WEBVTT 00:00.080 --> 00:03.290 This is now step five for this final project. 00:03.290 --> 00:06.980 And in this step we're going to create a new Python program. 00:07.010 --> 00:07.490 Okay. 00:07.490 --> 00:10.850 So we finished the first program here with step number four. 00:10.850 --> 00:17.240 And we're going to create a new one here where we're going to add a web server with flask. 00:17.240 --> 00:24.410 And what we want to be able to do is to show a web page and say how many photos were taken since the 00:24.410 --> 00:29.090 last time that you checked the web page, and then show the last photo. 00:29.090 --> 00:34.850 So in this step five, we're going to initialize the web page and say how many new photos were taken 00:34.850 --> 00:36.080 since you last checked. 00:36.080 --> 00:39.440 And displaying the photo is going to be the following step. 00:39.470 --> 00:39.830 All right. 00:39.830 --> 00:42.680 So let's get started with this new file. 00:42.710 --> 00:52.910 I'm gonna close that one and I'm going to save this one as as project step five dot pi. 00:54.380 --> 00:57.560 So to create a web server let's use flask. 00:57.560 --> 00:59.900 And let's first do some initialization. 00:59.900 --> 01:04.260 So from flask Import flask. 01:04.290 --> 01:13.170 Then we're going to create an app here is equal to flask uppercase with underscore underscore name and 01:13.170 --> 01:15.150 then underscore underscore. 01:15.180 --> 01:17.340 Then we're going to create the different routes. 01:17.340 --> 01:25.350 And at the end we do app dot run with host is equal to 0.0.0.0. 01:26.310 --> 01:26.550 All right. 01:26.580 --> 01:29.160 So that's the structure of our program. 01:29.820 --> 01:32.400 Then we want a homepage. 01:32.400 --> 01:35.910 So we want a simple default route. 01:35.910 --> 01:37.500 That's just going to say hello. 01:37.500 --> 01:46.140 So we do app dot route with a slash and we do a div index okay. 01:46.170 --> 01:47.730 We're not going to do anything on this one. 01:47.730 --> 01:50.670 Just return hello. 01:51.180 --> 01:52.920 And that's it for that okay. 01:52.920 --> 01:56.670 So I'm gonna save that and I can start to run it. 01:56.670 --> 02:01.800 So I'm gonna keep this one here, this terminal to run the first program. 02:01.800 --> 02:03.700 And I'm going to open a new terminal. 02:04.600 --> 02:13.060 Let's go to documents Python programs, and let's do Python three project. 02:13.090 --> 02:15.520 Step five. 02:16.300 --> 02:16.660 Okay. 02:16.690 --> 02:18.670 It's creating a web server. 02:18.700 --> 02:21.340 I do ctrl click on that one. 02:22.570 --> 02:22.990 All right. 02:22.990 --> 02:27.970 And we get to this web page you see with the IP address the port. 02:27.970 --> 02:29.470 And we see hello. 02:30.280 --> 02:36.130 So now I want to have this one slash check photos. 02:36.640 --> 02:36.820 Okay. 02:36.820 --> 02:40.150 So for now we have a 404 not found error. 02:40.180 --> 02:42.190 So we're going to add a new route. 02:42.220 --> 02:43.960 Let's go back to Thonny. 02:44.590 --> 02:54.190 And let's do app dot route slash check photos. 02:54.550 --> 02:56.770 I'm going to create a function here. 02:56.800 --> 02:59.800 Check photos like this. 02:59.830 --> 03:02.530 Okay so once again for URL you use dashes. 03:02.560 --> 03:07.520 It's better for Python functions, better to use underscores. 03:08.810 --> 03:12.200 And what do I do in this function? 03:12.230 --> 03:15.710 Well I will check the log file. 03:15.740 --> 03:15.920 Okay. 03:15.950 --> 03:17.720 Because that's where I'm going to get the information. 03:17.720 --> 03:20.360 So here is all the photos I have. 03:20.450 --> 03:23.660 And I have my photo logs dot txt okay. 03:23.690 --> 03:26.870 And in this you see I have two photos for now. 03:26.900 --> 03:27.080 Okay. 03:27.080 --> 03:28.820 That was the previous run of the program. 03:28.820 --> 03:32.330 So I'm going to check first if this file exists okay. 03:32.360 --> 03:36.410 If it doesn't exist then I'm going to say for example that no photo is available. 03:36.410 --> 03:43.460 And if it exists I'm going to open it and I'm going to count how many lines do I have so that I can 03:43.460 --> 03:49.730 say how many photos we have, and maybe also even compute the difference between the last time that 03:49.730 --> 03:50.390 we checked. 03:50.420 --> 03:52.670 Okay, so let's do that step by step. 03:52.670 --> 03:56.270 First let's add a variable here. 03:57.170 --> 04:02.690 So right here log file name. 04:02.690 --> 04:07.560 And I use it also as uppercase, so that we don't try to modify it later. 04:07.560 --> 04:13.260 And this one is going to be the same we have created in the previous program because, well, we need 04:13.260 --> 04:14.490 to read from the same file. 04:14.490 --> 04:26.340 So slash home slash pi slash photos final project and then slash photo blogs dot txt. 04:27.210 --> 04:40.410 Now the first thing I will do is check if os dot path dot exists with the log file name. 04:40.650 --> 04:47.850 So if it exists what we are going to do I'm going to put a comment for now is to count lines. 04:48.030 --> 04:51.690 If it doesn't exist, it means we don't have any photos. 04:51.690 --> 04:57.930 So I'm going to do return no photo available. 04:58.650 --> 04:58.920 All right. 04:58.920 --> 05:03.210 So we already have a case here where we're going to see no photo available. 05:03.240 --> 05:04.560 Now to count the lines. 05:04.560 --> 05:06.460 Well I first need to open the file. 05:06.460 --> 05:14.470 So let's do with open log file name with the reading permission. 05:15.190 --> 05:17.950 And then as f for the file. 05:18.040 --> 05:20.410 And there are probably different ways to do that. 05:20.410 --> 05:27.610 But I'm going to do simply for line in F okay I'm going to do a for loop to go through each line. 05:27.610 --> 05:30.520 That's also going to be useful for the next step. 05:30.520 --> 05:34.930 And then every time that I have a new line, I just increment a counter. 05:34.930 --> 05:37.000 So I will create a counter here. 05:37.030 --> 05:43.120 For example, I can do this at the beginning of the function line counter is equal to zero. 05:43.150 --> 05:51.370 So for every new line I do line counter plus equal one okay. 05:51.400 --> 05:52.900 So that's very basic. 05:52.900 --> 05:55.270 It's very basic but it works okay. 05:55.300 --> 05:57.460 So let's keep things simple for now. 05:57.490 --> 05:59.920 And then what do I want to print. 05:59.920 --> 06:05.050 So I don't want to just print how many lines we have in this file. 06:05.050 --> 06:10.220 I want to print how many new lines we have in this file since the last time that we checked. 06:10.220 --> 06:15.500 So since the last time that we requested this route. 06:15.500 --> 06:20.330 And so how to do this, we will need to keep somewhere the previous line counter. 06:20.330 --> 06:25.040 And because every time when we get this route we're going to enter the function again. 06:25.040 --> 06:28.250 But all the local variables here are going to be lost. 06:28.250 --> 06:35.810 So we need a global variable here I'm going to name it previous line counter. 06:36.950 --> 06:38.870 And let's initialize it to zero. 06:39.590 --> 06:45.080 And because I'm going to use it inside this function and I'm probably going to modify it I do global 06:46.250 --> 06:50.660 previous line counter. 06:50.660 --> 06:56.600 And what's going to be interesting for me is actually the difference between the current line counter 06:56.600 --> 06:58.340 and the previous one. 06:58.340 --> 07:00.050 So after this for loop. 07:00.050 --> 07:03.470 So here you can see the indentation is very important okay. 07:03.500 --> 07:10.650 After the for loop here actually we could even go back here because we will just open the file, count 07:10.680 --> 07:13.140 the lines, and then close the file. 07:13.140 --> 07:24.510 So right here in this indentation but still inside the if I will do difference is equal to previous 07:25.530 --> 07:26.340 line. 07:28.470 --> 07:32.910 Counter minus line counter which is the current one. 07:33.750 --> 07:44.100 And then I also need to do previous line counter is equal to line counter. 07:45.570 --> 07:45.990 Why? 07:46.020 --> 07:51.360 Because while the line counter that we read now, the next time that we're going to enter this function 07:51.360 --> 07:53.070 is going to be the previous one. 07:53.100 --> 07:57.150 And so to be able to keep this value we need to store it okay. 07:57.150 --> 08:02.640 So every time we compare with the previous one and then we save the current one as the previous one 08:02.640 --> 08:05.280 for the next run of that function. 08:05.310 --> 08:05.700 Great. 08:05.700 --> 08:16.060 And now what we can do is we can return a string that says so the difference, for example str difference. 08:18.010 --> 08:27.790 Plus new with space photos since you last checked. 08:28.750 --> 08:32.110 All right so let me recap here on what we did. 08:32.140 --> 08:34.060 So first we initialized flask. 08:34.090 --> 08:35.530 Well nothing really new. 08:35.560 --> 08:38.380 We check if this file exists. 08:38.380 --> 08:40.660 If no we say no photo available. 08:40.660 --> 08:44.500 And if yes we are going to count the lines. 08:44.500 --> 08:47.890 So let's say that we have two lines in our file. 08:47.890 --> 08:50.830 Well, and here actually it should be the opposite. 08:50.830 --> 08:56.260 And you can see it's important to review the code because you can easily check sometimes if something 08:56.260 --> 08:57.220 is not logic. 08:57.220 --> 09:05.950 So instead of doing previous minus current we're going to do the current minus previous line. 09:09.320 --> 09:09.770 Count. 09:10.040 --> 09:12.560 So let's say we have two new lines. 09:12.560 --> 09:17.750 We do two -0 because it's zero the first time. 09:17.750 --> 09:19.910 So we have the difference of two lines. 09:19.910 --> 09:22.010 And we can say we have two new photos. 09:22.010 --> 09:26.150 Since you last checked we also record the previous as the current. 09:26.150 --> 09:28.610 So now previous line counter is going to be two. 09:28.640 --> 09:33.830 And now let's say that you check again and you have three lines inside the file. 09:33.830 --> 09:35.030 So then you will do. 09:35.060 --> 09:40.400 Difference is equal to three minus the previous and the previous is two. 09:40.430 --> 09:43.910 So this time the difference is only going to be one. 09:43.940 --> 09:44.630 Okay. 09:45.050 --> 09:47.180 So let's save that. 09:47.180 --> 09:48.020 And let's see. 09:48.050 --> 09:50.870 Well let's see what we have in this folder for now. 09:51.200 --> 09:53.810 But we are not running the script. 09:54.320 --> 09:56.510 I'm gonna just open that file. 09:56.510 --> 09:59.000 So we have two photos okay. 09:59.930 --> 10:11.940 So if I run the project step five again and I go back here, you see that this should work. 10:11.940 --> 10:13.170 And actually it's working. 10:13.170 --> 10:14.970 So we find the root. 10:14.970 --> 10:19.410 But we have an internal server error which means it's probably a Python error. 10:19.410 --> 10:21.450 And we can see the Python error here. 10:21.450 --> 10:29.670 And yes name OS is not defined because I use C, I use OS but I don't import OS. 10:30.480 --> 10:33.390 So import OS. 10:33.420 --> 10:34.710 Let's save. 10:34.740 --> 10:36.780 Let's run again. 10:38.190 --> 10:38.850 Okay. 10:39.450 --> 10:40.500 Let's go back here. 10:40.530 --> 10:42.120 Let's check again. 10:42.120 --> 10:49.050 And you see we have two new photos since you last checked because we have two photos where we have two 10:49.050 --> 10:50.880 lines inside this photo logs. 10:50.880 --> 10:57.540 But now note that if I refresh again I have zero new photos. 10:57.540 --> 11:00.810 And that's normal because we have checked twice. 11:00.810 --> 11:03.180 And between the two times we didn't take any new photos. 11:03.180 --> 11:04.890 So we have zero new photos. 11:04.920 --> 11:05.310 All right. 11:05.310 --> 11:11.340 And that's the end of this step number five, which we're going to use directly for the next one.