WEBVTT 00:00.080 --> 00:07.100 This is the solution for the activity 11 where you have to choose which led to turn on from a web browser. 00:07.100 --> 00:09.170 So I give you the beginning of the code. 00:09.170 --> 00:11.450 So we're going to start from what we had before. 00:11.480 --> 00:14.030 I give you the beginning of the code for the route. 00:14.120 --> 00:18.890 But first things first let's initialize our LEDs. 00:18.890 --> 00:24.110 So we're going to import LED also from the Gpio zero. 00:24.950 --> 00:27.320 And then we can initialize our LEDs. 00:27.320 --> 00:30.680 We're going to do that for example just after the pushbutton. 00:30.680 --> 00:34.790 So we could do LED one two and three and then add them into a list. 00:34.790 --> 00:36.890 But let's just create a list directly. 00:36.890 --> 00:39.410 So led list is equal to. 00:39.500 --> 00:45.740 And then let's put brackets and let's initialize the LEDs directly inside the list. 00:45.740 --> 00:48.530 So LED like that with. 00:49.220 --> 00:55.730 So the first LED was on pin so on Gpio number 17 then LED. 00:55.940 --> 00:59.510 The second was on the Gpio number 27. 00:59.570 --> 01:04.380 And then we have led with 22 for the third Gpio. 01:04.410 --> 01:05.040 Great. 01:05.040 --> 01:07.890 That's going to initialize the LEDs. 01:07.890 --> 01:12.000 So that's going to initialize all of those pins to output mode. 01:12.000 --> 01:14.100 And it should be turned off. 01:14.100 --> 01:20.670 But just to be sure let's do a for loop for LED in LED list. 01:20.700 --> 01:23.580 We do LED dot off okay. 01:23.580 --> 01:24.750 So it's quite quick to do. 01:24.750 --> 01:26.760 And this we've done it already previously. 01:26.760 --> 01:27.150 Great. 01:27.180 --> 01:29.490 Now all the LEDs are initialized. 01:29.490 --> 01:32.160 So you see we initialize all the hardware here and the app. 01:32.190 --> 01:33.450 Then we create the routes. 01:33.450 --> 01:37.350 And we can use the hardware in the different functions here. 01:37.350 --> 01:39.270 And then we run the application. 01:39.270 --> 01:44.430 So let's now write the content of this switch LED function here. 01:44.460 --> 01:50.760 First thing we want to do is to validate that the LED number is correct and that the state is correct. 01:50.760 --> 01:52.620 Let's do one by one. 01:52.620 --> 01:58.050 And actually, instead of checking if it's correct, let's check if it's not correct. 01:58.050 --> 02:01.890 And if it's not correct, we're going to return an error message directly. 02:01.890 --> 02:04.950 And we're not going to go further with the function okay. 02:04.950 --> 02:06.330 So if. 02:06.330 --> 02:07.140 If what? 02:07.170 --> 02:10.560 Well, the LED number here is going to correspond to an LED. 02:10.980 --> 02:13.140 So to an index in that list. 02:13.140 --> 02:14.970 So it's not correct. 02:15.000 --> 02:19.320 First if the index is lower than zero I'm going to write this. 02:19.320 --> 02:26.100 If LED number is strictly lower than zero then it's not going to be valid. 02:26.130 --> 02:26.310 Okay. 02:26.340 --> 02:28.590 We cannot have a negative index. 02:28.590 --> 02:32.280 And I'm going to put a or so if the LED number. 02:32.280 --> 02:38.640 So if the index is lower than zero or if the index is also greater than well the last index. 02:38.640 --> 02:39.510 How to check that. 02:39.510 --> 02:49.200 Well we can use LED number greater or equal than the length of the LED list. 02:49.200 --> 02:50.250 And why is that? 02:50.250 --> 02:56.820 Because well you can see the last index actually corresponds to the length minus one okay. 02:56.850 --> 02:58.830 The length is three here. 02:58.830 --> 03:01.350 So the index is going to be zero one and two. 03:01.380 --> 03:01.620 All right. 03:01.650 --> 03:03.120 So two is the last index. 03:03.120 --> 03:04.440 If you have three. 03:04.470 --> 03:06.600 Three is out of the list. 03:07.260 --> 03:13.720 So I check checked that the LED number, if it's greater or equal than the length, then we are out 03:13.720 --> 03:15.160 of the list. 03:15.160 --> 03:22.690 So if we have one of those two conditions, we know that the index is not in the list and is not correct. 03:22.690 --> 03:30.610 So we can return, for example, wrong LED number. 03:30.610 --> 03:35.560 And why not but the number that we have provided. 03:35.560 --> 03:40.390 So I'm going to do str because it's an integer LED number. 03:40.630 --> 03:41.140 Great. 03:41.140 --> 03:46.780 So now I go back here and I know that after I pass this if okay. 03:46.810 --> 03:51.700 So if the the condition here is false, it means that the LED number is correct. 03:51.700 --> 03:54.490 I'm going to do the same thing with the state. 03:54.490 --> 03:57.580 So if and I'm going to check if the state is not correct. 03:57.580 --> 04:01.480 So we know the state must be zero or it must be one. 04:01.480 --> 04:04.030 So there are just two values to check that easily. 04:04.030 --> 04:13.840 I can do if state is different than zero and state different than one okay. 04:13.870 --> 04:16.240 And I use the end keyword here. 04:16.240 --> 04:17.770 So we just have two values. 04:17.770 --> 04:21.850 We check if it's different than that one and different than this one. 04:21.850 --> 04:25.450 Then we're going to enter the if and return an error message. 04:25.450 --> 04:27.910 For this you could have written it differently. 04:27.910 --> 04:33.970 For example, you could have said if the state is strictly lower than zero or state is strictly greater 04:33.970 --> 04:37.030 than one, then it's going to be basically the same thing. 04:37.060 --> 04:42.820 Okay, so for those validations, maybe you have come up with something that's different than me. 04:42.820 --> 04:47.290 If you have written the activity by yourself and if it works, then it's completely fine. 04:47.320 --> 04:47.530 Okay. 04:47.560 --> 04:50.350 There is not always just one solution to a problem. 04:50.350 --> 04:53.950 There are as many solutions as there are people writing a solution. 04:53.950 --> 05:02.680 So now with this I can do return and let's say state must be 0 or 1. 05:02.890 --> 05:03.550 All right. 05:03.550 --> 05:06.430 And we are done with data validation. 05:06.430 --> 05:13.150 So we know that at this point if we didn't return anything, it means that the LED number corresponds 05:13.150 --> 05:17.710 to an index in the list, and the state is either 0 or 1. 05:17.710 --> 05:22.600 So what I can do now is I can check, for example, if state is equal to. 05:23.020 --> 05:24.430 Let's start with zero. 05:24.730 --> 05:31.150 Then we want to turn off an LED and which led the one that corresponds to the index here. 05:31.150 --> 05:37.480 So I will do LED list and then put the index which is LED number here. 05:39.490 --> 05:39.730 Okay. 05:39.730 --> 05:43.210 So I get access to the element of the list which is an LED. 05:43.510 --> 05:48.700 And I do dot off and that's it. 05:48.730 --> 05:50.020 Then I can do. 05:50.050 --> 05:55.330 So I go back here I can do l if state is equal to one. 05:55.330 --> 06:00.640 And actually I don't really need to do this because if it's not zero it's going to be one. 06:00.640 --> 06:05.080 We just validated here that the state is only going to be 0 or 1. 06:05.110 --> 06:05.650 Okay. 06:05.650 --> 06:15.040 So I don't even need to write this L if I can just write else it's going to be the same LED list with 06:15.040 --> 06:18.170 We've led member. 06:20.540 --> 06:22.310 Dots on. 06:22.310 --> 06:25.640 So we turn off or we turn on the LED. 06:25.640 --> 06:28.880 And finally, let's not forget and this is quite important. 06:28.880 --> 06:30.440 That's not the end of the function. 06:30.440 --> 06:31.940 We need to return something. 06:31.940 --> 06:34.730 If we don't return anything we might get an error. 06:34.730 --> 06:36.350 So let's return. 06:36.440 --> 06:39.200 And well, we don't really need to return anything. 06:39.230 --> 06:40.580 Let's just say okay. 06:40.580 --> 06:42.980 So we return a string here. 06:42.980 --> 06:48.470 If we didn't validate the LED number, we also return a string if we didn't validate the state. 06:48.470 --> 06:54.110 And after that we return a string to say okay, so that we have performed the action and just remove 06:54.110 --> 06:57.770 the extra spaces here and let's have a last check. 06:57.770 --> 07:00.200 So we initialize stuff here. 07:00.830 --> 07:06.440 And then we have the root validation the action the return. 07:06.470 --> 07:06.890 All right. 07:06.920 --> 07:08.000 Looks good. 07:08.000 --> 07:11.300 So I'm going to save the file with Ctrl s. 07:11.300 --> 07:15.350 And now I could run it from here I'm going to choose to run it from the terminal okay. 07:15.380 --> 07:16.880 So let's go back to the terminal. 07:16.880 --> 07:22.860 And well, let's just make sure that you don't have a flask server running anywhere, okay? 07:22.890 --> 07:27.000 Because if you were still running something on the terminal, for example, and you run something on 07:27.030 --> 07:29.250 Tony, you might get an error. 07:29.280 --> 07:29.550 All right. 07:29.580 --> 07:33.630 So here I'm going to choose to only run this from the terminal. 07:33.630 --> 07:35.970 So I am in my Python programs. 07:35.970 --> 07:41.070 Let's do Python three activity 11. 07:41.190 --> 07:42.660 Let's run that. 07:42.660 --> 07:44.790 And the server is running. 07:44.790 --> 07:48.030 And to test that let's open a web browser. 07:48.060 --> 07:48.360 Okay. 07:48.390 --> 07:54.150 So I have the localhost here is going to work but also with the IP address and the port 5000. 07:54.180 --> 07:56.610 Let's just make sure it's working okay. 07:56.640 --> 07:58.410 At least the homepage is working. 07:58.410 --> 07:59.940 So the server is working. 07:59.970 --> 08:07.110 And now I'm going to add a slash LED slash I will need to give a number. 08:07.140 --> 08:15.240 Let's start with the first LED zero and then slash state and slash I need to give 0 or 1. 08:15.240 --> 08:18.000 Let's use one to turn on the first LED. 08:18.810 --> 08:20.010 So let's press enter. 08:20.010 --> 08:21.780 And let's look at what's going to happen here. 08:21.780 --> 08:25.080 You see the first LED was turned on. 08:25.380 --> 08:29.400 All right I can replace the number here with one. 08:29.400 --> 08:32.550 That's going to be the second LED because that's the index one. 08:32.970 --> 08:33.450 All right. 08:33.450 --> 08:35.400 We turn on the second LED. 08:35.640 --> 08:38.760 Let's do the same thing with two. 08:39.480 --> 08:40.410 Great. 08:40.470 --> 08:44.250 And now let's see with three for example we're going to get an error. 08:44.250 --> 08:49.110 So it's working but we get the wrong LED number three okay. 08:49.500 --> 08:54.180 Now let's say that I want to turn off the second LED. 08:54.180 --> 08:58.500 So that's going to be the index number one I do index one here. 08:58.500 --> 09:01.170 And then state zero I press enter. 09:01.170 --> 09:03.720 And you see I turn off the second LED. 09:03.990 --> 09:04.620 Great. 09:04.620 --> 09:05.970 So it's correctly working. 09:05.970 --> 09:10.680 We could turn on and off any LED that we want on the circuit. 09:10.680 --> 09:14.400 And let's just finish to verify that everything is working here. 09:14.400 --> 09:20.940 So you have seen if I put LED that's outside of the range for example ten we have an error. 09:21.060 --> 09:26.160 Let's put a negative number as well, like minus one. 09:26.880 --> 09:32.910 Well, actually you can't even put minus one here because the minus is going to be considered as a dash. 09:32.910 --> 09:35.910 So you're going to get a URL not found anyway. 09:35.910 --> 09:38.880 So let's go back to zero here okay. 09:38.910 --> 09:40.800 And then state we can have state zero. 09:40.830 --> 09:41.850 We can have state one. 09:41.880 --> 09:42.810 That's going to work. 09:42.810 --> 09:45.120 But now let's do state two. 09:45.150 --> 09:48.450 And you see state must be 0 or 1 okay. 09:48.450 --> 09:54.300 So you can see that validating the data that you get in a web server is very important okay. 09:54.330 --> 10:00.150 So you only execute an action with an input that is valid. 10:00.150 --> 10:00.570 Great. 10:00.570 --> 10:03.870 And that's the end of this activity and also the end of this section. 10:03.870 --> 10:09.150 So with what you've done here in this section with Flask and Python, you see that you can remotely 10:09.150 --> 10:12.480 control the hardware components of your Raspberry Pi. 10:12.510 --> 10:16.680 Because this while we are still running the web browser from the Raspberry Pi. 10:16.680 --> 10:19.680 But you can try the same from any other device. 10:19.680 --> 10:25.680 So computer or phone or whatever that is connected to the same network as the Raspberry Pi.