1 00:00:00,000 --> 00:00:04,990 As we start the Python Quick Start, we're going to use the traditional 2 00:00:05,000 --> 00:00:06,990 "Hello, World!" program. 3 00:00:07,000 --> 00:00:12,990 And purpose of "Hello, World!" is not an exercise to find the simplest form of 4 00:00:13,000 --> 00:00:15,990 code in a particular language, or anything like that. 5 00:00:16,000 --> 00:00:18,990 It's actually to learn about the development environment, to learn about what we 6 00:00:19,000 --> 00:00:20,990 call the development cycle: 7 00:00:21,000 --> 00:00:27,990 what it takes to edit, and to test, and to change, and to test and to run code 8 00:00:28,000 --> 00:00:29,990 in a particular environment. 9 00:00:30,000 --> 00:00:34,990 And so for this purpose we use the simplest form of a program itself, so that 10 00:00:35,000 --> 00:00:37,990 that can get out of the way and then we can focus on the environment. 11 00:00:38,000 --> 00:00:41,990 In this case, I've this up here on the screen in Eclipse. 12 00:00:42,000 --> 00:00:44,990 And this is Eclipse using Pydev, which is a Python development environment that 13 00:00:45,000 --> 00:00:46,990 runs inside of Eclipse. 14 00:00:47,000 --> 00:00:50,990 Eclipse is an integrated development environment originally written for 15 00:00:51,000 --> 00:00:53,990 developing in Java, but it has plug- ins for a lot of different languages. 16 00:00:54,000 --> 00:00:59,990 And Pydev is actually a pretty good plug-in for the Python language. 17 00:01:00,000 --> 00:01:01,990 And so, we'll be using this throughout this course. 18 00:01:02,000 --> 00:01:06,990 You do not have to use Eclipse, and if you have some other development 19 00:01:07,000 --> 00:01:11,990 environment that you prefer, or you just want to use an editor and a command line, 20 00:01:12,000 --> 00:01:12,990 that's perfectly fine. 21 00:01:13,000 --> 00:01:16,990 You can do all of the exercises; you do not need to use Eclipse. 22 00:01:17,000 --> 00:01:21,990 The reason that I'm using Eclipse is because it's convenient for the purpose of teaching. 23 00:01:22,000 --> 00:01:23,990 I've got everything that I need right up here on the screen. 24 00:01:24,000 --> 00:01:28,990 I can run code, I get the results of code, and it works well for the purpose of 25 00:01:29,000 --> 00:01:32,990 teaching, but you don't need to use it for your development work. 26 00:01:33,000 --> 00:01:36,990 And you do not need to use it to follow along in the exercises. 27 00:01:37,000 --> 00:01:39,990 In Eclipse, if I want to run this Hello, World!, 28 00:01:40,000 --> 00:01:44,990 I simply click on this Run button up here, and it'll ask me, How I want to run it? 29 00:01:45,000 --> 00:01:46,990 and I'm going to select Python Run. 30 00:01:47,000 --> 00:01:48,990 I only need to do this the first time I run a script. 31 00:01:49,000 --> 00:01:51,990 So I'm going to say OK. 32 00:01:52,000 --> 00:01:55,990 And here we have the result down here: "Hello, World!" 33 00:01:56,000 --> 00:01:59,990 If I were running this in another environment and I actually have this script 34 00:02:00,000 --> 00:02:01,990 loaded up here on a Unix Server - 35 00:02:02,000 --> 00:02:03,990 this is my Unix Server - 36 00:02:04,000 --> 00:02:08,990 there is the script, you see it's exactly the same. 37 00:02:09,000 --> 00:02:14,990 And if run it I say ./hello.py, and it runs it. 38 00:02:15,000 --> 00:02:18,990 An important part of this is this shebang line. 39 00:02:19,000 --> 00:02:22,990 If we look here in Eclipse, we see this shebang line here. 40 00:02:23,000 --> 00:02:27,990 In many environments, mostly Unix- based environments, but this includes 41 00:02:28,000 --> 00:02:31,990 Macintosh and it includes many, many web servers that are running Unix-based 42 00:02:32,000 --> 00:02:34,990 operating systems, like Linux or PSD, 43 00:02:35,000 --> 00:02:37,990 this shebang line is actually very important. 44 00:02:38,000 --> 00:02:41,990 It's called a shebang line because it's starts with a hash and then has an 45 00:02:42,000 --> 00:02:44,990 exclamation mark, which is sometimes called a bang. 46 00:02:45,000 --> 00:02:52,990 And then after that it has the path to the interpreter that will be used to run the script. 47 00:02:53,000 --> 00:02:57,990 When the script is executed and the shell sees it, it will look here for the 48 00:02:58,000 --> 00:03:00,990 interpreter and then use that to run the script. 49 00:03:01,000 --> 00:03:04,990 So sometimes you'll see a bash up here, or Perl, or something like that. 50 00:03:05,000 --> 00:03:09,990 And all that's doing is it's telling the shell to use that interpreter to run 51 00:03:10,000 --> 00:03:10,990 whatever script is there. 52 00:03:11,000 --> 00:03:13,990 For Python, it's going to be something like this. 53 00:03:14,000 --> 00:03:15,990 It might be #!/usr/bin/python3. 54 00:03:16,000 --> 00:03:20,990 It might be #!/usr/local/bin/python3. 55 00:03:21,000 --> 00:03:30,990 It might be #!/usr/bin/env python3, something like that. 56 00:03:31,000 --> 00:03:34,990 In this case, I'm using #!/usr/bin/python3 because I know that, that works in the 57 00:03:35,000 --> 00:03:36,990 environments that I'm using. 58 00:03:37,000 --> 00:03:39,990 And if it doesn't, then I'll make a symbolic link or something and make it work. 59 00:03:40,000 --> 00:03:41,990 So if you're running this on a Unix-based operating system, 60 00:03:42,000 --> 00:03:48,990 you'll want to do ls -l and look at the file permissions, and make sure that it has 61 00:03:49,000 --> 00:03:50,990 executable permissions. 62 00:03:51,000 --> 00:03:56,990 If it doesn't, you can make it executable by typing chmod, or as we pronounce it 63 00:03:57,000 --> 00:04:05,990 chmod 755, which makes it editable and executable for your user ID, and then 64 00:04:06,000 --> 00:04:07,990 the name of the file. 65 00:04:08,000 --> 00:04:09,990 And that will make it executable. 66 00:04:10,000 --> 00:04:15,990 And then you can execute it with ./ or however it is that you do that on your system. 67 00:04:16,000 --> 00:04:19,990 So that is the development environment that we will be using. 68 00:04:20,000 --> 00:04:22,990 For the most part, we're going to using Eclipse. 69 00:04:23,000 --> 00:04:25,990 And so we'll be running scripts like this. 70 00:04:26,000 --> 00:04:26,990 Save it and Run it. 71 00:04:27,000 --> 00:04:29,990 It'll run here in the Console. 72 00:04:30,000 --> 00:04:32,990 So you're going to want to take the opportunity, using this "Hello, World!" 73 00:04:33,000 --> 00:04:36,990 script, to learn about the development cycle and whatever environment you're 74 00:04:37,000 --> 00:04:41,990 using, especially if it's not Eclipse, to follow along with the exercises 75 00:04:42,000 --> 00:04:52,000 in this course.