Comments and C9 Transition

Quick reference

• 00:04 Okay, so we've built our first Python program, very simple program.
• 00:08 Like I said, this is the first program that all coders always do the Hello World
• 00:12 program, so you're in good company.
• 00:14 So in this video I want to expand upon this a little bit, talk about comments,
• 00:18 talk about a couple of other little things.
• 00:20 And it should be fun.
• 00:21 First things first, let's add a little bit more functionality to our program.
• 00:25 Up here at the top, let's type in import os, and
• 00:29 then os.system, and then parenthesis, and then clear.
• 00:36 Now, go ahead and
• 00:37 save this file, Ctrl+S on your keyboard, Cmd+S if you're on a Mac.
• 00:41 Come over here and click File > Save.
• 00:43 You see it right here says Ctrl+S as well.
• 00:45 And let's head back over to our terminal.
• 00:47 Now if you press the up arrow on your keyboard,
• 00:50 it will go to the last command you typed in.
• 00:52 So we don't have to keep typing in python, hello.py every time.
• 00:55 We can just type up on the keyboard and then hit Enter.
• 00:59 When you do see the whole thing cleared.
• 01:01 And right up here at the top says Hello world!
• 01:03 Now if we come down here and fill up the screen with a bunch more stuff, and
• 01:08 then run this file again.
• 01:10 Again, boom, it clears everything and then runs the program.
• 01:12 So that's what these two lines of code do.
• 01:16 We're important a module.
• 01:18 We don't really care what that means.
• 01:19 We'll talk about that much later.
• 01:21 And inside that module,
• 01:22 we can run this little command that just clears the screen.
• 01:26 So we're going to keep this at the top of all of our Python programs, so
• 01:29 that every time we run a program it just clears the screens.
• 01:32 It's a handy little thing to do.
• 01:33 For the rest of this video I want to talk a little bit more about what this
• 01:37 line of code is.
• 01:38 And I also want to talk about comments.
• 01:39 So first things first this is a print function and
• 01:42 we're going to get into functions much later.
• 01:46 But basically all this is doing is you could probably guess,
• 01:48 it's just printing something to the screen.
• 01:50 And what is it printing?
• 01:51 Whatever is inside these quotation marks, right?
• 01:54 Again, we're going to talk about functions later on and learn how to create our own
• 01:58 functions and learn all kinds of cool things about already made functions.
• 02:02 But for now, that's really all we need to know about this.
• 02:05 For the rest of this video, I want to talk about comments very quickly.
• 02:07 So a comment is created with a hashtag, a number sign.
• 02:12 And we can just type in whatever our comment is.
• 02:15 So we might type in print hello world to the screen.
• 02:20 And you'll notice everything is kind of grayed out.
• 02:24 Now if we save this and come back over to our terminal and run this again, and
• 02:28 notice that comment doesn't appear here.
• 02:31 And that's what comments do.
• 02:32 They're ignored by the program.
• 02:35 They're just for us as coders to sort of jog our memory of what the code is.
• 02:40 This seems kind of silly to write print Hello World to the screen,
• 02:44 the comment is longer than the actual code.
• 02:46 And normally, you wouldn't put a comment right here.
• 02:49 What you want to comment are big changes in your code,
• 02:52 big blocks of code that do new things.
• 02:54 And it's important because over time,
• 02:56 you're kind of forget what your code is supposed to do.
• 02:59 It just happens.
• 03:00 And you may have to come back six months from now and fix something,
• 03:04 update something, tweak something in your code, and you'll look at it and you go,
• 03:08 what in the world was I trying to do there.
• 03:10 And you won't remember because coding isn't always
• 03:12 obvious if you just glance at it.
• 03:14 Comments as so important and
• 03:16 you just want to be brief, just a few worlds that's really all.
• 03:19 It's also good if your working with teams and
• 03:21 you have other people looking at your code.
• 03:23 They need to know what your code is supposed to do so comments help with that.
• 03:27 There's lots of ways you can do comments.
• 03:28 You can do more than one line, as many as you like.
• 03:33 Some people like to do things like kind of wrap a comment in a comment, right?
• 03:41 That's kind of overboard, but this might be a good idea if you
• 03:46 have a major block of code and you really want to write three or
• 03:52 four different lines of code, you might do something like this.
• 03:55 It used to be popular to, at the beginning of your code, do something like this.
• 04:00 You could, let's go ahead and delete this.
• 04:05 And at the top and here you might explain what this program is supposed to do and
• 04:12 then you might go you Copyright (c) John Elder 2019.
• 04:17 That's kind of a popular thing that the people used to do.
• 04:19 You don't see that as much these days.
• 04:21 But you can do that.
• 04:22 So those are comments super important.
• 04:24 And try and just get in the habit of creating a comment for major changes in
• 04:29 your code, major new blocks of code and we'll get into this more as we go on.
• 04:33 And it will become apparent to you as a coder or when you should comment,
• 04:36 when you should not, it's just best practices.
• 04:38 So I should note, you can comment on lines of code too.
• 04:42 This is a comment.
• 04:44 And as soon as the Python interpreter sees the hashtag from there till the end of
• 04:48 a line it sees that as a comment.
• 04:50 So it'll still run this, it will just ignore this, right?
• 04:54 That's kind of cool, so those are comments.
• 04:57 But before we move forward very quickly for the rest of the course I'm going to be
• 05:01 using a different development environment than what we've set up here.
• 05:05 And I can pull this right up here.
• 05:06 This is what I'm going to be using.
• 05:07 This is called cloud nine, it's a cloud development tool.
• 05:11 It has everything in one screen.
• 05:13 So it has the files here on the left, it has the code here in the middle.
• 05:17 As the terminal down here at the bottom.
• 05:19 So whenever I type something in here, you follow along and
• 05:24 type it here in your Sublime Text, obviously right?
• 05:28 Anytime I make a command down here,
• 05:31 you'll do the exact same command in your terminal.
• 05:34 It's just I use this because it's all one screen and it's easier for teaching.
• 05:38 This actually doesn't exist anymore.
• 05:40 Amazon bought this company and they recently closed it down.
• 05:43 So I used to tell my students to use this tool as well, but
• 05:46 you can't use it anymore.
• 05:48 So you'll just have to use the sublime text editor that we downloaded and
• 05:51 installed in the Git Bash terminal.
• 05:53 So this is what I'm going to be using throughout the rest of the course.
• 05:56 So you should be able to follow along with no problem.
• 05:58 Like I said, the commands I typed down here will be the exact commands
• 06:02 that you type in your terminal.
• 06:03 The code that I write up here will be the exact code that you write in Sublime Text.
• 06:08 You notice here on the left, you have this directory of files.
• 06:12 It's the same directory that I'll have right here.
• 06:15 So anytime I add a new file over here, you'll do the same thing over here,
• 06:21 create a new file there then it will pop up.
• 06:25 You save it just like we saved the first one.
• 06:28 Save as file2.py whatever.
• 06:31 You see what pops right up.
• 06:33 You can toggle between them and should be pretty simple.
• 06:35 So that's all for this video.
• 06:36 In the next video we're going to jump in and talk about variables.

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