WEBVTT 0 00:00.180 --> 00:02.340 Now for the final coding exercise, 1 00:02.370 --> 00:06.060 we're actually going to jump into a previous project that we created. 2 00:06.480 --> 00:10.230 This is the NATO alphabet project that we created a few days ago. 3 00:10.770 --> 00:12.150 And it's pretty simple. 4 00:12.300 --> 00:16.590 All it does is it takes the data that's inside this nato_phonetic_alphabet. 5 00:16.590 --> 00:17.423 csv, 6 00:17.730 --> 00:22.730 and it uses that to create a dictionary so that we have each letter as the key 7 00:25.230 --> 00:30.230 and the actual phonetic alphabet as the value for each of those keys. 8 00:32.190 --> 00:34.140 Now, if I go ahead and hit run, 9 00:35.250 --> 00:39.240 you can see that the entire phonetic alphabet dictionary is printed here 10 00:39.510 --> 00:42.570 and this is the structure of that dictionary. Now, 11 00:42.570 --> 00:47.570 the next thing it asks us is to enter a word and it takes that word and creates 12 00:49.140 --> 00:54.140 a new list using list comprehension that matches each of the letters to the 13 00:55.860 --> 01:00.420 correct phonetic alphabet. So Angela becomes Alpha November Golf Echo 14 01:00.420 --> 01:01.320 Lima Alpha. 15 01:01.680 --> 01:05.970 So you should remember all of this from creating this project a few days ago. 16 01:06.600 --> 01:06.870 Now, 17 01:06.870 --> 01:11.870 what we're going to do is we're going to update and refresh this project so that 18 01:12.780 --> 01:15.840 it's even better than before. Now, 19 01:15.870 --> 01:20.870 if you don't have access to the final project of this NATO alphabet project, 20 01:21.330 --> 01:25.110 then don't worry. Just head over to the course resources for today's lessons 21 01:25.440 --> 01:29.880 and you'll find a starting file that matches what you see here precisely. 22 01:30.990 --> 01:35.990 Now your job is to address a particular situation because we're relying on the 23 01:37.080 --> 01:39.630 user to enter a word. 24 01:40.260 --> 01:44.670 Then if they enter something that is actually not in this dictionary, 25 01:44.940 --> 01:48.010 let's say they entered just a number, 1234, 26 01:48.510 --> 01:52.740 then we will get a crash and we get a key error in this case. 27 01:53.220 --> 01:58.220 Now what we want to happen instead is for us to enter a word and we enter 28 01:58.440 --> 02:01.260 something that's complete nonsense. We hit enter. 29 02:01.410 --> 02:05.190 And it tells us that the sorry, only letters in the alphabet please. 30 02:05.520 --> 02:08.940 And then it goes back to give us that same prompt again. 31 02:09.450 --> 02:12.540 And if we keep refusing and we keep typing numbers, 32 02:12.840 --> 02:17.340 then it's going to continuously give us this feedback until we actually end up 33 02:17.370 --> 02:20.970 typing something that contains only letters in the alphabet 34 02:21.390 --> 02:24.660 and it actually generates the phonetic alphabet for us. 35 02:25.230 --> 02:29.160 This is the goal that we're trying to achieve. And in order to do this, 36 02:29.280 --> 02:32.400 you're going to have to use your skills of exception handling. 37 02:33.000 --> 02:35.160 Have a think about how you might achieve this, 38 02:35.520 --> 02:38.190 pause the video and complete this challenge. 39 02:41.520 --> 02:46.350 Now that we know what we're aiming for, the next step is to actually try to get 40 02:46.350 --> 02:50.670 there. Now we know that the part of the code that is prone to error 41 02:51.030 --> 02:54.780 or can occasionally be problematic is this line right here, 42 02:55.350 --> 03:00.070 because we're going through this phonetic dictionary and we're passing it a key and 43 03:00.070 --> 03:04.480 that key depends entirely on what the user puts into this input. 44 03:04.960 --> 03:09.760 So that means if they put something that is a number and it doesn't exist inside 45 03:09.760 --> 03:12.700 the phonetic dictionary, that's when we get our key error. 46 03:13.270 --> 03:17.500 So this is the line that we want to put behind a try block. 47 03:19.000 --> 03:19.930 Like this. 48 03:20.560 --> 03:25.560 And when we try out this line and if it actually fails and we end up with an 49 03:26.050 --> 03:28.840 exception, then we want to catch that exception. 50 03:29.140 --> 03:34.030 But we want to catch the specific exception, which is the key error. Now, 51 03:34.030 --> 03:38.470 what do we want to do when we actually have an exception when that key doesn't 52 03:38.470 --> 03:43.180 exist? Well, it means that the user entered something into the input 53 03:43.270 --> 03:46.390 that was not a letter from the alphabet. 54 03:46.930 --> 03:48.700 So we're going to give them some feedback. 55 03:48.730 --> 03:53.020 We're simply going to use a print statement to print 'Sorry, 56 03:53.080 --> 03:57.850 only letters in the alphabet please.' Hopefully that way they will learn 57 03:57.970 --> 04:02.590 and they will only write letters instead of trying to type other things like 58 04:02.590 --> 04:05.950 symbols or numbers. Now, 59 04:05.980 --> 04:09.430 if everything went well, so in the else case, 60 04:09.460 --> 04:12.430 then we actually want to print out the output list. 61 04:12.700 --> 04:14.500 Because if this line succeeded, 62 04:14.800 --> 04:19.750 then we will have that to print out to the user. Now, 63 04:19.780 --> 04:23.560 the only problem here is if we run the code as it is right now, 64 04:23.980 --> 04:27.580 we can enter a word, so let's try something that's not a word, 65 04:28.150 --> 04:31.660 and we get that feedback, but our code ends. 66 04:32.110 --> 04:37.110 So if we want our code to repeat so that we ask the user for a word again, 67 04:37.990 --> 04:42.160 then we're going to have to have some sort of mechanism like a loop or a 68 04:42.160 --> 04:44.530 function. So I think in this case, 69 04:44.530 --> 04:49.530 the best thing to do is actually to create a function which I'll call generate_ 70 04:51.310 --> 04:52.180 phonetic. 71 04:53.230 --> 04:57.550 And this function is going to contain all of this code. 72 04:58.090 --> 05:00.310 So in order to run this function, 73 05:00.400 --> 05:03.640 we of course have to call it outside of the function. 74 05:03.910 --> 05:06.580 So once the code runs down to here, 75 05:06.910 --> 05:11.110 it sees this line and it will run all the code inside this function. 76 05:11.860 --> 05:16.860 But what we also want to do is if there was the case of a key error where the user 77 05:18.400 --> 05:19.750 typed in something wrong, 78 05:20.020 --> 05:23.440 then we want to give them the opportunity to type in something again. 79 05:23.560 --> 05:26.950 So we want to be able to run this line of code again. 80 05:27.730 --> 05:32.730 The easiest way of doing that is to simply call this function right here. 81 05:33.550 --> 05:37.660 So that way, if they typed in something wrong, we give them some feedback 82 05:37.930 --> 05:40.870 and then we go to the very start of this function once again, 83 05:41.200 --> 05:44.980 and we get them to type in a new word using this input. 84 05:45.580 --> 05:50.580 And then we can see if that was valid or if it was not and deal with that 85 05:50.830 --> 05:54.220 accordingly. So now when we run our code, 86 05:54.310 --> 05:56.290 it won't generate any errors, 87 05:56.560 --> 06:01.220 but instead it gives me some feedback and tells me to enter another word. 88 06:02.300 --> 06:06.290 So this is more of a real-life implementation of error handling, 89 06:06.620 --> 06:11.620 making sure that we are validating and checking the user's inputs and addressing 90 06:12.410 --> 06:15.980 these situations ahead of time using exception handling. 91 06:17.390 --> 06:21.530 Now that we've taken a good look at exception handling, in the next lesson 92 06:21.650 --> 06:25.940 we're going to go back to our password manager project and use the skills that 93 06:25.940 --> 06:28.190 we've learned to improve it even further. 94 06:28.880 --> 06:31.280 So, for all of that and more, I'll see you on the next lesson.