WEBVTT 00:00.080 --> 00:03.170 Let's start with a very simple Python program. 00:03.350 --> 00:07.310 First of all, well, where can you write and execute Python programs? 00:07.340 --> 00:11.990 Here we will use a software that is already installed for you on the Raspberry Pi OS. 00:11.990 --> 00:14.780 And this software is called Thonny. 00:14.870 --> 00:22.940 So to find it you can just go under menu here and click on programming and you will find Thonny here. 00:22.940 --> 00:30.830 So you just click on this and this is going to open Thonny here which is a Python IDE. 00:30.980 --> 00:35.570 And IDE here means integrated development environment. 00:35.570 --> 00:38.240 So it has everything for you to develop with Python. 00:38.240 --> 00:43.940 And the first thing we are going to do here, this is a simplified mode that we have. 00:43.940 --> 00:46.070 We are going to switch to regular mode. 00:46.070 --> 00:50.660 So you click on this here you click on okay. 00:50.720 --> 00:52.670 And now you need to restart it. 00:52.670 --> 00:57.590 So let's restart programming and Thonny. 00:58.400 --> 00:58.820 Okay. 00:58.820 --> 01:04.690 Now we have the normal mode and you can keep it like that, but I'm going to increase the font size. 01:04.720 --> 01:04.990 Okay. 01:05.020 --> 01:05.710 Here you have this. 01:05.710 --> 01:11.320 Or you have the shortcut so that you can actually see what I'm doing on my screen. 01:11.350 --> 01:11.560 Okay. 01:11.590 --> 01:14.260 So I use a bigger font size. 01:15.970 --> 01:20.530 So this tool is a great tool where you can write Python code. 01:20.530 --> 01:23.290 You can save Python programs into files. 01:23.290 --> 01:27.010 And you can also run and debug your programs. 01:27.010 --> 01:32.680 It is very handy because setting up Python with the environment can be quite tricky here. 01:32.710 --> 01:35.980 Nothing to do, just open up thonny and you're good to go. 01:35.980 --> 01:40.390 So we are first going to look at the bottom part here named shell. 01:40.600 --> 01:47.230 Just if you ever close shell by mistake or if it's not here, you can simply open it again. 01:47.260 --> 01:51.520 You just go on view and then shell okay. 01:51.550 --> 01:52.690 And it's back here. 01:53.860 --> 02:00.710 This shell part is an already configured Python environment where you can simply run any Python command 02:00.710 --> 02:03.440 you want and it will be executed right away. 02:03.470 --> 02:06.740 Let's go ahead and do a basic Hello World program. 02:06.740 --> 02:10.340 So what we want to do here is simply to print some text. 02:10.370 --> 02:14.090 You can use the already existing print function. 02:14.090 --> 02:16.730 You can see syntax highlighting here okay. 02:16.760 --> 02:18.890 And you need to open and close parentheses. 02:18.890 --> 02:21.440 So print open close parentheses. 02:21.440 --> 02:24.080 And inside we're going to use double quotes. 02:24.710 --> 02:32.840 And inside those double quotes let's say hello Raspberry Pi okay so that's our Hello World program. 02:32.840 --> 02:34.370 You can press enter. 02:35.030 --> 02:38.000 And you see we have the result of that comment okay. 02:38.030 --> 02:39.590 So we have run a Python command. 02:39.590 --> 02:43.370 And the result of that command is we see hello Raspberry Pi okay. 02:43.400 --> 02:48.500 We simply asked Python to print this piece of text. 02:48.500 --> 02:50.360 So the Python interpreter. 02:50.390 --> 02:56.090 That's how Python works is going to use a Python interpreter to execute each command one by one. 02:56.090 --> 02:57.590 So here we just have one for now. 02:57.590 --> 03:02.850 So it's going to execute this command and print the result or do whatever you ask it to do. 03:02.880 --> 03:03.390 Okay. 03:03.420 --> 03:04.980 Now we are back here. 03:04.980 --> 03:08.820 You can use the up arrow if you want to go back to the previous command. 03:08.820 --> 03:11.460 So you can use the up arrow and just press enter again. 03:11.460 --> 03:14.040 And you can see that we have Hello Raspberry Pi again. 03:14.040 --> 03:17.130 Now you could create entire programs like that on the shell. 03:17.160 --> 03:22.620 But as soon as you close the shell, your program will be gone and it's not going to be very practical. 03:22.620 --> 03:28.440 So what we're going to do from now on is to write the Python programs into a file, okay? 03:28.470 --> 03:32.850 So you can save them, you can reopen them and also run those programs. 03:32.850 --> 03:38.220 And to do that, well, you simply are going to use this text editor right here. 03:38.250 --> 03:38.580 Okay. 03:38.610 --> 03:41.010 So this is the shell but this is a text editor. 03:41.010 --> 03:45.690 So I'm going to write here same thing I'm going to write the print function. 03:45.720 --> 03:49.800 I'm going to open and close the parentheses and then put double quotes. 03:49.800 --> 03:51.240 So one and two. 03:51.240 --> 03:55.230 And inside this I'm going to say hello. 03:55.230 --> 03:57.480 And I'm going to change to RPI. 03:57.510 --> 04:00.530 Now You can know that when I press enter here. 04:00.560 --> 04:01.640 Well, it doesn't do anything. 04:01.640 --> 04:03.830 It actually goes to a new line. 04:03.830 --> 04:05.780 You can see I have one and then I have two. 04:05.810 --> 04:08.180 If I press enter again I go to a new line. 04:08.180 --> 04:11.600 So this is simply what you would expect from a text editor. 04:11.600 --> 04:13.220 So how to actually run this. 04:13.220 --> 04:16.310 Well you have this play button here run current script. 04:16.310 --> 04:17.660 So we're going to run that. 04:17.660 --> 04:20.210 And you can see it's going to run here. 04:20.210 --> 04:23.870 And you see hello RPI. 04:23.870 --> 04:27.080 And if you want to run it again you just click here again. 04:27.110 --> 04:28.820 Now you can save this file. 04:28.820 --> 04:32.120 So as for now you can see it's untitled and not saved. 04:32.120 --> 04:38.180 So to save it you just go on file save or save as okay. 04:38.210 --> 04:41.210 And when you save it's going to open this. 04:41.210 --> 04:49.010 And what it looks like with my configuration it's going a bit it's a bit oversized but it's okay I still 04:49.010 --> 04:49.610 have space. 04:49.610 --> 04:56.270 I'm just gonna well I'm going to go to documents here so you could save the file any way you want. 04:56.300 --> 04:56.540 Okay. 04:56.570 --> 04:58.220 Here we are in the, uh. 04:58.220 --> 05:00.080 We're going to see this a bit more later. 05:00.080 --> 05:04.670 We are in the home directory for your user Pi, but we're going to go to documents. 05:04.760 --> 05:05.420 Okay. 05:05.450 --> 05:09.830 And in documents you may create a new a new folder. 05:09.860 --> 05:15.140 Let's name it Python underscore programs like this. 05:15.470 --> 05:18.350 And you can click on create okay. 05:18.380 --> 05:21.290 So we just save inside a folder. 05:21.290 --> 05:23.000 It doesn't really matter which one. 05:23.000 --> 05:29.330 And for the name I'm just going to name it hello Dot p y. 05:29.360 --> 05:31.190 So the name of the file is hello. 05:31.190 --> 05:34.040 And then I have the p y extension okay. 05:34.070 --> 05:35.630 Pi extension is very important. 05:35.630 --> 05:38.390 That's the extension for any Python program. 05:38.390 --> 05:41.180 Then I can press enter and it is saved. 05:41.180 --> 05:48.650 So then I can go to file um open and I can find the file again I click on escape here. 05:48.680 --> 05:49.220 Great. 05:49.220 --> 05:51.320 You can now create a Python file. 05:51.320 --> 05:52.070 You can save it. 05:52.070 --> 05:54.410 You can load it and you can run it. 05:54.410 --> 05:58.210 And what we've seen is how to print something on the screen here. 05:58.240 --> 06:03.760 Now, in this program where we only print one thing, but you could also add another print. 06:04.450 --> 06:04.810 Okay. 06:04.840 --> 06:06.490 For example test. 06:06.580 --> 06:06.790 Okay. 06:06.790 --> 06:12.700 So you write print, you open parentheses and then you write one double quotes. 06:12.700 --> 06:16.000 And then you close the double quotes and you close the parentheses. 06:16.030 --> 06:17.500 Let's play that. 06:17.680 --> 06:21.010 And you can see we have hello API in test. 06:21.010 --> 06:26.320 So we have the two pieces of text that are printed one after the other. 06:26.320 --> 06:28.660 And you can see here that the order is very important. 06:28.690 --> 06:29.200 Okay. 06:29.200 --> 06:34.540 The program is going to be executed from line one and line two, line three etc.. 06:34.570 --> 06:36.130 Or you can see here I have a red dot. 06:36.160 --> 06:39.130 If you click I'm just going to click again and remove it. 06:39.130 --> 06:41.470 So the order for the code is very important. 06:41.470 --> 06:43.750 And we're going to come back to this quite often. 06:43.750 --> 06:47.170 You can also add as you can see you can add empty lines okay. 06:47.200 --> 06:50.170 If you add empty lines it's simply not going to do anything. 06:50.200 --> 06:52.360 You see the result is the same. 06:52.390 --> 06:52.600 Okay. 06:52.630 --> 06:55.120 So an empty line is not going to be executed. 06:55.120 --> 06:57.090 So here we execute line one. 06:57.090 --> 06:59.190 And then line two and three is nothing. 06:59.190 --> 07:02.250 Then we execute line four and then five and six. 07:02.250 --> 07:03.120 There is nothing. 07:03.120 --> 07:09.900 One other functionality I want to show you right now is how to comment one line. 07:09.900 --> 07:12.600 So let's use the hash sign here. 07:12.810 --> 07:14.520 And you can see now it turns gray. 07:14.520 --> 07:20.370 When you use the hash sign it's gonna comment the line, which means that this is not going to be executed 07:20.400 --> 07:20.580 okay. 07:20.610 --> 07:25.170 It's still here on the screen, but it's not going to be executed if I run again. 07:25.170 --> 07:28.560 You can see we only have hello API. 07:28.650 --> 07:29.310 Okay. 07:29.310 --> 07:31.410 And this one is not executed. 07:31.440 --> 07:36.390 Now, if I remove this and I run again, it is executed again. 07:36.420 --> 07:36.630 Okay. 07:36.660 --> 07:42.630 So you can add a comment in order to tell Python to ignore some lines of code. 07:42.630 --> 07:43.980 And this is very useful. 07:43.980 --> 07:49.620 You can use commands a lot with Python because for example, you have some code here and you want to 07:49.650 --> 07:55.650 just ignore one part so that you can test your program without one part and then put it again. 07:55.650 --> 07:58.140 Then you don't need to remove the code entirely. 07:58.140 --> 08:03.210 You just put comment, you test the code and then you can remove the comment if needed. 08:03.240 --> 08:03.930 Okay. 08:03.930 --> 08:09.960 And you can also use comments not just for that, but just for explaining stuff in your code. 08:09.960 --> 08:16.860 So for example the next line will print text. 08:17.040 --> 08:22.740 Okay, so here it's pretty obvious, but sometimes you might want to explain a bit more what some parts 08:22.740 --> 08:28.320 of the code are doing, or to give some more information about why you did something in that way. 08:28.350 --> 08:31.530 Okay, so you can use some comments in this case. 08:31.530 --> 08:36.870 And finally, to finish with this lesson, well here we have written everything perfectly. 08:36.900 --> 08:38.100 Okay, so it works. 08:38.100 --> 08:41.910 But let's say you forget a parenthesis here. 08:41.940 --> 08:43.770 Well, first you might see some weird thing here. 08:43.800 --> 08:45.390 Okay, you can see it's all gray. 08:45.390 --> 08:50.880 But let's say I run the script, you can see that we're going to get an error because here you can see 08:51.180 --> 08:52.620 in this error we have. 08:52.620 --> 08:56.030 So the name of the file, which is this one? 08:56.090 --> 08:57.710 The number for the line. 08:57.740 --> 08:59.210 Okay, here it's line one. 08:59.210 --> 09:01.880 And then you see we have an error. 09:01.880 --> 09:06.200 So sometimes this is going to be explicit sometimes not okay. 09:06.230 --> 09:08.330 So sometimes it's easy to find the error. 09:08.330 --> 09:10.160 But it's not always obvious here. 09:10.160 --> 09:11.090 It's pretty obvious. 09:11.090 --> 09:12.980 You see we have a syntax error. 09:13.010 --> 09:15.290 The parentheses was never closed. 09:15.290 --> 09:17.570 So we know we have to close that parenthesis here. 09:17.600 --> 09:20.330 But let's say I forgot to close the quote. 09:20.330 --> 09:21.560 So I'm going to run again. 09:21.560 --> 09:23.570 And you see we have a different error here. 09:23.570 --> 09:25.460 So still on line one. 09:25.760 --> 09:26.990 Still a syntax error. 09:26.990 --> 09:31.040 But here you can see Unterminated string literal okay. 09:31.070 --> 09:33.560 So we need to finish with a quote here. 09:33.590 --> 09:40.010 Now let's say for example instead of print I just write print okay I forgot the T. 09:40.700 --> 09:43.610 If I run we have a different error here. 09:43.610 --> 09:44.840 And now you can see. 09:44.840 --> 09:47.360 So this was executed on line one. 09:47.360 --> 09:54.610 But then on line four here you can see in line four we have an error because the name print is not defined. 09:54.640 --> 09:54.850 Okay. 09:54.880 --> 10:01.600 We need to write print so you can see when you do a mistake here you will get different kinds of errors. 10:01.630 --> 10:01.840 Okay. 10:01.840 --> 10:03.250 When you run the program. 10:03.250 --> 10:06.640 And that can help you to fix the mistakes in your code. 10:06.670 --> 10:06.910 All right. 10:06.940 --> 10:08.170 Now if I run again. 10:08.380 --> 10:08.890 All good. 10:08.890 --> 10:09.220 Great. 10:09.220 --> 10:11.170 So with this, you've already seen a lot. 10:11.200 --> 10:13.000 And this is a really good first step. 10:13.000 --> 10:15.970 Now let's continue and discover variables. 10:16.870 --> 10:18.370 And just a quick parenthesis. 10:18.370 --> 10:25.030 If you have the same problem as me, if you go on file save as if you want to load and it's too big 10:25.120 --> 10:25.420 okay. 10:25.450 --> 10:26.620 Press escape. 10:26.620 --> 10:34.750 And what I found is well, it's a bit tricky, but if you quit here, the full screen, I mean, that's 10:34.750 --> 10:38.890 something that works for me if I go smaller. 10:41.530 --> 10:46.540 If I go smaller and I open again. 10:48.940 --> 10:52.480 And then I go to file save as. 10:53.740 --> 10:56.320 maybe I can guess. 10:56.320 --> 11:03.130 So somehow if you put a smaller, if you put the screen very small, you open Sony again, then you 11:03.160 --> 11:07.600 click on save as it's going to be too big and then you increase the size of the screen. 11:07.600 --> 11:10.900 Then you can get to the edges of that and that's what you want to do. 11:10.930 --> 11:14.320 You can reduce you can reduce this okay. 11:15.100 --> 11:20.290 So what I still it's still out but I can reduce it like this. 11:20.980 --> 11:23.140 And let's just click on cancel here. 11:23.140 --> 11:30.850 And now if I go to File Save as hopefully the size is the same as the one you have defined before okay. 11:30.880 --> 11:40.240 So I'm going to go back full screen F8 full screen I'm going to open Sony again okay. 11:40.270 --> 11:43.510 But whatever size I want I can put it full screen if I want to. 11:44.320 --> 11:48.220 And let's go to File Save as okay. 11:48.250 --> 11:52.720 And now I have a normal size window and the problem is solved.