WEBVTT 1 00:00:00.130 --> 00:00:01.970 Hi guys and welcome back. 2 00:00:01.970 --> 00:00:03.890 In this video we're gonna talk about 3 00:00:03.890 --> 00:00:06.140 object oriented programming. 4 00:00:06.140 --> 00:00:08.790 Object oriented programming is a bit confusing 5 00:00:08.790 --> 00:00:11.070 when you get started, so if you've never seen 6 00:00:11.070 --> 00:00:13.950 object oriented programming before, just take it easy 7 00:00:13.950 --> 00:00:16.410 with the next few videos, watch them a couple of times 8 00:00:16.410 --> 00:00:18.330 if you need to, ask any questions in the course 9 00:00:18.330 --> 00:00:22.000 of the Q and A, if necessary we'll be there to help you out. 10 00:00:22.000 --> 00:00:24.780 Object oriented programming allows us as developers 11 00:00:24.780 --> 00:00:28.260 to write code in a slightly different way 12 00:00:28.260 --> 00:00:30.250 than we would write if we didn't have 13 00:00:30.250 --> 00:00:32.140 object oriented programming. 14 00:00:32.140 --> 00:00:34.900 The purpose of object oriented programming 15 00:00:34.900 --> 00:00:37.274 is to make our life as developers simpler 16 00:00:37.274 --> 00:00:41.641 by allowing us to write code that looks like 17 00:00:41.641 --> 00:00:44.480 what we would work with in the real world 18 00:00:44.480 --> 00:00:46.750 if we were talking about, you know, 19 00:00:46.750 --> 00:00:49.110 real world things like chairs and tables 20 00:00:49.110 --> 00:00:50.640 and printers and things like that, 21 00:00:50.640 --> 00:00:53.860 as opposed to code and data passing 22 00:00:53.860 --> 00:00:55.860 from one function to another. 23 00:00:55.860 --> 00:00:58.250 So that is the purpose of object oriented programming. 24 00:00:58.250 --> 00:00:59.990 And in this video we're going to look at how 25 00:00:59.990 --> 00:01:01.163 it works in Python. 26 00:01:02.260 --> 00:01:05.820 Let's say that you've got a dictionary like this one here 27 00:01:05.820 --> 00:01:09.370 which shows some information about a student. 28 00:01:09.370 --> 00:01:12.920 Now clearly this thing here is not a student, 29 00:01:12.920 --> 00:01:15.160 it is a dictionary that has some data. 30 00:01:15.160 --> 00:01:18.160 And as we know, programming is all about data, 31 00:01:18.160 --> 00:01:20.860 passing data from one place to another and so forth. 32 00:01:20.860 --> 00:01:23.500 So what we've got here is some data that is probably 33 00:01:23.500 --> 00:01:25.810 about a student somewhere in our classroom 34 00:01:25.810 --> 00:01:27.113 or something like that. 35 00:01:27.970 --> 00:01:31.012 Then we've got a function that takes in a sequence 36 00:01:31.012 --> 00:01:35.130 and adds the entire sequence together and divides it 37 00:01:35.130 --> 00:01:37.690 by the length of the sequence and then returns that. 38 00:01:37.690 --> 00:01:40.630 So it gives you the average of a sequence. 39 00:01:40.630 --> 00:01:43.120 For example we could use it to calculate the average 40 00:01:43.120 --> 00:01:45.180 grade of Rolf. 41 00:01:45.180 --> 00:01:46.520 How would you do that? 42 00:01:46.520 --> 00:01:48.739 Well you would have to use the function 43 00:01:48.739 --> 00:01:52.160 and give to it Rolf's grades. 44 00:01:52.160 --> 00:01:57.160 So you do average student grades, like that. 45 00:01:58.380 --> 00:02:01.540 So if we run that you'll see that we get out 46 00:02:01.540 --> 00:02:05.760 the value 88.0 which is the average grade. 47 00:02:05.760 --> 00:02:09.230 However, there is something about this function 48 00:02:09.230 --> 00:02:13.190 which is very important when you are thinking 49 00:02:13.190 --> 00:02:14.490 about object oriented programming, 50 00:02:14.490 --> 00:02:17.236 which is that this function doesn't know anything 51 00:02:17.236 --> 00:02:20.761 about the student. 52 00:02:20.761 --> 00:02:25.050 The function only operates on the input that it receives 53 00:02:25.050 --> 00:02:27.510 and that could be a set of student grades 54 00:02:27.510 --> 00:02:29.393 or it could be something else. 55 00:02:30.713 --> 00:02:34.850 So when we as developers are talking specifically 56 00:02:34.850 --> 00:02:37.460 about a student and we want to calculate specifically 57 00:02:37.460 --> 00:02:42.460 the average student grade for Rolf, it is much nicer 58 00:02:42.690 --> 00:02:46.435 if we can say hey student, what's your average 59 00:02:46.435 --> 00:02:51.170 as opposed to get the average of this sequence 60 00:02:51.170 --> 00:02:54.490 that could or could not be related to the student. 61 00:02:54.490 --> 00:02:59.462 So basically what I want to do is student.average. 62 00:02:59.462 --> 00:03:02.240 This is what object oriented programming 63 00:03:02.240 --> 00:03:04.430 will allow us to do. 64 00:03:04.430 --> 00:03:09.130 But in order to do that, student cannot be a dictionary 65 00:03:09.130 --> 00:03:12.180 because dictionaries you can't do that on. 66 00:03:12.180 --> 00:03:16.330 You have to code your own thing in Python that will 67 00:03:16.330 --> 00:03:21.180 allow you to call the average method inside it, 68 00:03:21.180 --> 00:03:24.390 and that will give you the average of the student. 69 00:03:24.390 --> 00:03:26.820 So it is a very different approach, 70 00:03:26.820 --> 00:03:30.760 and it is not necessarily superior, 71 00:03:30.760 --> 00:03:32.280 but it is different and allows 72 00:03:32.280 --> 00:03:35.000 you to think of your programmes in a different way. 73 00:03:35.000 --> 00:03:37.920 So let's rewrite this example here using object 74 00:03:37.920 --> 00:03:41.830 oriented programming so you'll have a look at the syntax. 75 00:03:41.830 --> 00:03:43.470 The syntax for object oriented programming 76 00:03:43.470 --> 00:03:46.900 or to define a class in Python is to type out a keyword 77 00:03:46.900 --> 00:03:50.160 class, and then the name of your class. 78 00:03:50.160 --> 00:03:53.560 So a class is a definition of something, 79 00:03:53.560 --> 00:03:56.680 but it doesn't create a particular student here, 80 00:03:56.680 --> 00:03:58.980 we're only defining how a student will behave. 81 00:04:00.080 --> 00:04:03.870 So you can say inside the function, 82 00:04:03.870 --> 00:04:06.680 notice that there are four spaces of indentation, 83 00:04:06.680 --> 00:04:08.450 you can define functions. 84 00:04:08.450 --> 00:04:10.760 So you can define a special function called 85 00:04:10.760 --> 00:04:15.090 the underscore underscore init underscore underscore. 86 00:04:15.090 --> 00:04:17.500 So this function name is very important, 87 00:04:17.500 --> 00:04:19.010 and it has two underscores at the start 88 00:04:19.010 --> 00:04:20.520 and two at the end. 89 00:04:20.520 --> 00:04:23.880 And then you put your brackets and in here we're going 90 00:04:23.880 --> 00:04:26.040 to type out self. 91 00:04:26.040 --> 00:04:28.610 Although this is again just a variable name 92 00:04:28.610 --> 00:04:30.470 like in every other function and you can call it 93 00:04:30.470 --> 00:04:31.770 whatever you want, it doesn't have to be self 94 00:04:31.770 --> 00:04:35.023 if you don't want, but self is the convention in Python. 95 00:04:36.060 --> 00:04:39.170 Then in the body of the function you can define 96 00:04:39.170 --> 00:04:40.520 anything you want. 97 00:04:40.520 --> 00:04:44.820 For example, self.name is going to be Rolf. 98 00:04:44.820 --> 00:04:48.230 And what this is doing is it is taking whatever self is 99 00:04:50.070 --> 00:04:54.390 and it is accessing the name property inside of self. 100 00:04:54.390 --> 00:04:57.130 So here we're using the dot notation 101 00:04:57.130 --> 00:04:59.420 to access something inside of self, 102 00:04:59.420 --> 00:05:02.060 and what we're accessing is the name property. 103 00:05:02.060 --> 00:05:04.970 And then we're giving it a value of Rolf. 104 00:05:04.970 --> 00:05:09.600 What that means is that when we use this class 105 00:05:09.600 --> 00:05:12.950 to create something, that thing is going 106 00:05:12.950 --> 00:05:14.180 to have a name of Rolf. 107 00:05:14.180 --> 00:05:17.310 So here's how you create a thing from a class. 108 00:05:17.310 --> 00:05:20.297 We can say something like student, notice that now 109 00:05:20.297 --> 00:05:21.580 this is lowercase because this is a new variable 110 00:05:21.580 --> 00:05:23.400 that we're creating right now, 111 00:05:23.400 --> 00:05:28.400 is a student, which is uppercase S because this the class. 112 00:05:28.900 --> 00:05:31.560 And now we're going to tell it to use the class 113 00:05:31.560 --> 00:05:35.160 to create what's called an object in Python 114 00:05:35.160 --> 00:05:38.500 to create a new thing that behaves 115 00:05:38.500 --> 00:05:40.930 like what this class defines. 116 00:05:40.930 --> 00:05:44.380 So when you do this Python creates a new 117 00:05:44.380 --> 00:05:47.460 essentially empty container if you will 118 00:05:47.460 --> 00:05:50.070 and it runs the init method. 119 00:05:50.070 --> 00:05:52.260 By the way it is a method and not a function 120 00:05:52.260 --> 00:05:54.270 because it is inside of a class. 121 00:05:54.270 --> 00:05:55.810 So when a function is inside of a class 122 00:05:55.810 --> 00:05:57.460 it's called a method. 123 00:05:57.460 --> 00:06:00.420 So when you call the student class, 124 00:06:00.420 --> 00:06:02.030 notice that this bracket notation here 125 00:06:02.030 --> 00:06:03.950 is used to call a function normally. 126 00:06:03.950 --> 00:06:05.950 But we can also use it to call a class. 127 00:06:05.950 --> 00:06:08.430 When you call that Python will automatically 128 00:06:08.430 --> 00:06:12.610 call the init method for you and it will create 129 00:06:12.610 --> 00:06:16.720 this empty thing called self, and you will be able 130 00:06:16.720 --> 00:06:20.300 to modify the name property inside self 131 00:06:20.300 --> 00:06:22.080 and give it the value Rolf. 132 00:06:22.080 --> 00:06:24.550 The name property won't exist by default so doing 133 00:06:24.550 --> 00:06:26.990 this also creates it, which is quite nice. 134 00:06:26.990 --> 00:06:31.690 So once that's done and this self object contains 135 00:06:31.690 --> 00:06:36.690 a name property, Python will give you back that self. 136 00:06:37.930 --> 00:06:40.530 And student will become a name 137 00:06:40.530 --> 00:06:43.480 for the self thing we created, 138 00:06:43.480 --> 00:06:46.550 that thing being an object, that's what they're called. 139 00:06:46.550 --> 00:06:49.710 So we're using this class through the init method 140 00:06:49.710 --> 00:06:53.010 to create an object and assign the name property 141 00:06:53.010 --> 00:06:56.170 inside that object to the string Rolf. 142 00:06:56.170 --> 00:06:59.730 Then that object is what becomes the value 143 00:06:59.730 --> 00:07:01.920 for our student variable. 144 00:07:01.920 --> 00:07:05.590 So you can now do print student.name, 145 00:07:05.590 --> 00:07:07.320 and here what we're doing is we're accessing 146 00:07:07.320 --> 00:07:10.340 the name property of our student variable 147 00:07:10.340 --> 00:07:12.760 which as you know is the self 148 00:07:12.760 --> 00:07:17.580 that we created earlier on, so that will give you Rolf. 149 00:07:17.580 --> 00:07:21.940 And if I run that you see that Rolf comes out. 150 00:07:21.940 --> 00:07:25.940 This is how object oriented programming works in Python. 151 00:07:25.940 --> 00:07:29.220 You call a class, the init method runs, 152 00:07:29.220 --> 00:07:31.860 and what you get back is the object you created 153 00:07:31.860 --> 00:07:33.890 and in the init method you have the opportunity 154 00:07:33.890 --> 00:07:36.980 to set and change its properties. 155 00:07:36.980 --> 00:07:38.750 So what we've got here is the name property 156 00:07:38.750 --> 00:07:40.210 that we're changing. 157 00:07:40.210 --> 00:07:43.670 As well as self.name equals Rolf, we can do self.grades 158 00:07:43.670 --> 00:07:45.863 and make it equal to what we had before, 159 00:07:47.290 --> 00:07:48.123 something like that. 160 00:07:48.123 --> 00:07:51.270 So we're making the grades property of self 161 00:07:51.270 --> 00:07:52.670 equal to this tuple. 162 00:07:52.670 --> 00:07:54.720 And then when the function finishes, 163 00:07:54.720 --> 00:07:57.780 the class gives back self to student 164 00:07:57.780 --> 00:08:01.400 and now you can print out student.grades 165 00:08:01.400 --> 00:08:04.550 if you want and that property will exist there as well, 166 00:08:04.550 --> 00:08:05.383 as you can see. 167 00:08:06.800 --> 00:08:08.900 So nothing terribly complicated up til now. 168 00:08:08.900 --> 00:08:10.500 There's a bit of data being passed from 169 00:08:10.500 --> 00:08:11.760 one place to another, 170 00:08:11.760 --> 00:08:15.330 but this is no different to what we had before really. 171 00:08:15.330 --> 00:08:17.650 If you wanted to get the average of these grades 172 00:08:17.650 --> 00:08:21.150 you would still have to pass them to a function 173 00:08:21.150 --> 00:08:24.570 called average for example and that would give you 174 00:08:24.570 --> 00:08:26.840 the average if you had the function defined. 175 00:08:26.840 --> 00:08:28.890 But using object oriented programming, 176 00:08:28.890 --> 00:08:30.970 there's one more thing you can do which is going 177 00:08:30.970 --> 00:08:33.360 to simplify your life greatly, and that is the main 178 00:08:33.360 --> 00:08:35.047 point of object oriented programming, 179 00:08:35.047 --> 00:08:38.106 which is to define another method such as 180 00:08:38.106 --> 00:08:42.450 the average method inside the class. 181 00:08:42.450 --> 00:08:47.450 And this method will take self as a parameter. 182 00:08:48.515 --> 00:08:51.660 Notice that self again doesn't have to be self, 183 00:08:51.660 --> 00:08:53.140 you can call it whatever you want. 184 00:08:53.140 --> 00:08:55.360 That's just the convention in Python, 185 00:08:55.360 --> 00:08:56.830 we usually call it self but you can call it 186 00:08:56.830 --> 00:08:57.740 whatever you want. 187 00:08:57.740 --> 00:09:00.312 So if you define a method inside a class, 188 00:09:00.312 --> 00:09:04.680 all the methods inside the class have to take a parameter 189 00:09:04.680 --> 00:09:09.223 which will be the object that was created initially. 190 00:09:10.620 --> 00:09:14.810 You can do return sum of self.grades divided by len 191 00:09:14.810 --> 00:09:16.173 of self.grades. 192 00:09:17.090 --> 00:09:22.090 Notice how this method here does not take a sequence, 193 00:09:22.860 --> 00:09:27.170 it just uses the object that was created up here. 194 00:09:27.170 --> 00:09:31.758 So how does Python know that it needs to call 195 00:09:31.758 --> 00:09:35.200 this method with this data here. 196 00:09:35.200 --> 00:09:38.270 Well here's how it works internally. 197 00:09:38.270 --> 00:09:40.710 When you create a new class, the init method 198 00:09:40.710 --> 00:09:45.710 runs and you get this new object placed in student. 199 00:09:46.061 --> 00:09:51.061 Then whenever you want to call this method here, 200 00:09:51.270 --> 00:09:56.158 all you have to do is type out student, the class, 201 00:09:56.158 --> 00:10:01.158 dot average, and then of course because this is essentially 202 00:10:01.320 --> 00:10:06.133 another function, you put in there the student object. 203 00:10:07.128 --> 00:10:12.128 And what this is doing is it's hauling the average method 204 00:10:12.140 --> 00:10:13.740 inside, that's what the dot means, 205 00:10:13.740 --> 00:10:15.380 inside the student class, 206 00:10:15.380 --> 00:10:16.940 so that's this one there. 207 00:10:16.940 --> 00:10:19.970 And the self parameter is going to take the value 208 00:10:19.970 --> 00:10:23.360 of the student variable which has that object 209 00:10:23.360 --> 00:10:25.210 that was created earlier on that contains 210 00:10:25.210 --> 00:10:27.060 the name and the grades. 211 00:10:27.060 --> 00:10:29.420 So if we save that and run it, 212 00:10:29.420 --> 00:10:31.563 you can see that you get 88.2. 213 00:10:32.850 --> 00:10:35.910 Now this is a little bit verbose, there's a few 214 00:10:35.910 --> 00:10:37.770 too many words in there, so Python has a nice bit 215 00:10:37.770 --> 00:10:40.002 of syntax that you can use instead of this one 216 00:10:40.002 --> 00:10:43.960 which is to remove the student argument 217 00:10:43.960 --> 00:10:46.400 from the average function and instead of calling 218 00:10:46.400 --> 00:10:49.500 the average method inside the class, 219 00:10:49.500 --> 00:10:52.481 call it on the object itself. 220 00:10:52.481 --> 00:10:56.370 So if you do student.average, Python is going 221 00:10:56.370 --> 00:11:01.020 to realise that student is a student object, 222 00:11:01.020 --> 00:11:03.240 so you probably want to pass it as self, 223 00:11:03.240 --> 00:11:05.090 as the first argument. 224 00:11:05.090 --> 00:11:07.360 So it will do the conversion for you, 225 00:11:07.360 --> 00:11:10.200 that is the same thing and one is the other, 226 00:11:10.200 --> 00:11:11.380 but this is a little bit shorter, 227 00:11:11.380 --> 00:11:12.680 a little bit easier to read. 228 00:11:12.680 --> 00:11:15.830 And if you name your variables well, 229 00:11:15.830 --> 00:11:18.287 then this is pretty obvious what it's gonna give you back, 230 00:11:18.287 --> 00:11:20.860 it's gonna give you the average of this student. 231 00:11:20.860 --> 00:11:24.680 Now you can make it even better, type average grade say, 232 00:11:24.680 --> 00:11:26.190 and that's going to be just a little bit 233 00:11:26.190 --> 00:11:27.580 more readable as well. 234 00:11:27.580 --> 00:11:29.510 And just to show you that this works, 235 00:11:29.510 --> 00:11:31.210 it does exactly the same thing. 236 00:11:31.210 --> 00:11:34.070 So this is the key benefit of object oriented programming. 237 00:11:34.070 --> 00:11:36.960 You can define methods inside a class 238 00:11:36.960 --> 00:11:39.880 that use the object that was initially created 239 00:11:39.880 --> 00:11:42.631 by the init method within them. 240 00:11:42.631 --> 00:11:43.960 Show that and you don't have to keep track 241 00:11:43.960 --> 00:11:45.890 of multiple different pieces of data 242 00:11:45.890 --> 00:11:50.000 and the object itself can contain these methods 243 00:11:50.000 --> 00:11:51.190 that you want to use inside it, 244 00:11:51.190 --> 00:11:55.640 so all the data and the methods are in one place 245 00:11:55.640 --> 00:11:57.078 inside the class. 246 00:11:57.078 --> 00:12:00.260 Now the init method can also take arguments 247 00:12:00.260 --> 00:12:01.700 or have parameters. 248 00:12:01.700 --> 00:12:06.340 For example, we can have a name parameter as well as self, 249 00:12:06.340 --> 00:12:09.900 so just to recap, all methods inside a class 250 00:12:09.900 --> 00:12:14.408 need to have a parameter such as self 251 00:12:14.408 --> 00:12:16.711 so they can take in the object that 252 00:12:16.711 --> 00:12:19.210 you have been constructing. 253 00:12:19.210 --> 00:12:22.330 But they can also take more arguments, 254 00:12:22.330 --> 00:12:24.630 so here we're going to have another parameter, 255 00:12:24.630 --> 00:12:27.347 the name parameter, and then you'll put the value 256 00:12:27.347 --> 00:12:30.000 of that parameter in the bracket 257 00:12:30.000 --> 00:12:32.480 of the student class call. 258 00:12:32.480 --> 00:12:36.163 So we can put here Bob, let's say. 259 00:12:36.163 --> 00:12:40.150 So now Bob will become the value for name. 260 00:12:40.150 --> 00:12:43.060 Notice that self is given for you, so you don't have 261 00:12:43.060 --> 00:12:45.420 to give it a name, this here will become 262 00:12:45.420 --> 00:12:46.633 the value for name. 263 00:12:47.760 --> 00:12:52.570 But notice that we're not using this name parameter anyway. 264 00:12:52.570 --> 00:12:56.010 We are accessing here self.name, but that's the name 265 00:12:56.010 --> 00:13:00.410 property inside self, it is not this parameter. 266 00:13:00.410 --> 00:13:02.020 If you wanted to access this parameter, 267 00:13:02.020 --> 00:13:04.160 you can do that by doing something like that. 268 00:13:04.160 --> 00:13:06.850 Self.name which is the name property inside self 269 00:13:06.850 --> 00:13:10.320 will take the value of the name variable 270 00:13:10.320 --> 00:13:13.710 inside this method which is this parameter here. 271 00:13:13.710 --> 00:13:17.818 So now if you print student.name you'll see that Bob 272 00:13:17.818 --> 00:13:21.493 will come out because that is what we defined 273 00:13:21.493 --> 00:13:23.370 in the init method. 274 00:13:23.370 --> 00:13:25.033 Let's do the same with grades. 275 00:13:26.900 --> 00:13:29.356 And now as well as name, we have to pass in 276 00:13:29.356 --> 00:13:32.420 a set of grades for the student. 277 00:13:32.420 --> 00:13:35.800 For example, we will do this one, 278 00:13:35.800 --> 00:13:37.950 give it just a little bit of a different set 279 00:13:37.950 --> 00:13:41.030 of grades there, and now we can press play 280 00:13:41.030 --> 00:13:43.950 and notice how the average grade changes. 281 00:13:43.950 --> 00:13:46.680 The average grade is now being calculated 282 00:13:46.680 --> 00:13:50.029 from this set of grades because they are stored 283 00:13:50.029 --> 00:13:54.400 in self.grades for this student. 284 00:13:54.400 --> 00:13:56.550 So when the average grade method is called 285 00:13:56.550 --> 00:13:58.510 it uses those grades. 286 00:13:58.510 --> 00:14:02.550 Remember that you can define multiple students if you want 287 00:14:02.550 --> 00:14:04.120 and that's totally fine. 288 00:14:04.120 --> 00:14:07.730 This call here in line 10 will call the init method, 289 00:14:07.730 --> 00:14:09.965 it will give you a new object, it will populate 290 00:14:09.965 --> 00:14:14.965 self.name of that object with the name argument 291 00:14:15.110 --> 00:14:19.530 and self.grades of the self object with this argument. 292 00:14:19.530 --> 00:14:22.780 And it will give you this student variable back. 293 00:14:22.780 --> 00:14:24.980 I'm gonna call this student two. 294 00:14:24.980 --> 00:14:27.670 The student two variable, exactly the same thing, 295 00:14:27.670 --> 00:14:30.600 calls the init method, passes Rolf as the name 296 00:14:30.600 --> 00:14:33.100 and it creates a new object and sets the name 297 00:14:33.100 --> 00:14:35.440 property of that new object to Rolf 298 00:14:35.440 --> 00:14:37.270 and the grades property of that new object 299 00:14:37.270 --> 00:14:39.220 to this set of grades here. 300 00:14:39.220 --> 00:14:41.410 And what you end up with are two separate 301 00:14:41.410 --> 00:14:43.240 containers of data. 302 00:14:43.240 --> 00:14:46.330 The student variable which is Bob and has these grades, 303 00:14:46.330 --> 00:14:49.242 and the student two variable which is Rolf 304 00:14:49.242 --> 00:14:50.075 and has these grades. 305 00:14:50.075 --> 00:14:52.733 So when you call student2.average_grade, 306 00:14:55.240 --> 00:14:58.973 again what Python is doing is it's calling the student class 307 00:14:58.973 --> 00:15:01.923 and passing student to there. 308 00:15:02.850 --> 00:15:05.770 So self is student two. 309 00:15:05.770 --> 00:15:08.940 When you sum the grades you're going to be summing 310 00:15:08.940 --> 00:15:11.300 these grades here because those are the grades 311 00:15:11.300 --> 00:15:14.109 that are stored inside student two. 312 00:15:14.109 --> 00:15:17.880 But of course you can still do student2.average_grade 313 00:15:17.880 --> 00:15:19.783 instead as that is a bit simpler. 314 00:15:21.110 --> 00:15:24.600 Pressing play now will give you 92.2 and 88.2 315 00:15:24.600 --> 00:15:28.440 as the two averages, one for each student. 316 00:15:28.440 --> 00:15:29.760 All right, that's everything for this video. 317 00:15:29.760 --> 00:15:31.250 I wanted to tell you a little bit about 318 00:15:31.250 --> 00:15:33.880 how object oriented programming works in Python, 319 00:15:33.880 --> 00:15:36.786 how you can define classes, how objects are created, 320 00:15:36.786 --> 00:15:40.160 and how methods work so that you can call them 321 00:15:40.160 --> 00:15:43.030 with the data in those objects. 322 00:15:43.030 --> 00:15:44.930 I hope it's all clear, but if it isn't, 323 00:15:44.930 --> 00:15:47.245 please ask a question in the course Q and A, 324 00:15:47.245 --> 00:15:48.780 we'll be more than happy to help you out. 325 00:15:48.780 --> 00:15:50.090 Thanks for joining me in this video 326 00:15:50.090 --> 00:15:51.740 and I'll see you in the next one.