1 00:00:00,760 --> 00:00:02,260 In previous lessons, 2 00:00:02,290 --> 00:00:07,150 I've already mentioned how important it is in Python to be aware of your 3 00:00:07,150 --> 00:00:12,010 indentation. So we know that when we create a function like this, 4 00:00:12,040 --> 00:00:15,850 that every line that comes after this definition 5 00:00:16,120 --> 00:00:20,590 that is indented is going to be inside this function. 6 00:00:21,130 --> 00:00:23,050 So by indented, I mean 7 00:00:23,050 --> 00:00:26,650 it's shifted to the right by four spaces like this. 8 00:00:27,280 --> 00:00:31,990 So if you imagine each dot as a space, then this is a single block of code. 9 00:00:33,580 --> 00:00:37,900 And if we want to continue adding to this block of code inside my function, 10 00:00:38,170 --> 00:00:41,650 then we would continue adding lines of code, which are indented. 11 00:00:42,430 --> 00:00:47,430 So you have to almost visualize for yourself this invisible line around these 12 00:00:47,560 --> 00:00:51,100 blocks of code, which are indented. Now, 13 00:00:51,190 --> 00:00:54,190 if my code was written like this on the other hand, 14 00:00:54,550 --> 00:00:59,550 then the block of code is in fact only this part. And this print statement will 15 00:01:02,110 --> 00:01:07,000 not get triggered when this function gets triggered because it's independent 16 00:01:07,270 --> 00:01:12,130 from this function because it's not indented. Now, a simple way 17 00:01:12,130 --> 00:01:16,840 that I like to think about this kind of indentation is kind of like the file 18 00:01:16,840 --> 00:01:19,840 structure you see when you go into finder on the Mac, 19 00:01:19,870 --> 00:01:22,390 or when you go into Explorer on Windows. 20 00:01:23,380 --> 00:01:24,910 If we have a function, 21 00:01:25,000 --> 00:01:29,950 it's kind of like a folder and anything that goes inside the function, 22 00:01:29,980 --> 00:01:33,100 for example, if I throw this file inside the function, 23 00:01:33,460 --> 00:01:36,160 then you notice that it gets indented, right? 24 00:01:36,670 --> 00:01:39,250 And this way it shows to you very, 25 00:01:39,250 --> 00:01:42,130 very clearly that these two files print- 26 00:01:42,130 --> 00:01:46,420 hello and print-world are living inside this folder, 27 00:01:46,480 --> 00:01:50,920 my function. And this is the equivalent of this code. 28 00:01:51,400 --> 00:01:56,400 We have this folder say, my_function, and it contains these two lines of code. 29 00:01:58,090 --> 00:01:59,260 Now, on the other hand, 30 00:01:59,290 --> 00:02:04,290 if I take this print world and I put it outside of the function folder, 31 00:02:05,470 --> 00:02:09,490 then you can see that this is completely independent from that folder. 32 00:02:10,030 --> 00:02:14,170 And it's now indented at the same level as the function. 33 00:02:14,800 --> 00:02:19,780 So this is the equivalent of this code, where we've got this print- 34 00:02:19,780 --> 00:02:21,820 hello being inside the 35 00:02:21,820 --> 00:02:26,820 my_function and this print-world being outside and at the same indentation level 36 00:02:28,240 --> 00:02:31,840 as this function definition. Now, 37 00:02:31,840 --> 00:02:35,920 the indentation gets a little bit more complicated when we have other blocks of 38 00:02:35,920 --> 00:02:40,240 code. So for example, the, if/elif/else statements. 39 00:02:40,420 --> 00:02:41,800 They have blocks of code, 40 00:02:42,190 --> 00:02:45,430 which need to be indented to be inside the block. 41 00:02:45,940 --> 00:02:49,240 For loops need to be indented to be inside the loop. 42 00:02:49,870 --> 00:02:54,820 And it's very important that you get used to looking at blocks of code like 43 00:02:54,820 --> 00:02:58,720 this. So for example, if we were to expand our simple 44 00:02:59,410 --> 00:03:03,640 my_function and add a whole bunch of code into it, 45 00:03:04,150 --> 00:03:08,890 then we would have to indent all of those lines of code by four spaces 46 00:03:09,070 --> 00:03:13,810 represented by the four dots here. Now, if we wanted to have 47 00:03:13,810 --> 00:03:17,740 another block of code inside this if statement, 48 00:03:18,040 --> 00:03:20,950 then this line has to be indented, 49 00:03:21,190 --> 00:03:23,470 a further four spaces. 50 00:03:24,310 --> 00:03:27,070 So this is the function block, 51 00:03:28,000 --> 00:03:30,910 this is the if block, 52 00:03:31,600 --> 00:03:36,600 this is the elif block and you have to be able to see all of this while just 53 00:03:38,230 --> 00:03:43,120 looking at the indentation. If we wanted to represent this, 54 00:03:43,180 --> 00:03:47,500 then it's almost like creating a new folder. Let's call it the 55 00:03:47,530 --> 00:03:50,770 If sky == clear. 56 00:03:52,480 --> 00:03:56,740 And this if block goes inside my function, so it's indented. 57 00:03:57,490 --> 00:04:01,810 Now, if I wanted to have a print statement, 58 00:04:01,840 --> 00:04:06,190 let's call it print-blue inside this if statement. 59 00:04:06,220 --> 00:04:10,390 So this is what should be executed if this function gets called 60 00:04:10,510 --> 00:04:13,630 and if the sky is equal to clear, well 61 00:04:13,630 --> 00:04:16,390 then this line is indented twice. 62 00:04:17,140 --> 00:04:22,140 And that is the equivalent of four spaces in our code, like this. 63 00:04:24,100 --> 00:04:26,470 Now, every time I've talked about indentation, 64 00:04:26,500 --> 00:04:31,500 I've been talking about spaces and actually there's two ways of creating 65 00:04:31,750 --> 00:04:35,080 indentation. You don't have to just use spaces. 66 00:04:35,260 --> 00:04:40,260 You can also use tabs and that's created using the tab key on your keyboard, 67 00:04:40,720 --> 00:04:42,730 which can look a little bit like this. 68 00:04:43,840 --> 00:04:48,550 Now there's a lot of debate around spaces and tabs where some people prefer 69 00:04:48,550 --> 00:04:52,570 using spaces to indent, other people prefer tabs to indent. 70 00:04:53,050 --> 00:04:56,740 And there's a lot of people arguing in the coding community. 71 00:04:57,250 --> 00:05:01,720 And I think this excerpt from one of my favourite shows really demonstrates this. 72 00:05:11,980 --> 00:05:15,940 Richard what's wrong? Nothing, nothing, literally. It's all good. 73 00:05:20,640 --> 00:05:24,750 Come on. Oh my God. Your roommates are right. You really hate spaces. 74 00:05:25,050 --> 00:05:28,920 No, no, no, no. I don't. It's not hate, hate is a strong word. Um, 75 00:05:29,460 --> 00:05:32,490 truth be told I do have a slight preference for tabs, 76 00:05:32,520 --> 00:05:34,360 but that's only because I'm anal 77 00:05:34,360 --> 00:05:37,590 and because I prefer precision. 78 00:05:40,390 --> 00:05:42,160 Well, not to pick a fight here, 79 00:05:42,160 --> 00:05:45,580 but if you really care about precision why don't you use spaces? 80 00:05:46,360 --> 00:05:50,050 But whatever, once it goes through the compiler, it's the same thing, right? 81 00:05:51,230 --> 00:05:53,300 Yeah. Yeah. Technically, yes. 82 00:05:53,630 --> 00:05:54,463 Right. 83 00:05:59,150 --> 00:06:03,380 I guess I just, I just don't understand why anyone would use spaces over tabs. 84 00:06:03,380 --> 00:06:04,850 Like if it's all the same, 85 00:06:04,920 --> 00:06:08,300 why not just use tabs? Because it could look different on other people's 86 00:06:08,300 --> 00:06:11,480 computers. Tabs create smaller file sizes. All right. 87 00:06:11,480 --> 00:06:13,160 I run a compression company. Trust me. 88 00:06:13,160 --> 00:06:17,090 I've devoted my life to minimalizing file sizes. It's what I do. I mean, 89 00:06:17,090 --> 00:06:21,440 I do not get why anyone would use spaces over tabs. I mean, 90 00:06:21,440 --> 00:06:26,390 why not just use VIM over Emacs? I do use VIM over Emacs. Oh, God help us. 91 00:06:26,930 --> 00:06:31,220 Okay. Uh, you know what? I just, I don't think this is gonna work. 92 00:06:31,310 --> 00:06:33,080 I'm so sorry. Uh, I mean like what, 93 00:06:33,260 --> 00:06:35,720 we're going to bring kids into this world with that over the head. 94 00:06:35,720 --> 00:06:37,820 Stuff's not really fair to them. Don't you think? Kids? 95 00:06:37,820 --> 00:06:39,800 we haven't even slept together. And guess what? 96 00:06:40,010 --> 00:06:42,920 It's never going to happen now because there is no way I'm going to be with 97 00:06:42,920 --> 00:06:45,440 someone who uses spaces over tabs. 98 00:06:46,260 --> 00:06:50,520 So should you be using spaces or should you be using tabs? 99 00:06:50,580 --> 00:06:55,580 The age old question and the extent to which people obsess over this question, 100 00:06:56,430 --> 00:07:01,050 it really shows in this 2017 Stack Overflow developer survey, 101 00:07:01,140 --> 00:07:05,070 where they are asked the developers, do you use spaces or do you use tabs? 102 00:07:05,490 --> 00:07:08,010 And then they compare it against their annual salary 103 00:07:08,070 --> 00:07:13,070 and somehow have managed to show that the people who use spaces seem to earn a 104 00:07:13,320 --> 00:07:15,480 lot more than the people who use tabs. 105 00:07:16,830 --> 00:07:21,830 Now the official guide from the Python community is in fact to use spaces. 106 00:07:23,010 --> 00:07:25,890 So if you click on the section, tabs or spaces, 107 00:07:26,220 --> 00:07:28,350 they tell you in no uncertain words, 108 00:07:28,350 --> 00:07:31,650 that spaces are the preferred indentation method. 109 00:07:32,220 --> 00:07:34,620 And in fact, in Python 3, 110 00:07:34,980 --> 00:07:39,980 you can't mix a code file that uses tabs and spaces for indentation in the same 111 00:07:41,190 --> 00:07:45,720 file. And it also tells you that in order to indent a line of code, 112 00:07:45,750 --> 00:07:49,110 it should be indented using four spaces, 113 00:07:49,350 --> 00:07:53,520 so four hits of the space bar. Now, 114 00:07:53,520 --> 00:07:57,270 for a lot of people, that may seem quite inefficient because I have to hit my 115 00:07:57,270 --> 00:07:58,103 space bar 116 00:08:00,060 --> 00:08:03,480 four times in order to achieve a single indent. 117 00:08:03,600 --> 00:08:08,070 And you've seen how much we indent throughout our code. So it seems very, 118 00:08:08,130 --> 00:08:09,420 very inefficient. 119 00:08:10,110 --> 00:08:13,410 But luckily in most code editors, 120 00:08:13,680 --> 00:08:18,680 they actually have a setting that allows you to indent using spaces, 121 00:08:19,830 --> 00:08:22,860 changing the indent size to four. 122 00:08:23,430 --> 00:08:25,140 And when you hit the tab key, 123 00:08:25,500 --> 00:08:28,920 it will automatically insert four spaces, 124 00:08:29,220 --> 00:08:33,030 which you can tell when you're trying to highlight this space, 125 00:08:33,030 --> 00:08:36,120 you can see the cursor is jumping four times. 126 00:08:36,990 --> 00:08:41,990 This means that you get to hit tab once and that your code is in line with the 127 00:08:42,840 --> 00:08:45,510 guidance because the hind the scenes 128 00:08:45,510 --> 00:08:48,900 your code editor is inserting four spaces. 129 00:08:50,430 --> 00:08:54,420 So I hope that clears up a little bit on tabs versus spaces. 130 00:08:54,750 --> 00:08:59,400 And I highly recommend you to head over to the course resources and click on the link 131 00:08:59,430 --> 00:09:03,660 to go to the style guide for Python code and take a look through the parts about 132 00:09:03,660 --> 00:09:08,190 indentation. Now in the next lesson, I've got a quick quiz for you 133 00:09:08,370 --> 00:09:12,720 to test your knowledge on indentation. So for all of that and more, 134 00:09:13,110 --> 00:09:14,340 I'll see you on the next lesson.