage is inflicted. 224 00:10:34,590 --> 00:10:37,200 Now if the number remaining is zero or more, 225 00:10:37,200 --> 00:10:39,310 we update the hit points and print a message 226 00:10:39,310 --> 00:10:41,000 showing how much damage was taken, 227 00:10:41,000 --> 00:10:43,700 and also how many hit points are still left. 228 00:10:43,700 --> 00:10:46,170 But if, however, their hit points drop below zero, 229 00:10:46,170 --> 00:10:48,490 then we take a life off instead. 230 00:10:48,490 --> 00:10:49,750 Now we should probably check to see 231 00:10:49,750 --> 00:10:51,320 if we've got any lives left, 232 00:10:51,320 --> 00:10:53,280 but we're demonstrating concepts here, 233 00:10:53,280 --> 00:10:55,210 we're not creating a full game. 234 00:10:55,210 --> 00:10:56,650 This could be a useful exercise 235 00:10:56,650 --> 00:10:58,560 for you to try it yourself, though, 236 00:10:58,560 --> 00:10:59,780 to make sure you've understood 237 00:10:59,780 --> 00:11:02,220 what we've covered in this tutorial. 238 00:11:02,220 --> 00:11:04,470 All right, so we've got a basic class here. 239 00:11:04,470 --> 00:11:07,360 We're storing the name, hit points, and lives, 240 00:11:07,360 --> 00:11:09,780 and we've got a constructor where we can set, 241 00:11:09,780 --> 00:11:13,670 where we do set the initial value of those attributes. 242 00:11:13,670 --> 00:11:15,220 So I'm gonna add another method, 243 00:11:15,220 --> 00:11:16,770 which is basically a copy of this 244 00:11:16,770 --> 00:11:19,960 string method from the player class. 245 00:11:19,960 --> 00:11:21,670 Even though I could probably just copy it and change it, 246 00:11:21,670 --> 00:11:24,170 I'll just type it in, 'cause it's fairly short. 247 00:11:24,170 --> 00:11:25,630 So underscore underscore string, 248 00:11:25,630 --> 00:11:28,630 underscore underscore, self, 249 00:11:28,630 --> 00:11:30,730 and then we're gonna return, 250 00:11:30,730 --> 00:11:33,660 and it's going to be name, colon, 251 00:11:33,660 --> 00:11:35,940 starting your left replacement field, 252 00:11:35,940 --> 00:11:39,020 which is left curly brace, zero.name, 253 00:11:40,270 --> 00:11:44,640 right curly brace, comma, lives, colon, space, 254 00:11:44,640 --> 00:11:47,060 left curly brace, zero.lives, 255 00:11:47,980 --> 00:11:52,360 right curly brace, comma, space, hit points, 256 00:11:52,360 --> 00:11:56,530 colon, space, left curly brace, zero.hit underscore points, 257 00:11:57,630 --> 00:12:00,130 right curly brace.format self. 258 00:12:03,640 --> 00:12:06,140 Okay, so that's actually it. 259 00:12:06,140 --> 00:12:08,410 So okay, and we're using this to print out the attributes, 260 00:12:08,410 --> 00:12:10,200 so we don't have to keep writing long print statements 261 00:12:10,200 --> 00:12:12,370 to check that everything's working. 262 00:12:12,370 --> 00:12:14,400 Okay, so that stuff, that's similar to stuff 263 00:12:14,400 --> 00:12:17,440 I've already covered in earlier videos in this section. 264 00:12:17,440 --> 00:12:18,910 Now, we're not going to actually 265 00:12:18,910 --> 00:12:21,520 create enemy objects directly, 266 00:12:21,520 --> 00:12:23,760 although we could do that if we wanted to. 267 00:12:23,760 --> 00:12:27,570 But this is really just for use as a base class, 268 00:12:27,570 --> 00:12:29,680 so that all the specific enemies 269 00:12:29,680 --> 00:12:31,560 have these basic properties. 270 00:12:31,560 --> 00:12:33,340 So think about like a bird class. 271 00:12:33,340 --> 00:12:35,170 You don't get animals that are just birds. 272 00:12:35,170 --> 00:12:37,520 They're a particular type of bird. 273 00:12:37,520 --> 00:12:39,850 So I'm gonna create one enemy, enemy object, 274 00:12:39,850 --> 00:12:41,780 just to test the class, though, 275 00:12:41,780 --> 00:12:44,260 to make sure that everything's working 276 00:12:44,260 --> 00:12:46,330 before we go extending the class. 277 00:12:46,330 --> 00:12:49,080 So I'll go back to the main file. 278 00:12:50,380 --> 00:12:51,780 We're gonna delete all the code, now, 279 00:12:51,780 --> 00:12:53,750 that we've used to test the player class. 280 00:12:53,750 --> 00:12:56,430 So let's just delete all of that. 281 00:12:56,430 --> 00:12:58,700 Then we'll start on line five. 282 00:12:58,700 --> 00:13:02,870 And line five we're gonna type from enemy, import enemy. 283 00:13:07,220 --> 00:13:09,820 Then we're gonna do random underscore monster 284 00:13:09,820 --> 00:13:12,570 is equal to Enemy, capital E. 285 00:13:12,570 --> 00:13:16,230 And we'll just say, we'll call it basic enemy, 286 00:13:16,230 --> 00:13:17,900 then pass 12 for the number of hit points, 287 00:13:17,900 --> 00:13:20,130 and one for the number of lives. 288 00:13:20,130 --> 00:13:23,580 Then we're gonna print the random monster, 289 00:13:23,580 --> 00:13:24,420 then we're gonna do 290 00:13:24,420 --> 00:13:28,000 random monster.take underscore damage four, 291 00:13:29,170 --> 00:13:31,940 then we're gonna print random monster. 292 00:13:31,940 --> 00:13:33,200 Okay. 293 00:13:33,200 --> 00:13:37,190 Let's just run that and see if it's gonna work for us. 294 00:13:37,190 --> 00:13:39,510 And see, we've created the basic enemy, 295 00:13:39,510 --> 00:13:42,310 lives one, hit points 12, took four points of damage 296 00:13:42,310 --> 00:13:44,120 and they've got eight points left, 297 00:13:44,120 --> 00:13:45,280 eight hit points left, 298 00:13:45,280 --> 00:13:48,790 and we got confirmation at the second printout. 299 00:13:48,790 --> 00:13:50,010 All right, so let's take the, 300 00:13:50,010 --> 00:13:52,750 or let's test the take damage method a bit more. 301 00:13:52,750 --> 00:13:56,220 Let's see what happens when the hit points drop below zero. 302 00:13:56,220 --> 00:13:57,360 And actually, I'll clean this up completely 303 00:13:57,360 --> 00:13:59,520 and put this back onto line one. 304 00:13:59,520 --> 00:14:03,390 We don't need a player at all for now. 305 00:14:03,390 --> 00:14:06,030 So let's add a couple of extra lines here. 306 00:14:06,030 --> 00:14:08,690 So we'll do another eight there. 307 00:14:09,550 --> 00:14:11,250 It should take it to zero hit points, 308 00:14:11,250 --> 00:14:12,750 and then we'll do another one that takes another nine, 309 00:14:12,750 --> 00:14:14,250 just to see what happens. 310 00:14:14,250 --> 00:14:16,500 So let's actually run this. 311 00:14:17,670 --> 00:14:20,220 And you can see, we've got a basic enemy 12, 312 00:14:20,220 --> 00:14:22,520 lost four points, eight left, 313 00:14:22,520 --> 00:14:25,680 it had eight and then lost eight to have zero left. 314 00:14:25,680 --> 00:14:27,010 And then we've just got the printouts. 315 00:14:27,010 --> 00:14:29,810 The lives, you can see there, has dropped down to zero. 316 00:14:29,810 --> 00:14:31,210 So that's working fine. 317 00:14:31,210 --> 00:14:33,320 I do suggest you always test all the paths 318 00:14:33,320 --> 00:14:34,600 throughout your code. 319 00:14:34,600 --> 00:14:36,650 So if you put in some conditions like we did, 320 00:14:36,650 --> 00:14:39,320 when we check for the hit points dropping to below zero, 321 00:14:39,320 --> 00:14:40,790 they'll make sure you use data 322 00:14:40,790 --> 00:14:43,750 that will test the alternative path 323 00:14:43,750 --> 00:14:44,960 to make sure it works as well as 324 00:14:44,960 --> 00:14:48,330 the path you're assuming will work most of the time. 325 00:14:48,330 --> 00:14:50,290 All right, so I'm gonna finish the video here. 326 00:14:50,290 --> 00:14:51,590 In the next video, we're going to start 327 00:14:51,590 --> 00:14:52,990 getting into the good stuff. 328 00:14:52,990 --> 00:14:55,470 We're going to start inheriting from that class, 329 00:14:55,470 --> 00:14:57,450 and this is where it's going to be getting interesting. 330 00:14:57,450 --> 00:14:59,960 So I will see you in the next video.