1 00:00:00,270 --> 00:00:04,920 Throughout all of yesterday, we've been using other people's classes. 2 00:00:05,460 --> 00:00:10,460 And we said that a class is simply just a blueprint for creating an eventual 3 00:00:11,490 --> 00:00:13,800 object. In this lesson, 4 00:00:13,830 --> 00:00:17,490 we're going to talk about how we can create our own classes, 5 00:00:17,970 --> 00:00:22,830 so our own blueprints, which we can use to create our own objects. 6 00:00:23,910 --> 00:00:28,080 Now let's go ahead and create our own custom classes in code. 7 00:00:28,530 --> 00:00:33,240 Go ahead and create a new project either in PyCharm or Repl.it wherever you 8 00:00:33,240 --> 00:00:37,140 prefer. And we're going to name it day-17-start, 9 00:00:37,950 --> 00:00:41,430 and then hit create. And again, as always, 10 00:00:41,460 --> 00:00:46,170 once you've created your project, it's time to create your first file 11 00:00:46,170 --> 00:00:48,090 which we're going to name main.py. 12 00:00:48,480 --> 00:00:52,890 And then we can collapse our project sidebar and focus on the code. 13 00:00:54,240 --> 00:00:59,070 So how do we create a class? The syntax looks very simple. 14 00:00:59,100 --> 00:01:05,120 You have the "class" keyword followed by the name of your class and then a colon 15 00:01:05,122 --> 00:01:05,123 . 16 00:01:05,129 --> 00:01:09,360 and then all of the code that's in your class will follow this and it will be 17 00:01:09,360 --> 00:01:13,320 indented. Let's create our very first class in Python. 18 00:01:13,920 --> 00:01:14,760 As I mentioned, 19 00:01:14,790 --> 00:01:19,440 the way that we would create a class is first by using the class keyword. 20 00:01:20,250 --> 00:01:22,740 And then we get to give our class a name. 21 00:01:23,220 --> 00:01:28,220 Let's say that we're building a website and we need a class to model our website's 22 00:01:29,490 --> 00:01:30,323 users. 23 00:01:30,570 --> 00:01:35,570 So this class is basically going to be the blueprint to represent what our 24 00:01:35,880 --> 00:01:39,450 users have and what they can do on our website. 25 00:01:40,170 --> 00:01:42,000 Let's call our class User 26 00:01:42,510 --> 00:01:47,510 and then we finished this declaration with a colon as usual. And everything 27 00:01:48,480 --> 00:01:50,010 else that's going to go inside 28 00:01:50,010 --> 00:01:54,180 this class is going to need to be indented after the colon. 29 00:01:54,870 --> 00:01:57,780 Let's start out with a completely empty class. 30 00:01:58,200 --> 00:02:02,820 Our user class is going to do absolutely nothing for now. However, 31 00:02:02,820 --> 00:02:04,530 because I've created my blueprint 32 00:02:04,620 --> 00:02:08,310 I can already use it to create my first user object. 33 00:02:08,940 --> 00:02:11,220 So let's say I wanted to create a user_1 34 00:02:11,640 --> 00:02:14,490 and I'm going to create it using that class, 35 00:02:14,880 --> 00:02:17,760 which notice it's now being recognized by PyCharm, 36 00:02:18,150 --> 00:02:21,330 and it's got the C symbol next to it. And of course, 37 00:02:21,330 --> 00:02:23,850 to initialize an object from a class, 38 00:02:23,880 --> 00:02:26,190 we have to add the parentheses at the end. 39 00:02:26,940 --> 00:02:31,020 Now we get an error here because there's an indent expected. 40 00:02:31,440 --> 00:02:33,540 So basically Python doesn't like it 41 00:02:33,630 --> 00:02:38,340 when you create something like a class or when you create something like a 42 00:02:38,340 --> 00:02:40,950 function and you have a colon, 43 00:02:41,280 --> 00:02:46,080 but you don't have anything inside that function or class. For example, 44 00:02:46,080 --> 00:02:49,560 if I just immediately wanted to print "hello" afterwards, 45 00:02:49,590 --> 00:02:52,650 I get exactly the same error; indent expected. 46 00:02:53,100 --> 00:02:56,640 It's expecting this function that you've created or this class 47 00:02:56,640 --> 00:03:01,640 you've just created to have some sort of content before you go ahead and do something 48 00:03:01,810 --> 00:03:04,630 else. So how can we fix this? Well, 49 00:03:04,660 --> 00:03:08,200 if we actually really want to leave this function or this class empty, 50 00:03:08,320 --> 00:03:10,390 we can use a keyword which is pass. 51 00:03:10,960 --> 00:03:15,370 And all it does is it just passes. It says, I don't want to have a go right now. 52 00:03:15,640 --> 00:03:19,840 Just continue to the next line of code. And this gets rid of our errors 53 00:03:19,900 --> 00:03:21,880 both in the function declaration 54 00:03:22,210 --> 00:03:26,650 as well as in our class declaration. We've now essentially completed the 55 00:03:26,650 --> 00:03:29,050 first step towards creating our custom classes, 56 00:03:29,320 --> 00:03:34,320 which is writing the declaration and then building an object called user_1 out 57 00:03:34,960 --> 00:03:39,370 of that class. And we've also seen how to name classes in Python. 58 00:03:39,940 --> 00:03:43,960 Now the name of the class should have the first letter of every word 59 00:03:44,140 --> 00:03:44,980 capitalized. 60 00:03:45,550 --> 00:03:50,550 And this particular style of naming in Programming is known as Pascal case. 61 00:03:52,060 --> 00:03:55,030 So if you think of Blaise Pascal as a person, 62 00:03:55,060 --> 00:03:56,950 then we know that everybody's name, 63 00:03:56,950 --> 00:04:01,950 every person's name, has the first letter capitalized and also the first letter 64 00:04:02,400 --> 00:04:04,890 of their surname or their middle name 65 00:04:04,980 --> 00:04:08,100 and basically every subsequent name capitalized. Now, 66 00:04:08,130 --> 00:04:12,180 this is different from another type of casing which you may have come across 67 00:04:12,420 --> 00:04:13,800 which is called camel casing. 68 00:04:14,160 --> 00:04:19,160 And camel casing is only different from Pascal case because the first word is 69 00:04:19,380 --> 00:04:23,910 lowercase, but every subsequent word it has it's first letter capitalized in 70 00:04:24,030 --> 00:04:27,870 exactly the same way as Pascal case. And finally, 71 00:04:27,900 --> 00:04:31,590 we've also come across snake case where all the words are lowercase 72 00:04:31,740 --> 00:04:32,880 but they're separated by 73 00:04:32,880 --> 00:04:37,830 an underscore. In Python programming, you won't see a lot of camel casing. 74 00:04:37,860 --> 00:04:41,430 You will see Pascal case being used for the class names, 75 00:04:41,760 --> 00:04:45,210 snake case being used pretty much to name everything else.