1 00:00:00,000 --> 00:00:00,000 Hello guys. 2 00:00:00,000 --> 00:00:03,000 So we are going to continue the discussion with respect to Python. 3 00:00:03,000 --> 00:00:07,000 And in this video we are going to talk about the most important module that is called as oops where 4 00:00:07,000 --> 00:00:10,000 we'll be discussing about classes and objects. 5 00:00:10,000 --> 00:00:15,000 Now, object oriented programming is a programming paradigm that uses objects to design application 6 00:00:15,000 --> 00:00:17,000 and computer programs, right? 7 00:00:17,000 --> 00:00:21,000 Oops allows us for modeling real world scenarios using classes and objects. 8 00:00:21,000 --> 00:00:26,000 Now any end to end projects that you are specifically going to create, we really need to use classes. 9 00:00:26,000 --> 00:00:27,000 We need to use objects. 10 00:00:27,000 --> 00:00:30,000 This increases the reusability of the code. 11 00:00:30,000 --> 00:00:36,000 And if I talk about developing real world use cases, we will be able to use it efficiently, like we'll 12 00:00:36,000 --> 00:00:40,000 be able to develop that application efficiently with the help of classes and objects. 13 00:00:40,000 --> 00:00:45,000 Now to give you a basic example of class, let's let's see the definition of class. 14 00:00:45,000 --> 00:00:49,000 So class is nothing but it is a blueprint for creating objects okay. 15 00:00:49,000 --> 00:00:53,000 It will be having separate attributes and separate methods Okay. 16 00:00:53,000 --> 00:00:55,000 Let's say that I go ahead and create a class okay. 17 00:00:55,000 --> 00:00:59,000 So let's give a basic example over here how to create a class. 18 00:00:59,000 --> 00:01:00,000 We'll see this. 19 00:01:00,000 --> 00:01:03,000 So here we use a keyword which is called as class. 20 00:01:03,000 --> 00:01:05,000 And here we will give the class name. 21 00:01:05,000 --> 00:01:09,000 Let's say that I'm going to create a class name which is called as car okay. 22 00:01:09,000 --> 00:01:12,000 Now car is nothing but it is a class okay. 23 00:01:12,000 --> 00:01:15,000 And uh, it is a blueprint of creating objects. 24 00:01:15,000 --> 00:01:17,000 Now I'll show you how to create an object. 25 00:01:17,000 --> 00:01:21,000 Okay, so let's say that this is I'm just writing or I'm creating an empty car. 26 00:01:21,000 --> 00:01:22,000 Right? 27 00:01:22,000 --> 00:01:25,000 Now, when I say creating an object, right? 28 00:01:25,000 --> 00:01:26,000 Car may be of different type. 29 00:01:26,000 --> 00:01:28,000 It may be of different different brand. 30 00:01:28,000 --> 00:01:28,000 Right. 31 00:01:28,000 --> 00:01:29,000 So I may go ahead and create. 32 00:01:29,000 --> 00:01:32,000 Hey, uh, first of all, I'll go ahead and create an Audi object. 33 00:01:32,000 --> 00:01:33,000 Right. 34 00:01:33,000 --> 00:01:35,000 So Audi object, it is a type of car. 35 00:01:35,000 --> 00:01:38,000 So I will go ahead and use the same blueprint and create this particular object. 36 00:01:38,000 --> 00:01:39,000 Right. 37 00:01:39,000 --> 00:01:43,000 Similarly I may go ahead and take a different variety of car. 38 00:01:43,000 --> 00:01:48,000 Let's say this is BMW, and here I may again use this as an uh, or instantiate from this particular 39 00:01:48,000 --> 00:01:50,000 class, right, to create this particular object. 40 00:01:50,000 --> 00:01:51,000 So this is nothing. 41 00:01:51,000 --> 00:01:56,000 But if I go ahead and print what is the type of Audi. 42 00:01:56,000 --> 00:01:56,000 Right. 43 00:01:56,000 --> 00:02:00,000 So you will be able to see that if I execute this it is nothing. 44 00:02:00,000 --> 00:02:03,000 But it is a it is also class. 45 00:02:03,000 --> 00:02:06,000 But this is exactly an object over here, right? 46 00:02:06,000 --> 00:02:11,000 The reason why I'm saying it as an object, because we have instantiated from this specific class, 47 00:02:11,000 --> 00:02:12,000 which is called as car. 48 00:02:12,000 --> 00:02:13,000 Okay. 49 00:02:13,000 --> 00:02:16,000 And similarly, uh, you can just imagine, right. 50 00:02:16,000 --> 00:02:18,000 What class is it is a real world entity. 51 00:02:18,000 --> 00:02:18,000 Okay. 52 00:02:18,000 --> 00:02:21,000 And it is also called as a blueprint. 53 00:02:21,000 --> 00:02:27,000 And just by using this specific class car, I can create different objects which may be using the features 54 00:02:27,000 --> 00:02:28,000 of this specific car. 55 00:02:28,000 --> 00:02:28,000 Right. 56 00:02:28,000 --> 00:02:30,000 Like we have Audi, BMW and all. 57 00:02:30,000 --> 00:02:31,000 Okay. 58 00:02:31,000 --> 00:02:38,000 Now, uh, let me just go ahead and probably explain more about it because I have not still, uh, discussed 59 00:02:38,000 --> 00:02:44,000 about attributes and methods, which we also called it as instance variable or instance methods. 60 00:02:44,000 --> 00:02:45,000 Okay. 61 00:02:45,000 --> 00:02:48,000 So if I probably also go ahead and print this Audi. 62 00:02:48,000 --> 00:02:50,000 So if I go ahead and print Audi what will I get. 63 00:02:50,000 --> 00:02:56,000 It will be showing that hey this is a car object at this specific memory location, okay? 64 00:02:56,000 --> 00:02:59,000 And similarly, if I go ahead and go ahead and print BMW. 65 00:02:59,000 --> 00:03:00,000 Right. 66 00:03:00,000 --> 00:03:05,000 So here also you'll be able to see, yes, it is showing that yes, it is a car object at this specific 67 00:03:05,000 --> 00:03:06,000 memory location. 68 00:03:06,000 --> 00:03:07,000 Right now. 69 00:03:07,000 --> 00:03:10,000 Let me just go ahead and include two more important things. 70 00:03:10,000 --> 00:03:15,000 Let's say I will go ahead and write instance variable and methods okay. 71 00:03:15,000 --> 00:03:15,000 Okay. 72 00:03:16,000 --> 00:03:17,000 Methods. 73 00:03:18,000 --> 00:03:20,000 Now let me just take another class. 74 00:03:20,000 --> 00:03:20,000 Okay. 75 00:03:20,000 --> 00:03:23,000 Let's say that I'm going to create a class called as dog. 76 00:03:23,000 --> 00:03:24,000 Right. 77 00:03:24,000 --> 00:03:26,000 Now dog is a blueprint right. 78 00:03:26,000 --> 00:03:30,000 And in order to define the attributes over here. 79 00:03:30,000 --> 00:03:30,000 Right. 80 00:03:30,000 --> 00:03:33,000 See uh, one way, if I probably take this already and. 81 00:03:33,000 --> 00:03:39,000 All right, if I just go ahead and write ord dot, let's say I want to go ahead and define one instance 82 00:03:39,000 --> 00:03:42,000 variable that is present inside the class. 83 00:03:42,000 --> 00:03:44,000 Let's say Audi has some windows right? 84 00:03:44,000 --> 00:03:47,000 I will just go ahead and write for write. 85 00:03:47,000 --> 00:03:49,000 This windows is basically for right. 86 00:03:49,000 --> 00:03:57,000 And if I go ahead and print Audi dot windows, then I will be able to see that I am able to get the 87 00:03:57,000 --> 00:03:57,000 answer. 88 00:03:57,000 --> 00:04:04,000 As for so, windows is a kind of attribute that is present inside the car, and for Audi it may be that 89 00:04:04,000 --> 00:04:07,000 I may have four windows for some other car. 90 00:04:07,000 --> 00:04:08,000 I may just have two windows. 91 00:04:08,000 --> 00:04:13,000 Like, let's say that I'm taking a very smaller car over there, which is just like a Tata Nano. 92 00:04:13,000 --> 00:04:17,000 Okay, it may be having four windows, but let's say that there is a new variety of car that may have 93 00:04:17,000 --> 00:04:18,000 two windows. 94 00:04:18,000 --> 00:04:20,000 So I can change that particular attribute values. 95 00:04:20,000 --> 00:04:23,000 And this is how we specifically define right. 96 00:04:23,000 --> 00:04:23,000 This is nothing. 97 00:04:23,000 --> 00:04:25,000 But this is a kind of attributes. 98 00:04:25,000 --> 00:04:31,000 But initializing attributes like this is not a proper way. 99 00:04:31,000 --> 00:04:34,000 The reason is very much simple why this is not a proper way. 100 00:04:34,000 --> 00:04:38,000 Because see, whenever I create another object, let's say that I'm going to create another object. 101 00:04:38,000 --> 00:04:40,000 Let's say this will be a Tata car. 102 00:04:40,000 --> 00:04:43,000 And now I will go ahead and initialize with car object. 103 00:04:43,000 --> 00:04:43,000 Right. 104 00:04:43,000 --> 00:04:45,000 I'll go ahead and create this particular object. 105 00:04:45,000 --> 00:04:48,000 Now I may go ahead and write Tata dot doors. 106 00:04:48,000 --> 00:04:48,000 Right. 107 00:04:48,000 --> 00:04:50,000 So this will be my another attribute. 108 00:04:50,000 --> 00:04:53,000 And let's say they are around five four doors over here Right? 109 00:04:53,000 --> 00:04:59,000 But if you see with respect to Audi, I did not created a attribute called a doors. 110 00:04:59,000 --> 00:05:03,000 Whereas over here I created something called as windows in that I did not create an attribute called 111 00:05:03,000 --> 00:05:04,000 as windows. 112 00:05:04,000 --> 00:05:04,000 Right. 113 00:05:04,000 --> 00:05:08,000 So if I go ahead and print tata dot windows, will I get anything. 114 00:05:08,000 --> 00:05:09,000 Let's see. 115 00:05:09,000 --> 00:05:15,000 So here you can see that I'll be getting an error saying that the car object has no attribute windows. 116 00:05:15,000 --> 00:05:15,000 Right. 117 00:05:15,000 --> 00:05:19,000 So defining the attributes in this way is not a proper way. 118 00:05:19,000 --> 00:05:25,000 So I will just show you another way how we can clearly define all the attributes and methods in the 119 00:05:25,000 --> 00:05:29,000 first hand while we are initializing, or while we are creating the objects itself. 120 00:05:29,000 --> 00:05:30,000 Right. 121 00:05:30,000 --> 00:05:33,000 So I'm going to take an example with respect to dog. 122 00:05:33,000 --> 00:05:33,000 Okay. 123 00:05:33,000 --> 00:05:37,000 And here uh, there is one very important function. 124 00:05:37,000 --> 00:05:44,000 See if I go ahead and write dir Directory of this specific class that is called a starter. 125 00:05:44,000 --> 00:05:45,000 Okay. 126 00:05:45,000 --> 00:05:50,000 Here you'll be seeing there will be a lot of different different inbuilt methods right. 127 00:05:50,000 --> 00:05:54,000 And each and every inbuilt methods will be doing something else right now. 128 00:05:54,000 --> 00:05:58,000 Since you can see that I have created an attribute called as doors, you will be also able to see that 129 00:05:58,000 --> 00:06:01,000 this doors will be available over here. 130 00:06:01,000 --> 00:06:04,000 Right inside this particular directory I will be talking about different. 131 00:06:04,000 --> 00:06:07,000 Different uh, over here methods. 132 00:06:07,000 --> 00:06:07,000 Right. 133 00:06:07,000 --> 00:06:09,000 What functionalities it usually does. 134 00:06:09,000 --> 00:06:14,000 But here I'm going to take about I'm going to talk about one method which is called as underscore underscore 135 00:06:14,000 --> 00:06:15,000 init underscore underscore. 136 00:06:15,000 --> 00:06:23,000 Now what this method is all about this method is called as constructor okay constructor. 137 00:06:23,000 --> 00:06:25,000 Now what does this specific method do. 138 00:06:25,000 --> 00:06:30,000 So if I go ahead and write definition underscore underscore init underscore underscore. 139 00:06:30,000 --> 00:06:36,000 If initially I want to define any attributes, I can make sure that with the help of this particular 140 00:06:36,000 --> 00:06:39,000 constructor at the first hand, I'll be defining. 141 00:06:39,000 --> 00:06:43,000 I'll be able to define all the attributes that will be available inside this particular class. 142 00:06:43,000 --> 00:06:47,000 Right now, in order to define it, let's say in dog. 143 00:06:47,000 --> 00:06:47,000 Right. 144 00:06:47,000 --> 00:06:50,000 Um, let's say I have two attributes over here. 145 00:06:50,000 --> 00:06:53,000 One is name and the other one is age. 146 00:06:53,000 --> 00:06:53,000 Right. 147 00:06:53,000 --> 00:06:59,000 So while I'm initializing, or while I am creating the object from a dog class, I have to make sure 148 00:06:59,000 --> 00:07:01,000 that I have to give this two attributes. 149 00:07:01,000 --> 00:07:02,000 Okay. 150 00:07:02,000 --> 00:07:06,000 During the runtime, I have to give this two values during the runtime when I create the object. 151 00:07:06,000 --> 00:07:12,000 Okay, now the best thing over here is that this is basically my parameter, right? 152 00:07:12,000 --> 00:07:17,000 And internally I will go ahead and create some instance variable. 153 00:07:17,000 --> 00:07:22,000 Now this instance variable are like some kind of properties that are available inside the dog class 154 00:07:22,000 --> 00:07:23,000 okay. 155 00:07:23,000 --> 00:07:29,000 And you know that I have to basically take this particular name and assign this name itself, because 156 00:07:29,000 --> 00:07:32,000 during the runtime I'm going to put this particular value. 157 00:07:32,000 --> 00:07:35,000 Now obviously I have written the same name. 158 00:07:35,000 --> 00:07:37,000 The variable name is almost same. 159 00:07:37,000 --> 00:07:41,000 So let me just go ahead and write one more parameter which is called as self okay. 160 00:07:41,000 --> 00:07:42,000 It is not compulsory. 161 00:07:42,000 --> 00:07:44,000 You always need to write self okay. 162 00:07:44,000 --> 00:07:46,000 You can write anything over here. 163 00:07:46,000 --> 00:07:46,000 You can write crush. 164 00:07:46,000 --> 00:07:48,000 You can write your name also. 165 00:07:48,000 --> 00:07:55,000 But self uh is a keyword which we specifically use, you know worldwide in terms of good practices we 166 00:07:55,000 --> 00:07:56,000 use self keyword. 167 00:07:56,000 --> 00:07:59,000 Right now this self keyword will be responsible. 168 00:07:59,000 --> 00:08:05,000 You know, in probably accessing the instance variable inside the class itself whenever we create an 169 00:08:05,000 --> 00:08:06,000 object. 170 00:08:06,000 --> 00:08:09,000 So here what I'm going to write I'm just going to say self dot name. 171 00:08:09,000 --> 00:08:15,000 Now this name that you will be seeing which is which is along with self dot name. 172 00:08:15,000 --> 00:08:19,000 This name is nothing, but it is my instance variable that is available inside the dog class. 173 00:08:19,000 --> 00:08:20,000 Okay. 174 00:08:20,000 --> 00:08:25,000 And this name is what is the parameter that I'm passing while creating the object? 175 00:08:25,000 --> 00:08:27,000 Okay, so here there are two parameters. 176 00:08:27,000 --> 00:08:31,000 One is self dot name and the second one that I'm actually going to go ahead and write. 177 00:08:31,000 --> 00:08:32,000 It is nothing but self dot. 178 00:08:33,000 --> 00:08:35,000 Uh age is equal to age. 179 00:08:35,000 --> 00:08:41,000 So this way I am initializing my entire class with a constructor. 180 00:08:41,000 --> 00:08:47,000 Now if I go ahead and create the object okay, now let's go ahead and create the objects right. 181 00:08:47,000 --> 00:08:50,000 You will be able to see that as soon as I go ahead and write. 182 00:08:50,000 --> 00:08:52,000 Hey, let's go ahead and create my object. 183 00:08:52,000 --> 00:08:52,000 Dog one. 184 00:08:52,000 --> 00:08:56,000 This will get initialized from dog okay. 185 00:08:56,000 --> 00:08:58,000 And here I'm going to give two parameters. 186 00:08:58,000 --> 00:09:02,000 If I execute like this it will tell me hey you're missing two required positional argument name and 187 00:09:02,000 --> 00:09:03,000 age. 188 00:09:03,000 --> 00:09:05,000 Because name and age is not given. 189 00:09:05,000 --> 00:09:10,000 As soon as I call this, what is internally going to happen is that it is going to call this constructor 190 00:09:10,000 --> 00:09:11,000 first. 191 00:09:11,000 --> 00:09:12,000 Okay? 192 00:09:12,000 --> 00:09:16,000 Because of this constructor, it is going to take all these values that is required for the instance 193 00:09:16,000 --> 00:09:16,000 variable. 194 00:09:16,000 --> 00:09:18,000 So here I need to provide two parameter. 195 00:09:18,000 --> 00:09:21,000 Let's say here I will go ahead and write buddy. 196 00:09:21,000 --> 00:09:23,000 And the age is three okay. 197 00:09:23,000 --> 00:09:28,000 Now if I go ahead and execute this print dog one okay. 198 00:09:28,000 --> 00:09:33,000 You will be able to see that I will be able to create a dog object at this specific memory location. 199 00:09:34,000 --> 00:09:37,000 Now this instance variable is their right name and age. 200 00:09:37,000 --> 00:09:51,000 Now let's go ahead and retrieve this dog One dot name and the next one is print dog one dot age. 201 00:09:51,000 --> 00:09:51,000 Right. 202 00:09:51,000 --> 00:09:56,000 So now if I go ahead and access this values, you'll be able to see that I'm able to get that value 203 00:09:56,000 --> 00:09:57,000 which is called as buddy and three. 204 00:09:57,000 --> 00:09:58,000 Right. 205 00:09:58,000 --> 00:10:01,000 Similarly, I can go ahead and create any number of dogs objects. 206 00:10:01,000 --> 00:10:01,000 Right. 207 00:10:01,000 --> 00:10:03,000 So I'll go ahead and write dog two. 208 00:10:03,000 --> 00:10:07,000 And again I will be using dog and I will go and give my parameters over here. 209 00:10:07,000 --> 00:10:11,000 Let's say I will give something like Lucy and the age is four. 210 00:10:11,000 --> 00:10:14,000 And I will be able to print the same thing over here. 211 00:10:14,000 --> 00:10:24,000 That is nothing but dog two dot name and similarly print dog to dot age, right? 212 00:10:24,000 --> 00:10:30,000 So here you will be able to see that I will be able to access this instance variable over here Now the 213 00:10:30,000 --> 00:10:37,000 best thing is that we have defined the instance variable initially in the constructor so that we cannot 214 00:10:37,000 --> 00:10:42,000 create any more, you know, whatever things is defined in the constructor, only those number of instance 215 00:10:42,000 --> 00:10:43,000 variable itself we can create. 216 00:10:43,000 --> 00:10:49,000 If tomorrow I require any more instance variable, I can just go ahead and write self dot that particular 217 00:10:49,000 --> 00:10:50,000 instance variable. 218 00:10:50,000 --> 00:10:53,000 And I'll assign the value based on the parameter that I pass over here. 219 00:10:53,000 --> 00:10:54,000 Right. 220 00:10:54,000 --> 00:10:59,000 So this is the best practice that we specifically use with respect to creating instance variables right. 221 00:10:59,000 --> 00:11:06,000 Now let's talk about instance method right now instance variable whenever we talk about it is some kind 222 00:11:06,000 --> 00:11:07,000 of properties. 223 00:11:07,000 --> 00:11:10,000 That dog that talks about dog right. 224 00:11:10,000 --> 00:11:14,000 So over here name and age are just like my properties for this particular dog. 225 00:11:14,000 --> 00:11:15,000 Right. 226 00:11:15,000 --> 00:11:16,000 It's ah these are nothing. 227 00:11:16,000 --> 00:11:18,000 But these are some kind of attributes. 228 00:11:18,000 --> 00:11:18,000 Right. 229 00:11:18,000 --> 00:11:24,000 Similarly, they may be methods which we also call this as instance methods like a dog may be barking. 230 00:11:24,000 --> 00:11:24,000 Right. 231 00:11:24,000 --> 00:11:26,000 It may be doing some kind of functionalities. 232 00:11:26,000 --> 00:11:27,000 Right. 233 00:11:27,000 --> 00:11:29,000 It may be running at a specific speed something. 234 00:11:29,000 --> 00:11:29,000 Right. 235 00:11:29,000 --> 00:11:30,000 So those are nothing. 236 00:11:30,000 --> 00:11:32,000 But those are basically instance method. 237 00:11:32,000 --> 00:11:37,000 Now let me show you how you can actually go ahead and create the instance methods. 238 00:11:37,000 --> 00:11:37,000 Right. 239 00:11:37,000 --> 00:11:40,000 So now I'm going to define a class with an instance method. 240 00:11:40,000 --> 00:11:46,000 So let's go ahead and define a class with instance methods okay. 241 00:11:46,000 --> 00:11:50,000 Now in order to define a class with instance method again I will go ahead and write class dog. 242 00:11:50,000 --> 00:11:51,000 Okay. 243 00:11:51,000 --> 00:11:56,000 Now as you know that I will be using my init constructor. 244 00:11:56,000 --> 00:12:00,000 So I will go ahead and write definition underscore underscore init underscore underscore. 245 00:12:00,000 --> 00:12:02,000 Here I will use a self keyword. 246 00:12:02,000 --> 00:12:05,000 Let's say that there are two parameters or two features that I'm going to use. 247 00:12:05,000 --> 00:12:06,000 That is name and age. 248 00:12:06,000 --> 00:12:08,000 These are my two instance variable. 249 00:12:08,000 --> 00:12:13,000 I can also say it as properties, attributes, anything you can specifically talk about. 250 00:12:13,000 --> 00:12:17,000 But all these parameters are basically talking about this dog class itself, right? 251 00:12:17,000 --> 00:12:19,000 These are the properties of them. 252 00:12:19,000 --> 00:12:19,000 Right. 253 00:12:19,000 --> 00:12:21,000 And this is what I'm going to pass in the runtime. 254 00:12:21,000 --> 00:12:23,000 Now I'll go ahead and create my properties. 255 00:12:23,000 --> 00:12:26,000 So I'll go ahead and write self dot name is equal to name. 256 00:12:26,000 --> 00:12:31,000 Then I'm going to write self dot age is equal to age Okay, now this is fine. 257 00:12:31,000 --> 00:12:34,000 Right now once I create my constructor. 258 00:12:34,000 --> 00:12:38,000 Now I'm going to write create some instance method that is related to dog. 259 00:12:38,000 --> 00:12:41,000 Let's say the dog will be barking right. 260 00:12:41,000 --> 00:12:45,000 So and different different dog can bark in a different different way. 261 00:12:45,000 --> 00:12:47,000 So here also I'll be using the self keyword. 262 00:12:47,000 --> 00:12:48,000 The reason is very simple. 263 00:12:48,000 --> 00:12:52,000 So that inside this method also I will be able to use this instance variable okay. 264 00:12:52,000 --> 00:12:55,000 That is the reason we provide this self keyword over here. 265 00:12:55,000 --> 00:13:02,000 Now I will go ahead and write print okay some functionality or some uh, some print statement. 266 00:13:02,000 --> 00:13:07,000 I will write over here and I'll go ahead and write self dot name right self dot name basically means 267 00:13:07,000 --> 00:13:08,000 the same attribute. 268 00:13:08,000 --> 00:13:12,000 I'm calling it over here says woof. 269 00:13:12,000 --> 00:13:12,000 Right. 270 00:13:12,000 --> 00:13:16,000 So this is the sound uh, specific dog makes uh in generic. 271 00:13:16,000 --> 00:13:17,000 Okay. 272 00:13:17,000 --> 00:13:18,000 So here you can actually see over here. 273 00:13:18,000 --> 00:13:19,000 Right. 274 00:13:19,000 --> 00:13:25,000 And uh, if I probably, uh, just consider this, this is one of the instance method. 275 00:13:25,000 --> 00:13:26,000 Okay. 276 00:13:26,000 --> 00:13:28,000 Now what I'm going to do I'll go ahead and create my object. 277 00:13:28,000 --> 00:13:30,000 Let's say that this is my dog one. 278 00:13:30,000 --> 00:13:33,000 And here I'm just going to call dog. 279 00:13:34,000 --> 00:13:37,000 And let me just give the values here I will be giving buddy. 280 00:13:37,000 --> 00:13:39,000 Comma three is the age. 281 00:13:39,000 --> 00:13:46,000 Now I can use this object and call this particular function right method right. 282 00:13:46,000 --> 00:13:49,000 This method is nothing, but it is basically called as bark. 283 00:13:49,000 --> 00:13:55,000 Okay, now if I go ahead and just execute this, you'll be able to see that I will be getting that print 284 00:13:55,000 --> 00:13:57,000 says buddy says HUF right. 285 00:13:57,000 --> 00:14:00,000 Now tomorrow I want to go ahead and create my another dog two. 286 00:14:00,000 --> 00:14:01,000 Okay. 287 00:14:01,000 --> 00:14:07,000 And let's say this dog two is basically having the name as Lucy, okay. 288 00:14:07,000 --> 00:14:09,000 And the age is four, right. 289 00:14:09,000 --> 00:14:13,000 If I go ahead and just go ahead and call this dog two dot bark. 290 00:14:13,000 --> 00:14:18,000 So here you will be able to see that I'll be able to see it get Lucy says woof right. 291 00:14:18,000 --> 00:14:19,000 So buddy says woof. 292 00:14:19,000 --> 00:14:20,000 Lucy says woof. 293 00:14:20,000 --> 00:14:22,000 Now this is the function. 294 00:14:22,000 --> 00:14:27,000 And based on different different dog types, you can just consider that the object is nothing but different, 295 00:14:27,000 --> 00:14:29,000 different dog types, right? 296 00:14:29,000 --> 00:14:33,000 They're using the same properties and they're using the same method. 297 00:14:33,000 --> 00:14:36,000 And this will be relative to that specific object. 298 00:14:36,000 --> 00:14:42,000 So that is the reason over here in the definition we have clearly written as a class is a blueprint 299 00:14:42,000 --> 00:14:43,000 for creating objects. 300 00:14:43,000 --> 00:14:47,000 And it has its own attribute and methods which can be used by this objects. 301 00:14:47,000 --> 00:14:48,000 Right. 302 00:14:48,000 --> 00:14:53,000 So I hope you got an idea with respect to this, and I hope you are able to understand this. 303 00:14:53,000 --> 00:14:53,000 Okay. 304 00:14:54,000 --> 00:14:58,000 Now, uh, let's design a better example for you. 305 00:14:58,000 --> 00:14:59,000 Okay. 306 00:14:59,000 --> 00:15:04,000 So here we are going to take this example which is called as modeling. 307 00:15:06,000 --> 00:15:11,000 Modeling a bank account okay. 308 00:15:11,000 --> 00:15:13,000 So now let's go ahead and do this okay. 309 00:15:13,000 --> 00:15:20,000 So here you'll be able to see I will define a class for bank account. 310 00:15:20,000 --> 00:15:20,000 Okay. 311 00:15:20,000 --> 00:15:24,000 First of all, now you know in a bank account you will be able to withdraw money, you will be able 312 00:15:24,000 --> 00:15:25,000 to deposit money. 313 00:15:25,000 --> 00:15:28,000 And you will be also able to see the balance in the money. 314 00:15:28,000 --> 00:15:28,000 Right. 315 00:15:28,000 --> 00:15:32,000 So here, first of all, how do we design this entire application with the help of classes. 316 00:15:32,000 --> 00:15:37,000 So I'm just going to use class with respect to bank account okay. 317 00:15:37,000 --> 00:15:41,000 It is always a good practice that you use capital letter whenever you are defining a class. 318 00:15:41,000 --> 00:15:44,000 Then I'm going to use my constructor. 319 00:15:44,000 --> 00:15:47,000 That is underscore underscore init underscore underscore. 320 00:15:47,000 --> 00:15:50,000 Let's say that what all parameters I'm going to probably give over here. 321 00:15:50,000 --> 00:15:54,000 One is owner information and the next is balance. 322 00:15:54,000 --> 00:15:58,000 By default whenever we create an account the balance will be zero okay. 323 00:15:58,000 --> 00:16:01,000 So by default I'm giving some values over here. 324 00:16:01,000 --> 00:16:05,000 Then I will go ahead and write self dot owner is equal to owner. 325 00:16:05,000 --> 00:16:12,000 So and again guys you may be thinking should this particular attribute be same to this particular parameter 326 00:16:12,000 --> 00:16:12,000 name? 327 00:16:12,000 --> 00:16:13,000 The answer is no right? 328 00:16:13,000 --> 00:16:19,000 You can write as your own, but I'm just following the good practices that many of the developer usually 329 00:16:19,000 --> 00:16:19,000 follows. 330 00:16:19,000 --> 00:16:21,000 Then I'll go ahead and write. 331 00:16:21,000 --> 00:16:24,000 Self dot balance is equal to balance. 332 00:16:24,000 --> 00:16:27,000 Okay, now here you can see that I have created my bank account. 333 00:16:27,000 --> 00:16:28,000 Perfect. 334 00:16:28,000 --> 00:16:30,000 These are my attributes right? 335 00:16:30,000 --> 00:16:31,000 Owner and balance. 336 00:16:31,000 --> 00:16:33,000 We also call this as instance variable. 337 00:16:33,000 --> 00:16:37,000 Now the next thing is that I will go ahead and define my instance method. 338 00:16:37,000 --> 00:16:41,000 So first of all we'll go and create one method which is called as deposit. 339 00:16:41,000 --> 00:16:43,000 And here I'm going to give self. 340 00:16:43,000 --> 00:16:46,000 And one parameter that I will give is amount okay. 341 00:16:46,000 --> 00:16:51,000 Amount is like how much we really need to deposit as the parameter I'm giving okay. 342 00:16:51,000 --> 00:16:59,000 Now whenever I try to add money in my account through deposit, I have to probably increase my balance 343 00:16:59,000 --> 00:17:03,000 now in order to get the excess of the balance again, I have to use self dot balance. 344 00:17:03,000 --> 00:17:07,000 Keyword plus is equal to this specific amount, right? 345 00:17:07,000 --> 00:17:12,000 And this is what we are basically doing with respect to the balance deposit function. 346 00:17:12,000 --> 00:17:15,000 And I will just go ahead and print and go ahead and write. 347 00:17:15,000 --> 00:17:24,000 Hey uh amount is deposited, new balances. 348 00:17:24,000 --> 00:17:26,000 I'm just going to write some print statement. 349 00:17:26,000 --> 00:17:29,000 New balances, self dot balance okay. 350 00:17:29,000 --> 00:17:33,000 Self dot balance I cannot directly use balance because this is nothing. 351 00:17:33,000 --> 00:17:36,000 But it is an instance variable that is available over here okay. 352 00:17:36,000 --> 00:17:40,000 Now the next function that I'm actually going to create is nothing but withdraw. 353 00:17:40,000 --> 00:17:43,000 So I'm going to write withdraw, definition withdraw. 354 00:17:43,000 --> 00:17:47,000 And here I'm going to use self comma amount okay. 355 00:17:47,000 --> 00:17:57,000 And with respect to this if amount is greater than self dot balance okay I'm just saying that hey if 356 00:17:57,000 --> 00:18:01,000 I'm withdrawing, first of all I need to check whether the amount is greater than self dot balance. 357 00:18:01,000 --> 00:18:05,000 If the amount is greater than self dot balance. 358 00:18:05,000 --> 00:18:09,000 And if I am trying to withdraw, then obviously this should not be allowed. 359 00:18:09,000 --> 00:18:10,000 And I'll just go ahead and print. 360 00:18:10,000 --> 00:18:11,000 Hey. 361 00:18:11,000 --> 00:18:12,000 Insufficient funds. 362 00:18:13,000 --> 00:18:15,000 Insufficient funds. 363 00:18:15,000 --> 00:18:16,000 Okay. 364 00:18:16,000 --> 00:18:20,000 And finally I'll close this right now. 365 00:18:20,000 --> 00:18:25,000 If this is not satisfied, then what I will do, I'll go ahead and write my else condition. 366 00:18:25,000 --> 00:18:29,000 And this time I have to subtract it from my balance account. 367 00:18:29,000 --> 00:18:33,000 So I will go ahead and write minus equal to this specific amount. 368 00:18:33,000 --> 00:18:35,000 Okay, so I hope you are able to understand this. 369 00:18:35,000 --> 00:18:41,000 Now if the amount is greater than self dot balance I will say hey, it is insufficient funds. 370 00:18:41,000 --> 00:18:47,000 But if this is not true, if the amount is less than self dot balance, I should be able to withdraw 371 00:18:47,000 --> 00:18:47,000 it. 372 00:18:47,000 --> 00:18:52,000 So here you will be able to see that I am writing self dot balance minus is equal to that specific amount. 373 00:18:52,000 --> 00:19:02,000 And here I will go ahead and print and say that by using an f string say that hey this amount is withdrawn. 374 00:19:04,000 --> 00:19:06,000 Withdrawn okay. 375 00:19:06,000 --> 00:19:07,000 New balance. 376 00:19:09,000 --> 00:19:14,000 New balance is self dot balance right. 377 00:19:15,000 --> 00:19:16,000 So this is perfect. 378 00:19:16,000 --> 00:19:20,000 So I've created two instance method along with that two instance variable. 379 00:19:20,000 --> 00:19:22,000 And finally one more method I will go ahead and create. 380 00:19:22,000 --> 00:19:24,000 And you can create any number of methods. 381 00:19:24,000 --> 00:19:26,000 I will say hey get balance okay. 382 00:19:26,000 --> 00:19:28,000 And here I will again use the self keyword. 383 00:19:28,000 --> 00:19:34,000 And all we have to do over here is that I will just go ahead and write return self dot balance. 384 00:19:34,000 --> 00:19:37,000 I just need to return the balance in my account. 385 00:19:37,000 --> 00:19:38,000 Okay, done. 386 00:19:40,000 --> 00:19:43,000 Now you'll be able to see the balance amount and all. 387 00:19:43,000 --> 00:19:44,000 Everything is there. 388 00:19:44,000 --> 00:19:46,000 Now let's go ahead and create an object. 389 00:19:46,000 --> 00:19:48,000 So I will go ahead and create an object. 390 00:19:48,000 --> 00:19:51,000 Now you can perform any kind of operation that you really want. 391 00:19:51,000 --> 00:19:55,000 So while creating an object I have to make sure that I create an account. 392 00:19:55,000 --> 00:19:59,000 So first of all I will go ahead and write bank account okay which is my class. 393 00:19:59,000 --> 00:20:05,000 And when I call this particular bank account I have to give two attributes that is owner and balance. 394 00:20:05,000 --> 00:20:07,000 Write owner over here is nothing. 395 00:20:07,000 --> 00:20:09,000 But I'll go ahead and say crush. 396 00:20:09,000 --> 00:20:15,000 And initially let's say my balance is I am depositing around ₹500 okay. 397 00:20:15,000 --> 00:20:17,000 Or let's say ₹5,000. 398 00:20:17,000 --> 00:20:17,000 Okay. 399 00:20:17,000 --> 00:20:24,000 Now let me just go ahead and print the count dot balance. 400 00:20:24,000 --> 00:20:25,000 So this is crush account right. 401 00:20:25,000 --> 00:20:28,000 So here we'll be able to see that I'm getting ₹5,000. 402 00:20:28,000 --> 00:20:34,000 Now let's say that I want to call this instance method okay. 403 00:20:34,000 --> 00:20:35,000 Where I want to withdraw some money. 404 00:20:35,000 --> 00:20:36,000 Okay. 405 00:20:36,000 --> 00:20:38,000 So first of all let's go ahead and do some deposit. 406 00:20:38,000 --> 00:20:42,000 Let's say that I got my salary and my salary is ₹100. 407 00:20:42,000 --> 00:20:44,000 And I've deposited it okay. 408 00:20:44,000 --> 00:20:49,000 So if I go ahead and print or if I just go ahead and execute this, you'll be able to see that I'm getting 409 00:20:49,000 --> 00:20:54,000 a message saying that, hey, 100 is deposited, new balance is 5100 right now. 410 00:20:54,000 --> 00:20:57,000 Let me just go ahead and withdraw some money. 411 00:20:57,000 --> 00:21:04,000 Let's say that I want to withdraw account dot withdraw is nothing, but I want to withdraw ₹300. 412 00:21:04,000 --> 00:21:06,000 So I'll just go ahead and execute it. 413 00:21:06,000 --> 00:21:07,000 Now here you can see. 414 00:21:07,000 --> 00:21:09,000 Hey, 300 is withdrawn. 415 00:21:09,000 --> 00:21:12,000 New balance is 4800 right now. 416 00:21:12,000 --> 00:21:18,000 Finally, if I want to get the complete account balance, I should be able to just call print account 417 00:21:18,000 --> 00:21:20,000 dot get balance. 418 00:21:20,000 --> 00:21:22,000 And that is what I'm actually going to execute it. 419 00:21:22,000 --> 00:21:24,000 And here you can see I'm getting 4800. 420 00:21:24,000 --> 00:21:31,000 So here in just front of you I have designed the entire bank account with respect to all the operations 421 00:21:31,000 --> 00:21:36,000 with the help of class, instance variable and instance method. 422 00:21:36,000 --> 00:21:41,000 So I hope you are able to understand this, uh, completely with respect to this particular example 423 00:21:41,000 --> 00:21:43,000 of bank account and all. 424 00:21:43,000 --> 00:21:47,000 Um, as we go ahead, we'll be talking more about different, different examples, right. 425 00:21:47,000 --> 00:21:51,000 This is just to give you an idea of how powerful this class is. 426 00:21:51,000 --> 00:21:55,000 Ah, but please make sure that always make sure you keep a note of all the indentation. 427 00:21:55,000 --> 00:21:56,000 How to probably create it. 428 00:21:57,000 --> 00:22:01,000 Uh, you need to understand very much clearly that this init is nothing, but it is a constructor. 429 00:22:01,000 --> 00:22:02,000 This. 430 00:22:02,000 --> 00:22:04,000 Ah, my instance variable. 431 00:22:04,000 --> 00:22:09,000 This is ah, my instance methods and I can probably go ahead and write any number of instance method 432 00:22:09,000 --> 00:22:10,000 that I want. 433 00:22:10,000 --> 00:22:15,000 And the importance of self keyword is to use this kind of instance variable wherever we want. 434 00:22:15,000 --> 00:22:20,000 Inside this particular instance method, right out of this class, I cannot use self keyword. 435 00:22:20,000 --> 00:22:22,000 That is very much clear, right? 436 00:22:22,000 --> 00:22:26,000 So I hope you are able to understand this, uh, entire video. 437 00:22:26,000 --> 00:22:31,000 So finally I will just write some conclusion saying that What? 438 00:22:31,000 --> 00:22:32,000 All things. 439 00:22:32,000 --> 00:22:36,000 Uh, is important with respect to why this class is are important. 440 00:22:36,000 --> 00:22:39,000 So here object oriented programming is very, very much important. 441 00:22:39,000 --> 00:22:43,000 It allows you to model real world scenarios using class an object. 442 00:22:43,000 --> 00:22:47,000 In this lesson you learn how to create a class in objects, define instance variable and method and 443 00:22:47,000 --> 00:22:49,000 use them to perform various operation. 444 00:22:49,000 --> 00:22:50,000 Right? 445 00:22:50,000 --> 00:22:52,000 So yes, this was it for my side. 446 00:22:52,000 --> 00:22:53,000 I hope you liked this particular video. 447 00:22:53,000 --> 00:22:55,000 I will see you all in the next video. 448 00:22:55,000 --> 00:22:55,000 Thank you.