Methods

If all we could do with classes is set and 0:00 use attributes, they wouldn't be all that useful, would they? 0:02 Like I mentioned before, though, 0:04 we can give verbs to our objects by creating methods. 0:05 Now, don't get too worried about methods, cuz I'll let you in on a secret. 0:08 Methods are just functions that belong to a class. 0:11 So, if you can write a function, you can write a method. 0:13 They do have one little gotcha, though. 0:16 So, let's get into Workspaces so I can teach you all about them. 0:17 So, I'm gonna simplify things a little bit, 0:20 I'm gonna leave out a couple of things here at first. 0:22 Methods in classes are the actions of the instances of your class can do. 0:24 For example, my Thief class might have a pickpocket method that lets it try and 0:29 snatch something out of another person's pocket. 0:33 Methods belong to the class, so they're indented inside of it, 0:36 just like attributes are. 0:39 So, we'll say def pickpocket and that'll take an argument self and 0:40 then we'll return a bool of random.randit between 0 and 1. 0:41 And that means I 0:41 need to import random. 0:46 So, what's this self thing that's going on here? 0:57 What's that about? 1:01 Well, methods are functions that's belong to a class. 1:02 Whenever they're used, 1:05 however, they're used by an instance, not by the actual class. 1:06 Because of that, methods always take at least one parameter, 1:11 which represents the instance that's using the method. 1:14 Now, by convention that parameter's always called self, but 1:17 you can call it anything you want in your own classes. 1:21 But I highly recommend you stick with self. 1:23 Now, the neat thing here is you don't give any arguments to self 1:26 when you use the method. 1:29 Let's try this out down here in our console. 1:31 So, Python from characters import Thief. 1:33 And kenneth = Thief just like before, right? 1:37 So now, I can do kenneth.pickpocket. 1:43 And just like any other function, I have to call it with parenthesis. 1:47 And since the method doesn't take any arguments other than self I don't put 1:50 anything inside of here. 1:55 And I get back False, so it randomly picked false. 1:57 So, cool. 2:01 Now, I don't usually like to show you clunky ways of achieving something but 2:02 I feel like this whole self thing needs a little bit more explanation. 2:06 Now, let's do the same method but 2:10 we're going to do it in a slightly different way, all right? 2:12 So, if I tried to Thief.pickpocket. 2:15 Then I get an error. 2:19 I get this TypeError saying that pickpocket is missing a required 2:20 positional argument, self. 2:23 Okay, so let's give it a self, pickpocket, and 2:26 I'm going to give it an instance of the class. 2:29 And this time I get False again. 2:33 So, we just ran the exact same code, but 2:35 this time we had to provide an argument to pickpocket or it failed, right? 2:37 Since we called it directly from the class, 2:41 we had to provide an instance that it would be used by. 2:42 So, let's add a little something to the class to make this instance use 2:46 more obvious. 2:49 I' m gonna go ahead and exit and them I'm gonna clear this screen. 2:50 I'm gonna hop back up here to this. 2:54 Okay, so inside pickpocket let's add a new line here, 2:55 print Called by, and then let's fill that in with self. 3:00 So, now our instance will print out who it is that's trying to pickpocket someone 3:05 else, okay? 3:10 Maybe not the best approach for a thief but 3:11 we're here to learn not to steal things from people. 3:13 So, from characters import Thief, Kenneth = Thief. 3:17 And now, let's do kenneth.pickpocket. 3:23 Okay, called by characters.Thief object at that address, and True. 3:27 Cool, that time I succeeded, all right? 3:31 So now, let's try our other method of it, Thief.pickpocket. 3:34 And we'll pass in the instance, which is kenneth. 3:38 And I get the same output, the exact same output, right? 3:42 Called by characters.thief object at 0x7f99b71edef0, all right? 3:45 Exactly same memory address. 3:50 So, the fact that we have the exact same memory address shows us that it's 3:54 using the exact same object for calling the method both times. 3:58 This self concept often trips up early programmers, but 4:03 practice makes perfect on it. 4:07 And thankfully, Python will gripe at you loudly if you forget to use self as 4:08 a parameter if you forget to call it on a method. 4:12 All right, one more thing about self. 4:17 We can always use self to talk about the current instance, like in the method. 4:19 So, let's check and 4:25 make sure that our thief is sneaky before we even attempt to pickpocket somebody. 4:27 So, let's take out this print line. 4:32 Cuz we don't need that. 4:35 And let's say if self.sneaky, and then we'll indent that. 4:36 Otherwise, we'll return False, okay? 4:41 So, if the instance's sneaky attribute is set to True, 4:44 then we'll try and pickpocket. 4:49 Otherwise, we just always return a False. 4:51 All right, so that's cool. 4:53 Now let's give that a try. 4:55 Come back down here. 4:57 From characters import thief. 5:01 kenneth = thief. 5:03 And let's try this. 5:07 So, kenneth.pickpocket. 5:08 And we get false, and if I run this another time or two I get, 5:10 yeah there we go, True, False, whatever. 5:13 Okay, so now let's make sure that I am not sneaky, all right? 5:16 I'm a clumsy non sneaky thief. 5:21 And now, let's try kenneth.pickpocket. 5:24 False, False, False, False, False, all right? 5:28 So, it's always False. 5:30 I'm gonna get caught cuz I'm not sneaky. 5:32 So, inside of a class's method, self always refers to the instance. 5:36 And I can use that to get to the instance's attributes and 5:40 even other methods. 5:43 Let's try this whole method thing out with a co-challenge or two. 5:45