WEBVTT 00:00.140 --> 00:04.640 This is the solution for the step number one for this final project with the Raspberry Pi. 00:04.670 --> 00:09.020 Make sure you have downloaded the PDF from the last lesson, or you can make sure you have read the 00:09.020 --> 00:11.870 PDF so you know what's the challenge. 00:11.870 --> 00:17.000 And in this first step, what we want to do is to detect a movement with the Pi sensor. 00:17.000 --> 00:22.700 And when a movement has been detected for five seconds, we want to take a photo. 00:22.700 --> 00:26.540 So we're just going to do the Pir sensor part and the logic. 00:26.540 --> 00:29.330 And the photo is going to be in the next step. 00:29.330 --> 00:31.070 So let's get started. 00:31.100 --> 00:33.740 I'm going to start with a blank page. 00:33.740 --> 00:44.180 And let's import from Gpio zero import motion sensor okay let's start with this. 00:44.180 --> 00:51.650 Then we are going to initialize our Pir with this motion sensor. 00:51.650 --> 00:53.870 And that's Gpio number four. 00:53.990 --> 00:57.110 After we initialize it we can add the callbacks. 00:57.110 --> 01:05.500 So I'm going to use the callbacks here with Pir dot when Motion and then per dot. 01:05.530 --> 01:06.280 When? 01:06.280 --> 01:08.050 No motion. 01:08.320 --> 01:08.860 Okay. 01:08.860 --> 01:13.840 So I need to create a function for both callbacks here. 01:13.870 --> 01:16.600 I'm going to create the function right here. 01:17.170 --> 01:20.920 For example def motion detected. 01:22.840 --> 01:27.790 And let's create another one def motion. 01:27.790 --> 01:31.000 Let's call it motion finished okay. 01:31.030 --> 01:36.520 Because the no motion trigger here is well after motion has been detected. 01:36.520 --> 01:39.190 And then not this is going to be called. 01:39.190 --> 01:41.230 So we can call it motion finished. 01:41.230 --> 01:44.590 Let's add a column here and then let's register. 01:44.590 --> 01:47.560 So motion detected. 01:48.910 --> 01:52.030 And once again important not to put parentheses here. 01:52.030 --> 01:57.190 And motion finished okay. 01:57.190 --> 02:04.710 And just to finish this global structure I'm going to do from signal inputs pose. 02:04.710 --> 02:07.980 And then let's just do pose. 02:08.160 --> 02:08.400 Okay. 02:08.430 --> 02:13.530 So this is what we've done before in the motion sensor section we just created. 02:13.560 --> 02:17.940 Then we had two callbacks to know when the motion has been detected and when it's finished. 02:17.940 --> 02:20.760 And then we can write the logic of the code in this. 02:20.760 --> 02:22.710 And then we make sure that we pose the problem. 02:22.740 --> 02:25.050 Otherwise it's going to exit right away. 02:25.080 --> 02:32.850 Now before I write the logic here, which is going to be the main challenge, let's just add an LED 02:33.090 --> 02:38.640 and we're just going to turn on the LED when the motion is detected and turn off the LED when the motion 02:38.640 --> 02:39.780 is not detected. 02:39.810 --> 02:40.050 Okay. 02:40.080 --> 02:42.660 So it's going to be easier for us when we test the program. 02:42.660 --> 02:45.360 We can see the LED turned on or turned off. 02:45.360 --> 02:48.720 And it's going to be much easier for us to visualize what's happening. 02:48.750 --> 02:49.230 Okay. 02:49.230 --> 02:50.640 So let's just add this. 02:50.670 --> 02:51.990 And that's going to be very quick. 02:51.990 --> 02:53.790 So I add the LED here. 02:54.420 --> 02:58.230 Then I initialize my LED I just use one. 02:58.260 --> 02:58.410 Okay. 02:58.440 --> 03:00.150 You could use multiple ones if you want. 03:00.180 --> 03:01.860 But one is enough. 03:01.860 --> 03:06.410 And I'm going to use the first one for example, which is on Gpio 17. 03:06.440 --> 03:09.560 Maybe after that I can add a print here. 03:09.590 --> 03:13.280 Let's say Gpio was setup. 03:13.310 --> 03:14.030 Okay. 03:14.600 --> 03:14.810 All right. 03:14.840 --> 03:21.350 So for everything I initialize the Gpio, the camera etc. I'm going to add a print here to say that 03:21.350 --> 03:22.010 it's okay. 03:22.010 --> 03:27.410 So when we start the program if we have an error somewhere we can have a better idea of what happened. 03:27.410 --> 03:31.310 And let's just do setup Gpio. 03:31.670 --> 03:33.530 So I add a comment here okay. 03:33.560 --> 03:34.610 It's not going to be executed. 03:34.610 --> 03:38.300 It's just a comment to say this is the setup Gpio part. 03:38.330 --> 03:38.690 Great. 03:38.690 --> 03:43.490 So now when the motion is detected I can do LED dot on. 03:44.120 --> 03:48.590 And when the motion is finished I can do LED dot off. 03:48.980 --> 03:49.910 All right that's it. 03:49.910 --> 03:53.270 Now if you want you can well you can save the program already. 03:53.840 --> 03:55.730 And let's name it. 03:55.910 --> 04:01.160 So project step one dot pi. 04:02.060 --> 04:02.540 Great. 04:02.570 --> 04:04.670 Now you can go on the terminal. 04:04.670 --> 04:07.190 We're going to try to run everything from the terminal. 04:08.060 --> 04:14.120 You go to documents Python programs and you can do Python three projects. 04:14.540 --> 04:19.310 Step 1CI use the auto completion here and Gpio setup okay. 04:19.310 --> 04:26.960 And if you put your hand in front of the Pir sensor you should be able to see also the LED turned on 04:26.960 --> 04:28.160 or turned off. 04:28.190 --> 04:28.370 Okay. 04:28.400 --> 04:30.680 So you can do a quick test already. 04:30.680 --> 04:33.080 And now that we have this code structure okay. 04:33.110 --> 04:34.550 So that's already a good start. 04:34.550 --> 04:42.080 Let's add the logic to say that we want to take a photo after a motion has been detected for a minimum 04:42.110 --> 04:43.610 of five seconds. 04:43.610 --> 04:45.230 So how to do that? 04:45.230 --> 04:53.270 Well, given this callback here, this callback structure, what I can do is to start monitoring the 04:53.270 --> 04:53.600 time. 04:53.600 --> 04:56.720 So I could create kind of a timer and start the timer. 04:56.720 --> 04:59.570 When we get to the motion detected. 04:59.600 --> 05:02.960 Then I could stop the timer when we get the motion finished. 05:02.960 --> 05:09.850 And I could just compare this value of the time right now, minus the time that we registered here. 05:09.850 --> 05:12.160 Is this value greater than five seconds? 05:12.160 --> 05:14.530 If yes, we take a photo. 05:15.010 --> 05:15.310 Okay. 05:15.310 --> 05:20.590 So here with those two callbacks it's not so hard task to do as an alternative. 05:20.590 --> 05:23.830 And that's also something I'm going to talk in the conclusion of this project. 05:23.830 --> 05:28.060 You could instead of writing callbacks like that, you could use a while loop. 05:28.060 --> 05:29.500 So an infinite while loop. 05:29.500 --> 05:35.380 And the way to detect that the Pir sensor has been triggered for five seconds is going to be a tiny 05:35.380 --> 05:40.870 bit different, maybe a bit more complicated, but I'm going to leave that up to you at the end of the 05:40.870 --> 05:41.320 project. 05:41.350 --> 05:41.500 Okay? 05:41.530 --> 05:46.090 If you want to progress more and to get another challenge for this course, I'm just going to focus 05:46.090 --> 05:47.830 on that solution with the callbacks. 05:47.830 --> 05:51.730 So how to actually get the time and register the time? 05:51.730 --> 05:54.910 Well, if I'm going to run on the shell here a quick test. 05:54.910 --> 05:57.580 You can do import time first. 05:57.760 --> 06:00.610 And then if you do time dot time. 06:00.610 --> 06:04.780 So there is a time function inside the time module with the parentheses. 06:04.780 --> 06:06.030 You see we have. 06:06.390 --> 06:07.410 That's the current time. 06:07.590 --> 06:09.090 That's called the time stamp. 06:09.120 --> 06:13.680 That's the current time with some seconds and then a decimal point. 06:14.130 --> 06:16.290 If I run the time again, you can see. 06:16.290 --> 06:21.720 So it was eight something with eight seconds and now 18 seconds. 06:21.720 --> 06:26.490 So basically it was 10s duration between those two. 06:26.520 --> 06:32.820 If I do this one minus that one I will see about 10s duration. 06:32.820 --> 06:34.560 So that's what we're going to use here. 06:34.560 --> 06:40.110 I'm going to import time and then I'm going to start. 06:40.110 --> 06:45.900 So I'm going to record the time here and check the difference with this starting time in the motion 06:45.900 --> 06:46.470 finished. 06:46.470 --> 06:52.530 So to start the time here and to be able to use it there we need to create a global variable. 06:52.530 --> 06:54.780 So I'm going to create a variable here. 06:55.260 --> 06:59.220 For example I can do global variables. 06:59.250 --> 07:01.200 And we're going to put the global variables here. 07:01.200 --> 07:06.060 And let's name this one time motion started. 07:06.060 --> 07:08.600 We're gonna initialize it to the current time. 07:08.630 --> 07:10.190 Actually, time dot time. 07:10.460 --> 07:12.290 So we give it a first value. 07:12.320 --> 07:15.350 That's going to be the current time when we start the program. 07:15.350 --> 07:20.780 Then when the motion is detected, what we will do is we will do time. 07:20.930 --> 07:25.190 Motion started is equal to time dot time. 07:25.220 --> 07:25.430 Okay. 07:25.460 --> 07:28.610 So we store the current time inside this variable. 07:29.000 --> 07:35.150 And because this is a global variable you can use the global variable in a more nested scope if you're 07:35.150 --> 07:37.670 going to read this variable or just use it. 07:37.670 --> 07:41.720 But if you're going to modify it then you need to use the global keyword. 07:41.750 --> 07:42.020 Okay. 07:42.050 --> 07:44.210 So I'm going to use global time. 07:44.210 --> 07:46.370 Motion started. 07:46.370 --> 07:51.290 So this way when I do this I'm actually modifying that variable here. 07:51.290 --> 07:52.340 And then that's great. 07:52.340 --> 07:56.300 So we have the first step when the motion is detected. 07:56.300 --> 07:57.590 So that's the beginning. 07:57.590 --> 08:00.260 We start this kind of this timer. 08:00.290 --> 08:07.640 Then when the motion is finished what I will do is I will calculate the duration. 08:07.660 --> 08:11.920 So let's call that motion duration. 08:12.100 --> 08:12.430 All right. 08:12.460 --> 08:13.750 So here we talk about time. 08:13.750 --> 08:16.030 So time is the specific moment in time. 08:16.030 --> 08:18.070 So that's what time is it now. 08:18.100 --> 08:21.280 But the duration is a difference between two times. 08:21.280 --> 08:25.420 So the duration is going to be the current time at this moment. 08:25.420 --> 08:26.380 What is the current time. 08:26.380 --> 08:27.370 The current time is time. 08:27.370 --> 08:35.410 The time minus the time motion started. 08:35.410 --> 08:39.310 So this callback is going to be triggered when the motion is detected. 08:39.400 --> 08:42.400 When it's finished, this one is going to be called. 08:42.400 --> 08:47.020 We calculate the duration between the two and then we simply do. 08:47.050 --> 08:56.920 If motion duration is greater we can just use strictly greater than five. 08:56.920 --> 09:00.400 I'm going to use a decimal point here because we are comparing float numbers. 09:00.400 --> 09:05.380 So if it's greater than five seconds then I'm just going to use a print here. 09:06.190 --> 09:08.410 Taking a photo. 09:08.460 --> 09:13.050 and sending it by email. 09:13.080 --> 09:18.120 Okay, so we just have a print and then this is what we're going to do in the next few steps. 09:18.120 --> 09:20.640 But for now we just focus on the logic. 09:20.670 --> 09:26.370 And also I'm just going to put this just to make it a bit cleaner, maybe at the beginning of the program 09:26.370 --> 09:28.860 here it doesn't really matter. 09:28.890 --> 09:29.430 Great. 09:29.430 --> 09:31.110 So we can already test that. 09:31.110 --> 09:36.450 And actually to test it you can add intermediate logs to know what's happening. 09:36.450 --> 09:38.400 Because here you will see this log. 09:38.400 --> 09:42.300 But maybe it would be nice to see when we start the timer. 09:42.300 --> 09:45.960 So print here starting timer. 09:46.980 --> 09:55.860 And maybe let's print the motion duration so we can make some tests and see when we start the timer. 09:55.860 --> 09:58.410 We are also going to see the LED on at this time. 09:58.410 --> 10:02.730 And then when the LED goes off we can see also what was the duration. 10:02.730 --> 10:07.620 So let's run that and let's first save it okay with Ctrl s. 10:07.620 --> 10:11.970 So if you run from the terminal once again, make sure you save the file, because if you don't save 10:11.970 --> 10:16.380 it when you run it here, it's not going to save it automatically and you're going to run the previous 10:16.380 --> 10:16.950 version. 10:16.950 --> 10:21.570 So let's do this and I'm going to make some. 10:21.600 --> 10:28.290 So should be started okay I'm going to make some movement starting timer and make some movement. 10:28.290 --> 10:31.650 And you see I stop and it's five seconds. 10:31.650 --> 10:33.090 It says taking a photo. 10:34.170 --> 10:37.050 I make some movements for less than five seconds. 10:38.490 --> 10:38.700 Okay. 10:38.700 --> 10:40.950 So actually this one was more than five. 10:41.670 --> 10:43.170 Make a quick movement okay. 10:44.190 --> 10:45.810 And you see two seconds. 10:45.810 --> 10:47.400 We don't take a photo. 10:48.630 --> 10:52.680 What you might notice you see here I have for example one second. 10:53.850 --> 10:55.590 What you might notice is sometimes. 10:55.590 --> 10:56.910 So here I made a movement. 10:56.910 --> 10:59.820 But sometimes you might have false positives. 10:59.820 --> 11:05.160 So the Pir sensor is going to just detect a movement but there is no real movement. 11:05.160 --> 11:08.040 Or maybe you are on the side because here I'm a bit on the side. 11:08.040 --> 11:12.980 So the Pir still detects the movement, so make sure that there is nothing in front of the pillar. 11:13.010 --> 11:14.150 When you make the test. 11:14.240 --> 11:19.160 Now stop this and I'm just going to make a quick parenthesis on this pillar sensor once again to talk 11:19.160 --> 11:21.950 about the stability of the reading. 11:22.070 --> 11:22.310 Okay. 11:22.340 --> 11:27.890 It's not necessarily the most stable sensor, especially because, well, you could see a lot of noise. 11:27.890 --> 11:30.770 And this noise can happen with a lot of different things. 11:30.770 --> 11:36.860 For example, with the Wi-Fi signal that goes from, for example, your phone to the Raspberry Pi. 11:36.890 --> 11:41.660 As it's very close, it could create some noise on the Pi sensor. 11:41.660 --> 11:42.950 So the quality of the cable. 11:42.950 --> 11:48.500 So maybe if you have longer cables, good quality cables, and you put the Pir sensor quite far from 11:48.500 --> 11:55.310 the Raspberry Pi, maybe 50cm or 1m, then maybe it's going to be better then if you have too much light 11:55.310 --> 12:00.320 in your room that goes directly into the Pir could also make it less stable. 12:00.350 --> 12:05.390 Okay, if you have too many hardware components on the side and then depending on what surface you put 12:05.390 --> 12:05.600 it. 12:05.600 --> 12:11.620 So if you want to improve this part after this project, you can check for example, how to isolate 12:11.620 --> 12:18.280 better the Pir sensor with some foil, for example, and then how to add a capacitor between the sensor 12:18.280 --> 12:19.690 and the power supply. 12:19.720 --> 12:24.700 Well, there are all sorts of things you can do on the hardware side to make it more stable. 12:24.730 --> 12:26.740 Okay, I'm going to leave it like this for now. 12:26.770 --> 12:28.660 That's going to be good enough for this project. 12:28.660 --> 12:32.290 And also, anyway, you might not even use this specific sensor later. 12:32.290 --> 12:36.730 So the goal is really to do the project and not to worry too much about external things. 12:36.730 --> 12:41.980 So if you have some noise with the readings, if you have some false positives, don't worry too much 12:41.980 --> 12:42.700 about this, okay? 12:42.730 --> 12:48.910 This is just a hardware issue with this sensor and the way it's connected and the noise around this 12:48.910 --> 12:50.800 is something you can fix in the future. 12:50.800 --> 12:54.340 But for now, we're going to say that this is good enough for our project. 12:54.370 --> 12:54.790 All right. 12:54.790 --> 12:57.820 And now what I'm going to add one more thing to this step. 12:57.820 --> 13:02.710 Because here well if the motion has been detected for more than five seconds we take a photo. 13:02.710 --> 13:09.310 But I also want to limit this, to say that we only take a photo every 30s minimum. 13:09.310 --> 13:15.360 So you can only take a photo if the last time you took a photo was at least 30s ago. 13:15.360 --> 13:18.930 So we take maximum two photos per minute, okay? 13:18.960 --> 13:21.990 Otherwise, this could take a lot of photos. 13:21.990 --> 13:26.310 And you don't want to take too many because, well, it's going to take a lot of space on your Raspberry 13:26.310 --> 13:26.730 Pi. 13:26.760 --> 13:28.800 It's going to send a lot of emails, etc.. 13:28.800 --> 13:30.900 So we want to be sure to control that. 13:30.900 --> 13:36.810 And here, well, quite arbitrarily, I have decided that we're going to wait at least 30s between two 13:36.840 --> 13:37.410 photos. 13:37.410 --> 13:38.850 So how can I do that? 13:38.880 --> 13:40.860 Well, I'm going to create a new variable here. 13:41.010 --> 13:48.330 I'm going to call it last time photo taken, and I'm going to initialize it to. 13:48.360 --> 13:50.730 So this one I'm going to initialize it to zero. 13:50.760 --> 13:51.210 Why. 13:51.240 --> 13:56.370 Because for the first time when we run the program, I don't want to wait 30s before taking a photo, 13:56.400 --> 14:00.690 I want to take a photo as soon as it's ready and then wait 30s after that. 14:00.690 --> 14:03.390 So I have my variable last time photo taken. 14:03.390 --> 14:10.710 And here, if we have detected that the duration of the motion was more than five seconds inside this, 14:10.740 --> 14:11.910 if I'm going to do another. 14:11.910 --> 14:14.150 If I'm going to do time dot time. 14:14.150 --> 14:21.320 So that's the current time minus last time photo taken. 14:21.410 --> 14:27.080 If this is greater than 30s then I will take a photo. 14:27.350 --> 14:31.160 So I just add the tab here. 14:32.210 --> 14:39.290 And also I need to say last time photo taken is the current time. 14:40.820 --> 14:44.030 Okay, so this is a quite common behavior here. 14:44.030 --> 14:48.890 When you want to limit an action with a minimum duration between two actions. 14:48.890 --> 14:54.170 So when you want to do the action, you check that you have spent at least x amount of time between 14:54.170 --> 14:55.730 the last time and now. 14:55.730 --> 15:01.310 And if yes, then you store the current time as the last time and then you do the action. 15:01.340 --> 15:01.730 All right. 15:01.760 --> 15:08.090 So let's save that and let's test I'm going to run it again okay. 15:08.090 --> 15:10.220 So let's start. 15:10.250 --> 15:13.960 You see starting timer I'm going to do it for at least five seconds. 15:14.080 --> 15:15.370 I stop. 15:17.230 --> 15:17.590 Okay. 15:17.620 --> 15:19.780 And you see, for example, here I have an error. 15:19.780 --> 15:21.400 So let's go back to the program. 15:21.850 --> 15:25.960 You see with Python is that the program can start correctly and then you might have an error because 15:25.960 --> 15:29.620 of some code that is run later. 15:30.190 --> 15:33.520 And I probably made a typo here last time. 15:33.520 --> 15:34.720 Photo taken. 15:35.410 --> 15:35.680 Yes. 15:35.710 --> 15:37.030 Actually, it's not even a typo. 15:37.030 --> 15:42.910 It's just that, you see, I'm using that global variable and I didn't write global, so I'm going to 15:42.910 --> 15:46.900 write global with last time photo taken. 15:46.900 --> 15:48.550 Then I can use the global variable. 15:48.550 --> 15:50.050 So let's save. 15:51.010 --> 15:51.580 Let's run. 15:51.580 --> 15:54.880 And you can see here cannot access variable okay. 15:55.210 --> 15:57.580 Because it was a global one. 15:57.580 --> 16:01.630 So control C let's run again okay. 16:01.630 --> 16:06.010 And let's do a movement for five seconds. 16:08.830 --> 16:09.190 All right. 16:09.190 --> 16:11.080 So you see taking a photo and sending it by email. 16:11.080 --> 16:14.860 But now I'm doing another movement for at least five seconds. 16:14.890 --> 16:15.700 Okay. 16:17.650 --> 16:21.670 And you see, it's 6.5 seconds, but we don't take a photo. 16:21.730 --> 16:22.360 Okay. 16:22.990 --> 16:25.930 So I'm going to wait a few more seconds. 16:26.860 --> 16:27.100 Okay. 16:27.130 --> 16:30.040 And now I'm going to try again for more than five seconds. 16:30.040 --> 16:32.680 And it has been at least 30s. 16:32.980 --> 16:34.030 And. 16:36.160 --> 16:36.430 Okay. 16:36.460 --> 16:37.990 You can see 6.4 seconds. 16:37.990 --> 16:40.960 We take a photo and sending by email. 16:41.080 --> 16:42.940 So here we have two mechanisms. 16:42.940 --> 16:46.090 We make sure that the motion duration is at least five seconds. 16:46.090 --> 16:50.080 And we make sure that the last time we took a photo was at least 30s ago. 16:50.110 --> 16:50.470 Great. 16:50.470 --> 16:55.300 So this part of the program, this first step, this logic, was maybe the more complicated stuff we 16:55.300 --> 16:57.820 do in this project in terms of Python logic. 16:57.820 --> 17:02.890 But as you will see later, it's important that we do this first, because if we start to take photos 17:02.890 --> 17:07.900 and send them by email and we don't have that ready and correctly working, then let's say the program 17:07.900 --> 17:12.940 is taking 1000 photos in a few seconds and sending that by email. 17:12.940 --> 17:14.440 Well, you don't really want that. 17:14.470 --> 17:14.650 Okay. 17:14.680 --> 17:16.830 So we want to make sure that this is working. 17:16.830 --> 17:21.720 And then we can add the functionality to take the photo to send emails, etc.. 17:21.720 --> 17:23.250 And to quickly recap here. 17:23.250 --> 17:25.800 So we initialize some global variables. 17:25.800 --> 17:27.030 We initialize the Gpio. 17:27.210 --> 17:32.070 And then we have the two callbacks for the Pir sensor when the motion is detected. 17:32.070 --> 17:34.890 So with the one motion we start the timer. 17:34.890 --> 17:39.150 And then when the motion is not detected anymore we stop the. 17:39.180 --> 17:44.580 We don't restart the timer, but we compute the duration between the current time and the last time 17:44.580 --> 17:45.870 when we started the timer. 17:45.900 --> 17:52.500 If this is more than five seconds, we check that we haven't taken a photo in the last 30s if that's 17:52.500 --> 17:57.090 okay, then we store the current time as the last time we took a photo and we take a photo. 17:57.120 --> 17:58.950 One last thing to improve. 17:58.950 --> 18:03.420 That is, instead of hardcoding the values here, I'm going to create some variables here. 18:03.420 --> 18:06.870 And I'm going to name for example movement. 18:09.120 --> 18:13.260 Detected threshold. 18:13.380 --> 18:16.670 And note here that I am using all uppercase. 18:16.670 --> 18:17.630 So why is that. 18:17.630 --> 18:18.440 Because. 18:18.530 --> 18:24.500 So I'm going to put five because well we want to consider this as kind of a constant variable that we 18:24.500 --> 18:26.780 want to modify later on okay. 18:26.810 --> 18:29.930 So in Python you don't really have constant variables. 18:29.930 --> 18:36.500 So usually what I do is I put it all uppercase meaning that when I see this I try not to modify it later 18:36.500 --> 18:37.400 in the program. 18:37.400 --> 18:41.780 And the only way to modify is to just modify when you initialize it. 18:41.810 --> 18:42.380 Okay. 18:42.740 --> 18:54.110 So movement detected threshold and mean duration between photos 30s. 18:55.040 --> 18:55.370 All right. 18:55.370 --> 18:58.580 So let's take that and let's replace it here. 19:00.110 --> 19:04.160 And then let's take that one and replace there. 19:06.200 --> 19:06.620 Okay. 19:06.620 --> 19:10.940 And with this you can see it's even more clear okay what's happening in the code. 19:10.970 --> 19:15.080 And then you can modify the variables directly here at the beginning of the program. 19:15.110 --> 19:15.500 All right. 19:15.530 --> 19:17.570 And that's going to be it for the first step.