1 00:00:05,320 --> 00:00:07,840 Okay, so here's where it gets interesting 2 00:00:07,840 --> 00:00:09,480 when we look at extending this class 3 00:00:09,480 --> 00:00:11,440 that we created in the previous video. 4 00:00:11,440 --> 00:00:15,090 I'm talking about the enemy class. 5 00:00:15,090 --> 00:00:18,020 So let's talk about having specific types of enemies 6 00:00:18,020 --> 00:00:18,960 because the code work 7 00:00:18,960 --> 00:00:20,600 that we've currently got in that enemy class 8 00:00:20,600 --> 00:00:23,350 is of a very generic nature as you can see here. 9 00:00:23,350 --> 00:00:24,890 So let's assume that we've got several 10 00:00:24,890 --> 00:00:26,540 different types of enemies. 11 00:00:26,540 --> 00:00:29,480 For example, let's start off and create a new class 12 00:00:29,480 --> 00:00:31,450 and we're gonna call that one troll. 13 00:00:31,450 --> 00:00:34,500 Now one of the enemies our player will have to face 14 00:00:34,500 --> 00:00:35,980 will be a troll. 15 00:00:35,980 --> 00:00:38,180 Now the reason we've been using a separate file 16 00:00:38,180 --> 00:00:40,270 for our player and enemy classes 17 00:00:40,270 --> 00:00:44,120 is to make it easier to switch between them in IntelliJ 18 00:00:44,120 --> 00:00:45,950 so that we can examine the code 19 00:00:45,950 --> 00:00:48,650 without having to scroll around too much. 20 00:00:48,650 --> 00:00:49,940 Now there's not actually much code 21 00:00:49,940 --> 00:00:52,000 in this enemy class at the moment 22 00:00:52,000 --> 00:00:54,400 and troll is gonna be a subclass of enemy 23 00:00:54,400 --> 00:00:56,780 so what I'm going to do is put our new troll class 24 00:00:56,780 --> 00:01:00,190 in the enemy.py file which I've got activated now 25 00:01:00,190 --> 00:01:02,490 along with the enemy class. 26 00:01:02,490 --> 00:01:04,580 Now the Python style guide recommends 27 00:01:04,580 --> 00:01:07,500 leaving two blank lines between classes. 28 00:01:07,500 --> 00:01:11,870 So therefore, I'm going to actually start on line 20. 29 00:01:11,870 --> 00:01:14,540 All right, so class Troll Enemy. 30 00:01:20,060 --> 00:01:21,600 So that looks a bit different. 31 00:01:21,600 --> 00:01:23,670 What have I actually done here? 32 00:01:23,670 --> 00:01:26,390 Well, as I've said that troll would inherit from enemy, 33 00:01:26,390 --> 00:01:27,350 you've probably guessed 34 00:01:27,350 --> 00:01:30,120 that this is how you create a subclass. 35 00:01:30,120 --> 00:01:32,350 Now a subclass remember is a class 36 00:01:32,350 --> 00:01:35,330 that inherits from another class. 37 00:01:35,330 --> 00:01:36,790 Now you may also hear it described 38 00:01:36,790 --> 00:01:39,510 that troll extends the enemy class, 39 00:01:39,510 --> 00:01:41,640 they both mean the same thing. 40 00:01:41,640 --> 00:01:45,550 Now in fact, our enemy class is itself a subclass 41 00:01:45,550 --> 00:01:48,090 and that's because each class in Python 3 42 00:01:48,090 --> 00:01:52,320 ultimately inherits from a built-in class called object. 43 00:01:52,320 --> 00:01:55,650 Now we haven't specified that on line one, 44 00:01:55,650 --> 00:01:57,760 but we declared the enemy class 45 00:01:57,760 --> 00:02:00,570 and that's because Python 3 allows a shortcut 46 00:02:00,570 --> 00:02:03,510 for a class that has no super class other than object 47 00:02:03,510 --> 00:02:06,780 so a class, in other words, inherits directly from object. 48 00:02:06,780 --> 00:02:10,410 So in Python 3, we've got on line one this class enemy. 49 00:02:10,410 --> 00:02:13,550 I'm just gonna comment that out. 50 00:02:13,550 --> 00:02:15,750 That's exactly the same as typing it this way, 51 00:02:15,750 --> 00:02:17,330 class Enemy object. 52 00:02:20,980 --> 00:02:23,750 So both declarations do exactly the same thing. 53 00:02:23,750 --> 00:02:28,040 They define a class called enemy that inherits from object. 54 00:02:28,040 --> 00:02:30,990 Now the reason I've been saying in Python 3 55 00:02:30,990 --> 00:02:33,830 is because this wasn't the case in Python 2. 56 00:02:33,830 --> 00:02:37,230 Now in Python 2, that commented out declaration 57 00:02:37,230 --> 00:02:41,020 would produce an old style class that behaves differently 58 00:02:41,020 --> 00:02:45,140 to the new style classes you get by subclassing object. 59 00:02:45,140 --> 00:02:49,630 However, in Python 3, there are only the new style classes 60 00:02:49,630 --> 00:02:51,930 and they automatically inherit from object 61 00:02:51,930 --> 00:02:53,930 even if you don't specify it 62 00:02:53,930 --> 00:02:56,010 so even if you use a commented out form 63 00:02:56,010 --> 00:02:57,990 in other words on line one. 64 00:02:57,990 --> 00:03:00,180 Now this is a Python 3 course 65 00:03:00,180 --> 00:03:02,490 so we're not really interested in the difference, 66 00:03:02,490 --> 00:03:04,370 but I wanted to make you aware of it 67 00:03:04,370 --> 00:03:06,830 so that you always use the second form 68 00:03:06,830 --> 00:03:10,900 with object in parenthesis if you have to use Python 2 69 00:03:10,900 --> 00:03:13,140 and wanna use the new style classes. 70 00:03:13,140 --> 00:03:14,500 For that reason, it might be worthwhile 71 00:03:14,500 --> 00:03:17,500 developing the habit of always using the second form. 72 00:03:17,500 --> 00:03:20,260 Of course, if you find yourself working on Python 2 code 73 00:03:20,260 --> 00:03:23,420 that uses the first form of the class without object, 74 00:03:23,420 --> 00:03:25,070 then don't go refactoring it 75 00:03:25,070 --> 00:03:27,310 without a great deal of thought. 76 00:03:27,310 --> 00:03:28,650 In Python 2, you could change 77 00:03:28,650 --> 00:03:30,850 the entire behaviour of the programme 78 00:03:30,850 --> 00:03:34,770 just by changing class enemy as I've got on line one here, 79 00:03:34,770 --> 00:03:35,600 up here at the top here, 80 00:03:35,600 --> 00:03:37,980 to line two class Enemy object, 81 00:03:37,980 --> 00:03:39,540 but again that's Python 2. 82 00:03:39,540 --> 00:03:41,890 Not a problem with Python 3 83 00:03:41,890 --> 00:03:43,900 which we're using in this course. 84 00:03:43,900 --> 00:03:46,090 Okay, so back to troll, 85 00:03:46,090 --> 00:03:49,100 so our troll class will inherit from enemy 86 00:03:49,100 --> 00:03:52,930 and it'll have to access or have access to the attributes 87 00:03:52,930 --> 00:03:54,770 that we defined in enemy. 88 00:03:54,770 --> 00:03:57,990 The takeout is called damage method for example. 89 00:03:57,990 --> 00:04:00,400 Now we really should write a constructor, 90 00:04:00,400 --> 00:04:02,630 the init method for this troll class, 91 00:04:02,630 --> 00:04:05,640 but let's start by saying what happens if we don't. 92 00:04:05,640 --> 00:04:08,670 Now the first thing that's happening is we've got an error, 93 00:04:08,670 --> 00:04:10,340 indent expected, 94 00:04:10,340 --> 00:04:12,750 and that's because Python expects there to be some code 95 00:04:12,750 --> 00:04:14,720 after the class declaration, 96 00:04:14,720 --> 00:04:17,620 but we don't wanna provide any just yet. 97 00:04:17,620 --> 00:04:19,940 Now fortunately, there's a very useful command 98 00:04:19,940 --> 00:04:22,680 called pass that doesn't do anything 99 00:04:22,680 --> 00:04:25,430 so I can just type that in there. 100 00:04:27,240 --> 00:04:29,180 So pass doesn't do anything at all, 101 00:04:29,180 --> 00:04:30,560 but unlike a comment, 102 00:04:30,560 --> 00:04:32,950 it doesn't get ignored by the compiler. 103 00:04:32,950 --> 00:04:35,780 So by including it in instruction that does nothing, 104 00:04:35,780 --> 00:04:37,790 we've removed the syntax error 105 00:04:37,790 --> 00:04:41,410 and our code will ultimately be able to run. 106 00:04:41,410 --> 00:04:44,420 Now it may seem strange that an instruction to do nothing 107 00:04:44,420 --> 00:04:45,820 is very useful, 108 00:04:45,820 --> 00:04:49,560 but you'll come across pass in all sorts of places. 109 00:04:49,560 --> 00:04:52,350 Now you may wanna catch an error, an exception, 110 00:04:52,350 --> 00:04:54,990 that we've covered in section 13 111 00:04:54,990 --> 00:04:56,840 to prevent the programme crashing, 112 00:04:56,840 --> 00:04:59,700 but don't wanna do anything if the error happens. 113 00:04:59,700 --> 00:05:03,220 For example, if your programme is reading a load of data 114 00:05:03,220 --> 00:05:05,840 that was provided by people completing the survey, 115 00:05:05,840 --> 00:05:07,830 you may have to convert their date of birth 116 00:05:07,830 --> 00:05:09,740 into a valid Python date. 117 00:05:09,740 --> 00:05:12,280 Now some people would rather not give their date of birth, 118 00:05:12,280 --> 00:05:14,460 so that particular field could be blank. 119 00:05:14,460 --> 00:05:15,650 So you could trap the error 120 00:05:15,650 --> 00:05:19,190 when the code tries to convert no input into a date, 121 00:05:19,190 --> 00:05:21,270 but there's no action that needs to be taken, 122 00:05:21,270 --> 00:05:23,030 you just wanna skip that field 123 00:05:23,030 --> 00:05:27,140 and continue passing or continue processing the data. 124 00:05:27,140 --> 00:05:29,180 So that's a good time to use pass 125 00:05:29,180 --> 00:05:30,510 so that you can catch the error 126 00:05:30,510 --> 00:05:32,950 but continue without doing anything. 127 00:05:32,950 --> 00:05:35,040 So you can find more information on pass 128 00:05:35,040 --> 00:05:36,510 in the documentation. 129 00:05:36,510 --> 00:05:38,090 But rather than give you a link this time, 130 00:05:38,090 --> 00:05:40,620 I'm gonna show you one thing that may be confusing 131 00:05:40,620 --> 00:05:43,090 when you search for Python documentation 132 00:05:43,090 --> 00:05:45,190 using a search engine. 133 00:05:45,190 --> 00:05:47,020 So if I open a browser 134 00:05:48,500 --> 00:05:51,410 and do a search for pass in Python, 135 00:05:54,880 --> 00:05:56,660 we've got stack overflow tutorials, 136 00:05:56,660 --> 00:05:58,700 important stack flow, et cetera, 137 00:05:58,700 --> 00:06:00,480 but I suggest always starting with links 138 00:06:00,480 --> 00:06:02,800 to the Python documentation. 139 00:06:02,800 --> 00:06:04,870 But with that said, you'll often find references 140 00:06:04,870 --> 00:06:08,100 when you're searching for general Python information 141 00:06:08,100 --> 00:06:10,200 to links that are Python 2.7, 142 00:06:10,200 --> 00:06:13,000 as is the case in this fourth link here, 143 00:06:13,000 --> 00:06:16,020 and obviously we want the Python 3 documentation. 144 00:06:16,020 --> 00:06:19,190 Now the Python 2 documentation tends to be returned 145 00:06:19,190 --> 00:06:21,550 because of the way the document is organised 146 00:06:21,550 --> 00:06:24,170 so click the link anyway 147 00:06:24,170 --> 00:06:27,230 and ignore the fact that it's for Python 2. 148 00:06:27,230 --> 00:06:28,380 Then not surprisingly, 149 00:06:28,380 --> 00:06:31,150 we get the documentation coming up for Python 2, 150 00:06:31,150 --> 00:06:32,730 2.7 in this case, 151 00:06:32,730 --> 00:06:35,720 but as you can see up in the top left is a dropdown 152 00:06:35,720 --> 00:06:37,860 that lets you choose which version of Python 153 00:06:37,860 --> 00:06:39,180 you're interested in. 154 00:06:39,180 --> 00:06:41,950 So you can choose 3.5 from there 155 00:06:41,950 --> 00:06:44,200 and I recommend you do that 156 00:06:45,230 --> 00:06:46,860 to make sure the information you're getting 157 00:06:46,860 --> 00:06:48,560 is for the right version. 158 00:06:48,560 --> 00:06:49,810 So don't rule out those links 159 00:06:49,810 --> 00:06:52,230 because they mention the earlier version of Python. 160 00:06:52,230 --> 00:06:54,750 Once you get to the docs.python.org site 161 00:06:54,750 --> 00:06:56,610 like where we are now, 162 00:06:56,610 --> 00:06:58,710 you can still choose the version of Python 163 00:06:58,710 --> 00:07:00,440 that you're interested in. 164 00:07:00,440 --> 00:07:02,660 Now Python 3.6 haven't been released 165 00:07:02,660 --> 00:07:04,560 at the time of recording this video, 166 00:07:04,560 --> 00:07:07,160 but what it is you'll be able to get the documentation 167 00:07:07,160 --> 00:07:09,540 for that version from here as well. 168 00:07:09,540 --> 00:07:12,830 The same for Python 3.7 which is still in development. 169 00:07:12,830 --> 00:07:15,640 Okay, back to our main programme, 170 00:07:15,640 --> 00:07:17,360 so I'm gonna go back to main 171 00:07:17,360 --> 00:07:21,980 and what we need to do now is import enemy and troll 172 00:07:21,980 --> 00:07:24,940 without having to qualify them with a module name 173 00:07:24,940 --> 00:07:27,190 so that we don't have to write enemy.troll 174 00:07:27,190 --> 00:07:29,440 whenever we wanna create a new troll instance. 175 00:07:29,440 --> 00:07:31,870 So I can put from enemy import Enemy 176 00:07:31,870 --> 00:07:34,330 and we can just put a comma 177 00:07:34,330 --> 00:07:35,160 Troll 178 00:07:36,160 --> 00:07:38,150 and we're getting that warning because it's unused 179 00:07:38,150 --> 00:07:41,020 but that we're going to change shortly. 180 00:07:41,020 --> 00:07:43,070 Now we don't really wanna use the enemy class anymore, 181 00:07:43,070 --> 00:07:44,350 but before I delete it, 182 00:07:44,350 --> 00:07:47,130 I just wanted to show you how to import several classes 183 00:07:47,130 --> 00:07:48,850 from the same module. 184 00:07:48,850 --> 00:07:52,370 All right, so let's go down here on line 15 185 00:07:52,370 --> 00:07:55,870 and we'll put ugly_troll is equal to Troll 186 00:07:59,090 --> 00:08:03,260 then we gotta do print Ugly troll replacement field 187 00:08:06,600 --> 00:08:08,190 .format ugly_troll. 188 00:08:11,370 --> 00:08:12,790 Okay, we run that 189 00:08:14,880 --> 00:08:15,760 and we can see down at the bottom, 190 00:08:15,760 --> 00:08:17,440 the ugly troll printout 191 00:08:17,440 --> 00:08:20,040 or the ugly troll information is being displayed, 192 00:08:20,040 --> 00:08:21,680 but it's not too good at the moment though. 193 00:08:21,680 --> 00:08:24,090 The name is still enemy as you can see 194 00:08:24,090 --> 00:08:25,910 in the output down at the bottom 195 00:08:25,910 --> 00:08:27,760 and the troll has got no hit points 196 00:08:27,760 --> 00:08:29,040 so it's probably not gonna be 197 00:08:29,040 --> 00:08:31,340 a very challenging enemy to fight. 198 00:08:31,340 --> 00:08:33,169 Now we didn't add an init method 199 00:08:33,169 --> 00:08:34,919 so creating a troll like this 200 00:08:34,919 --> 00:08:38,320 uses the default values for the enemy class. 201 00:08:38,320 --> 00:08:41,510 Now the enemy class init method takes three arguments 202 00:08:41,510 --> 00:08:43,320 so we can create another troll 203 00:08:43,320 --> 00:08:46,710 and pass some values to the constructor. 204 00:08:46,710 --> 00:08:49,490 All right, so let's remove the code that created our enemy 205 00:08:49,490 --> 00:08:51,430 so we're just working with trolls now. 206 00:08:51,430 --> 00:08:54,860 So I'm gonna delete all this right up to there 207 00:08:54,860 --> 00:08:57,620 because we don't need the enemy anymore 208 00:08:57,620 --> 00:09:01,360 and then we'll add another troll as well 209 00:09:01,360 --> 00:09:05,530 so we'll put another_troll is equal to Troll Ug, 18, 1 210 00:09:11,720 --> 00:09:15,310 and we'll do a printout print another_troll 211 00:09:17,020 --> 00:09:21,190 replacement field so no output .format and another_troll. 212 00:09:25,630 --> 00:09:29,320 So this time I've created another troll with the name Ug 213 00:09:29,320 --> 00:09:32,750 that takes or has 18 hit points. 214 00:09:32,750 --> 00:09:36,280 All right, so let's create another troll, Ug's brother, 215 00:09:36,280 --> 00:09:40,450 he's called Urg so we'll call it brother equals Troll, 216 00:09:45,190 --> 00:09:48,040 we'll call him Urg and this guy's a bit of a brute 217 00:09:48,040 --> 00:09:49,750 even by troll standards 218 00:09:49,750 --> 00:09:51,980 and he can take 23 hit points and damage 219 00:09:51,980 --> 00:09:55,480 so let's set that to 23 and print brother. 220 00:09:58,420 --> 00:10:00,590 Now if you're used to overloaded constructors 221 00:10:00,590 --> 00:10:02,500 in languages such as Java, 222 00:10:02,500 --> 00:10:04,260 then you'd probably be quite happy 223 00:10:04,260 --> 00:10:05,630 with what's going on here, 224 00:10:05,630 --> 00:10:08,880 even if you can't quite work out how Python is doing it. 225 00:10:08,880 --> 00:10:10,300 But if you've never used another language, 226 00:10:10,300 --> 00:10:12,970 then this might be a bit confusing what I've just done. 227 00:10:12,970 --> 00:10:15,380 So when you overload a method 228 00:10:15,380 --> 00:10:17,040 in other programming languages, 229 00:10:17,040 --> 00:10:19,840 you provide a method with exactly the same name 230 00:10:19,840 --> 00:10:22,300 but taking different arguments. 231 00:10:22,300 --> 00:10:26,280 So the ugly troll constructor on line three 232 00:10:26,280 --> 00:10:28,100 doesn't take any arguments 233 00:10:28,100 --> 00:10:31,670 and another_troll constructor on line six 234 00:10:31,670 --> 00:10:33,800 takes or gets three arguments 235 00:10:33,800 --> 00:10:36,810 and his brother Urg on line nine 236 00:10:36,810 --> 00:10:38,700 and he has two arguments. 237 00:10:38,700 --> 00:10:41,420 Now in Java, you'd need to write three constructors, 238 00:10:41,420 --> 00:10:43,350 one for each case. 239 00:10:43,350 --> 00:10:45,350 However, Python doesn't have the concept 240 00:10:45,350 --> 00:10:47,320 of overloaded methods. 241 00:10:47,320 --> 00:10:48,630 Now if you try, 242 00:10:48,630 --> 00:10:50,890 the last method that you defined in the code 243 00:10:50,890 --> 00:10:53,430 will be the only one that exists. 244 00:10:53,430 --> 00:10:56,520 Now if you haven't used another object oriented language, 245 00:10:56,520 --> 00:10:58,270 then don't worry about that last bit, 246 00:10:58,270 --> 00:11:00,090 overloaded methods and so forth, 247 00:11:00,090 --> 00:11:01,930 because Python doesn't have them 248 00:11:01,930 --> 00:11:04,380 and I'm gonna be explaining how all this is working 249 00:11:04,380 --> 00:11:05,290 in a minute. 250 00:11:05,290 --> 00:11:08,280 But for those who have come from other languages 251 00:11:08,280 --> 00:11:11,340 and thinking this looks like method overloading, 252 00:11:11,340 --> 00:11:12,680 it actually isn't, 253 00:11:12,680 --> 00:11:15,900 but it is how you achieve the same thing in Python. 254 00:11:15,900 --> 00:11:18,820 All we've done here is use optional name to parameters 255 00:11:18,820 --> 00:11:21,480 in the enemy class init method. 256 00:11:21,480 --> 00:11:23,830 And it's really now different from using the print method 257 00:11:23,830 --> 00:11:27,080 to print things out because on line 10, 258 00:11:27,080 --> 00:11:28,680 we print brother 259 00:11:28,680 --> 00:11:31,480 and that's the only argument we provided to the function. 260 00:11:31,480 --> 00:11:33,500 Printout does take other arguments 261 00:11:33,500 --> 00:11:36,780 so you could specify that there's no end of line character 262 00:11:36,780 --> 00:11:38,000 for example. 263 00:11:38,000 --> 00:11:40,010 So I'm gonna come along here. 264 00:11:40,010 --> 00:11:43,980 Actually, let's do it on line seven, so another_troll, 265 00:11:43,980 --> 00:11:45,070 and you save this before encoding 266 00:11:45,070 --> 00:11:48,580 and equals and two double quotes, 267 00:11:48,580 --> 00:11:50,350 an empty string in other words, 268 00:11:50,350 --> 00:11:51,940 so when we do that, 269 00:11:53,570 --> 00:11:57,100 we find the another_troll Urg and his brother argument 270 00:11:57,100 --> 00:11:59,940 and his brother Urg are now printed on the same line 271 00:11:59,940 --> 00:12:01,900 because we've removed the end of line 272 00:12:01,900 --> 00:12:04,440 or replaced that with an empty string. 273 00:12:04,440 --> 00:12:06,300 So this is not the best example 274 00:12:06,300 --> 00:12:08,710 because we have to specify the name end. 275 00:12:08,710 --> 00:12:10,550 That's because the print function 276 00:12:10,550 --> 00:12:12,900 can take any number of strings to print 277 00:12:12,900 --> 00:12:14,080 so just adding another one 278 00:12:14,080 --> 00:12:16,340 to the list of arguments wouldn't work. 279 00:12:16,340 --> 00:12:18,820 But for methods that have a fixed number of arguments, 280 00:12:18,820 --> 00:12:21,750 you can provide them without using their names 281 00:12:21,750 --> 00:12:24,420 as long as you keep them in the same position 282 00:12:24,420 --> 00:12:27,010 that they were specified originally. 283 00:12:27,010 --> 00:12:30,510 So when we don't specify any arguments on line three, 284 00:12:30,510 --> 00:12:32,190 the default values that we specified 285 00:12:32,190 --> 00:12:34,860 in enemy's init method are used. 286 00:12:36,330 --> 00:12:39,730 And you can see we've got name equals enemy, 287 00:12:39,730 --> 00:12:42,460 hit points equal zero, lives equals one. 288 00:12:42,460 --> 00:12:45,200 So obviously the default values 289 00:12:45,200 --> 00:12:49,680 are the ones that are after the equal sign on each. 290 00:12:49,680 --> 00:12:51,060 We're going back here now to main. 291 00:12:51,060 --> 00:12:54,280 On line six, all the values were specified. 292 00:12:54,280 --> 00:12:55,730 And then on line nine, 293 00:12:55,730 --> 00:12:58,830 only the two arguments were specified. 294 00:12:58,830 --> 00:13:03,210 So name in this case on line nine gets the value of Urg 295 00:13:03,210 --> 00:13:05,530 and hit points gets the value of 23 296 00:13:05,530 --> 00:13:07,610 then the lives were defaulted to one 297 00:13:07,610 --> 00:13:08,900 because of the way we have defined this 298 00:13:08,900 --> 00:13:12,720 as the default value for the lives attribute. 299 00:13:12,720 --> 00:13:14,140 So once again, 300 00:13:14,140 --> 00:13:17,520 if you are used to languages such as Java or C++, 301 00:13:17,520 --> 00:13:21,690 you can't actually overload functions and methods in Python, 302 00:13:21,690 --> 00:13:23,900 but you can generally get the same effect 303 00:13:23,900 --> 00:13:27,120 by using named parameters with default values. 304 00:13:27,120 --> 00:13:29,270 All right, so I'm gonna stop the video here. 305 00:13:29,270 --> 00:13:30,100 In the next video, 306 00:13:30,100 --> 00:13:32,000 we're going to look at making our troll class 307 00:13:32,000 --> 00:13:34,440 a little bit more useful but at the moment, 308 00:13:34,440 --> 00:13:36,550 we could do exactly the same thing 309 00:13:36,550 --> 00:13:38,850 by using the enemy class rather than a troll. 310 00:13:38,850 --> 00:13:39,680 So in other words, 311 00:13:39,680 --> 00:13:43,650 we could come back here and change that to enemy. 312 00:13:43,650 --> 00:13:45,320 And if you run that, 313 00:13:46,740 --> 00:13:48,740 we get exactly the same result. 314 00:13:48,740 --> 00:13:50,810 So although troll is a subclass of enemy, 315 00:13:50,810 --> 00:13:53,140 at the moment it's not a very useful one. 316 00:13:53,140 --> 00:13:55,230 Now in the next video, we'll make some changes 317 00:13:55,230 --> 00:13:57,710 and see the advantages of creating classes 318 00:13:57,710 --> 00:13:59,990 that inherit from another class. 319 00:13:59,990 --> 00:14:00,930 But just before I do that, 320 00:14:00,930 --> 00:14:05,430 I'm gonna remove this and equals part on line seven. 321 00:14:05,430 --> 00:14:08,200 Okay, so I'll see you in the next video.