1 00:00:04,700 --> 00:00:08,090 In this video, we're going to take a break from writing code and look at 2 00:00:08,090 --> 00:00:12,440 style of our code. The first place to start when talking about style and 3 00:00:12,440 --> 00:00:22,490 Python code is PEP 8. So I'm going to search for PEP 8, and the first result 4 00:00:22,490 --> 00:00:25,880 should be the page of python.org and you can see that is the case for me, 5 00:00:25,880 --> 00:00:31,339 PEP 8 style guide. So I'm going to open that up, and you can see that, in fact, 6 00:00:31,340 --> 00:00:39,580 they have got a PEP 8 style guide for Python code. So a PEP is a Python Enhancement Proposal. 7 00:00:39,580 --> 00:00:42,820 All changes in new features to the python language start with a 8 00:00:42,829 --> 00:00:47,840 proposal. The proposal is reviewed, discussed, improved if necessary, and then 9 00:00:47,840 --> 00:00:54,109 either accepted or rejected. Until 2018, Guido van Rossum made the final decision 10 00:00:54,109 --> 00:00:58,280 about whether to implement a PEP or not. Since then, the decision is taken by a 11 00:00:58,280 --> 00:01:03,710 group of people. Now you can see who they are by looking at PEP 0013, so let's just open 12 00:01:03,710 --> 00:01:10,520 another tab here. I'm going to paste the link in the resources section, as 13 00:01:10,520 --> 00:01:17,509 per normal. So as you can see, any changes to python are made via a PEP, 14 00:01:17,509 --> 00:01:22,460 and that includes administrative changes, as well as technical ones. Scrolling down, 15 00:01:22,460 --> 00:01:25,980 we've got this steering committee, current steering council, I should say. 16 00:01:25,980 --> 00:01:29,659 You may recognize three of the names from the PEP 8 page we were just looking at. 17 00:01:29,659 --> 00:01:33,110 I'll leave you to read this PEP 0013 if you're interested, and 18 00:01:33,110 --> 00:01:38,540 I'll switch back to the PEP 8 page now. Alright, so PEP 8 was written by Guido 19 00:01:38,540 --> 00:01:43,120 van Rossum, Barry Warsaw and Nick Coghlan, way back in 2001. 20 00:01:43,120 --> 00:01:46,939 They've all been involved with Python for a long time. Guido wrote the first 21 00:01:46,939 --> 00:01:51,799 version and a few subsequent ones, starting back in 1989. Now I don't 22 00:01:51,799 --> 00:01:55,670 suggest you read all of this document right away. Most of the code examples 23 00:01:55,670 --> 00:01:59,780 won't make much sense, and you'll find it confusing. I'm going to go through some 24 00:01:59,780 --> 00:02:03,049 sections that will make sense. After that, check back in here as you 25 00:02:03,049 --> 00:02:07,460 learn more about Python. So the last two paragraphs of the introduction are worth 26 00:02:07,460 --> 00:02:12,830 reading. This style guide evolves over time. Python 3 has some features that weren't 27 00:02:12,830 --> 00:02:18,350 available in Python 2, and the guide has had to change to deal with new features. 28 00:02:18,350 --> 00:02:22,100 The last paragraph is important. If you work on a project that has its own style 29 00:02:22,100 --> 00:02:26,720 guide, then that should take precedence over this one. For example, google have 30 00:02:26,720 --> 00:02:31,040 their own Python style guide. If you end up working for Google, then your code 31 00:02:31,040 --> 00:02:35,750 should conform to their guide. Alright, so moving down, read through the 32 00:02:35,750 --> 00:02:41,390 next section - A Foolish Consistency is the Hobgoblin of Little Minds. So it contains 33 00:02:41,390 --> 00:02:45,710 some useful advice on when you should not follow a style guide. Point number 34 00:02:45,710 --> 00:02:50,960 three is important; Don't change code to make it conform to a certain style, when 35 00:02:50,960 --> 00:02:55,160 there's no other reason to be changing that code. A simple typing error could 36 00:02:55,160 --> 00:02:58,760 break the code and cause all sorts of problems. Unless you're prepared to 37 00:02:58,760 --> 00:03:02,930 explain why you broke a major program, such as Google search engine, just 38 00:03:02,930 --> 00:03:06,590 because you didn't like the name of a variable, then don't do it. If you're 39 00:03:06,590 --> 00:03:10,310 going to be changing the program anyway, and it's going to be tested afterwards, 40 00:03:10,310 --> 00:03:14,900 then you could take the opportunity to clean it up. I'm going to skip, as we go 41 00:03:14,900 --> 00:03:19,460 down, most of this Code Lay-out section. That's not because it isn't important - 42 00:03:19,460 --> 00:03:24,040 it is - but it contains a lot of Python statements that we haven't seen yet. 43 00:03:24,040 --> 00:03:31,240 So moving down to the tabs and spaces section, the recommendation there is to 44 00:03:31,250 --> 00:03:35,720 use spaces to indent your code. That's important for programmers from other 45 00:03:35,720 --> 00:03:40,820 languages. If you're used to using tabs, then you should use spaces in Python. 46 00:03:40,820 --> 00:03:45,350 If you don't, and your IDE said to use tabs, then you'll get problems on Python 47 00:03:45,350 --> 00:03:50,390 3 when you open your code, written to use spaces. So next is the Maximum Line 48 00:03:50,390 --> 00:03:55,490 Length. Now pay attention to this section. These suggested line lengths are intended 49 00:03:55,490 --> 00:03:59,060 for when you edit Python code in a terminal, which is typically 80 50 00:03:59,060 --> 00:04:05,000 characters wide. As you'll see soon, the JetBrains IDEs suggest 120 characters, 51 00:04:05,000 --> 00:04:10,460 rather than 79. Google suggest a maximum line length of 80 characters, with a few 52 00:04:10,460 --> 00:04:15,500 exceptions. Stick to 72 characters for comments and docstrings, because it's 53 00:04:15,500 --> 00:04:20,269 very hard for tools to format them. For this course, I'll generally stick to less 54 00:04:20,269 --> 00:04:23,900 than 80 characters for the line length. That makes it easier for you to see the 55 00:04:23,900 --> 00:04:28,580 code in the videos, and allows the code to display correctly in an e-book. 56 00:04:28,580 --> 00:04:37,500 Alright, so moving on. I'm going to skip to the Naming Conventions section. 57 00:04:37,980 --> 00:04:42,260 So the Naming Conventions section starts with an admission, that a lot of the code 58 00:04:42,269 --> 00:04:47,489 in the Python libraries are quote, a bit of a mess, unquote, as far as sticking to 59 00:04:47,489 --> 00:04:52,559 the naming conventions. This style guide was written in 2001, and Python had been 60 00:04:52,559 --> 00:04:57,179 used for 10 years before this guide was written. When you come to use code from 61 00:04:57,180 --> 00:05:00,899 the standard library, which we'll be doing in later videos in the course, you'll 62 00:05:00,900 --> 00:05:05,020 find that many things don't conform to this guide. Don't worry about it. 63 00:05:05,020 --> 00:05:08,600 The developers have read point three above, which I talked about earlier in the 64 00:05:08,609 --> 00:05:13,109 video, and not changed the style just for the sake of it. We've used variables in 65 00:05:13,109 --> 00:05:17,640 our code so far, so let's see what the guide has to say about variable names, 66 00:05:17,640 --> 00:05:20,939 and that's specifically, as we go down a little bit further now, in the Function and 67 00:05:20,939 --> 00:05:29,459 Variable Names section. Variable names should follow the same convention as 68 00:05:29,459 --> 00:05:34,349 function names, which means they should be in lowercase, with underscores used to 69 00:05:34,349 --> 00:05:39,539 separate words if necessary. Mixed case, which is the convention in languages 70 00:05:39,539 --> 00:05:44,699 like Java and C++, should be avoided. Okay, so bookmark this document in your 71 00:05:44,700 --> 00:05:49,840 browser and refer back to it as we cover more Python statements in the course. 72 00:05:49,840 --> 00:05:53,669 Alright, so back in IntelliJ, you can't actually see it at the moment because 73 00:05:53,669 --> 00:05:58,940 of how compressed I've got my screen, so that you can see the videos in a good font, 74 00:05:58,940 --> 00:06:03,719 but there's a vertical guide in IntelliJ set at 120 characters. Now what 75 00:06:03,719 --> 00:06:09,149 I can actually do, is I'm going to temporarily just put some long code in 76 00:06:09,149 --> 00:06:13,019 here, just so we can see it. I'm gonna put a hash there for a comment and I'm just 77 00:06:13,019 --> 00:06:18,779 going to paste some code, so keep pasting, and there's the vertical guide that I 78 00:06:18,779 --> 00:06:22,019 was talking about. Now obviously, you can see we've got some warnings, now that 79 00:06:22,019 --> 00:06:25,109 I've done that. We've exceeded the 120 characters. So this is basically the 80 00:06:25,109 --> 00:06:30,179 vertical guide I'm talking about, currently set to 120 characters. Alright, so I'm just 81 00:06:30,179 --> 00:06:36,299 going to undo that change, or rather delete that line. Now if you want to 82 00:06:36,299 --> 00:06:41,369 conform to the Python style guide, 120 characters is too long. The JetBrains 83 00:06:41,369 --> 00:06:44,789 IDEs allow you to change the position of that guide. You can even set 84 00:06:44,789 --> 00:06:48,059 more than one, which is useful. So to do that, let's have a look at how to do that. 85 00:06:48,059 --> 00:06:51,110 We're gonna to go into File Settings. 86 00:06:51,330 --> 00:06:54,900 Then you need to click on Editor and then Code Style and I'm already there, you can see. 87 00:06:54,900 --> 00:06:58,440 Now, you can see under visual guides, I've got nothing in there at the moment, 88 00:06:58,440 --> 00:07:03,000 although it does say hard rap at 120, above that. Now most modern IDEs will 89 00:07:03,000 --> 00:07:07,760 have a similar setting. I want comments and docstrings to be no longer than 72 90 00:07:07,760 --> 00:07:12,680 characters, and code to stop at 80 characters. So to achieve that, and the 91 00:07:12,690 --> 00:07:19,050 visual guides down here, I'm going to enter 72 comma 80 in this box, and click 92 00:07:19,050 --> 00:07:24,360 on OK. And now you can see, we've got these fake vertical guides to show us 93 00:07:24,360 --> 00:07:28,379 where 72 and 80 characters are, and now I can see it clearly on my screen, 94 00:07:28,379 --> 00:07:32,879 so that's good. Now there's still the darker guide at 120 characters, which we can't 95 00:07:32,879 --> 00:07:36,780 see, unless I go back and do what I did earlier, and that's set by that hard 96 00:07:36,780 --> 00:07:40,050 wrap at setting, which you saw at the top, and you can go back into the settings to 97 00:07:40,050 --> 00:07:43,319 change that if you want. But I'll leave that, as is. Alright, so what I want to do, 98 00:07:43,319 --> 00:07:47,039 though, is finish this video with a challenge. You need to open up the escape 99 00:07:47,039 --> 00:07:51,120 char.py from the previous section, and I've actually copied it into this 100 00:07:51,120 --> 00:07:57,040 project, so open that up. 101 00:07:57,040 --> 00:08:00,860 Now this doesn't conform to the PEP 8 style guide. 102 00:08:00,860 --> 00:08:04,080 I don't want you to change the code at the moment. That's because I'm going to show 103 00:08:04,080 --> 00:08:08,490 you a safer way of changing it in the next video. Your challenge is simply to 104 00:08:08,490 --> 00:08:13,650 identify the things that don't conform to the PEP 8 style guide. There are three 105 00:08:13,650 --> 00:08:18,389 problems with this code, which will need changing on 6 lines, but again, don't 106 00:08:18,389 --> 00:08:22,500 change them yet. Just work out what these things are - the things that don't conform 107 00:08:22,500 --> 00:08:27,090 to the PEP 8 style guide. I'll go over them, and show you a cool way to fix them, 108 00:08:27,090 --> 00:08:30,289 in the next video.