1 00:00:01,270 --> 00:00:08,350 There are currently two bugs in our program, an easy to fix one and another one which is more challenging. 2 00:00:09,620 --> 00:00:12,260 Let me explain you the first bug. 3 00:00:12,470 --> 00:00:22,640 So when the user enters a to do such as add clean the bag and they enter another one and fix the draw 4 00:00:23,810 --> 00:00:29,330 and then show that to dos, we get these to dos next to each other. 5 00:00:31,880 --> 00:00:33,320 So how do you fix this? 6 00:00:33,350 --> 00:00:37,880 Well, there is no automated way you should use your reason. 7 00:00:38,570 --> 00:00:44,210 You should know as a programmer where in the code you are currently. 8 00:00:44,420 --> 00:00:47,720 So we are adding to DOS. 9 00:00:47,720 --> 00:00:55,220 That means the bug is probably in the if condition where we check for add. 10 00:00:57,140 --> 00:01:01,910 And this one is an easier one because we know that the problem here is the brake lines. 11 00:01:01,910 --> 00:01:05,810 So we are not adding any brake lines in here. 12 00:01:05,840 --> 00:01:09,800 Therefore, to do that, you need to go here and maybe plus. 13 00:01:11,750 --> 00:01:14,810 Backslash n and that will add a brake line. 14 00:01:16,800 --> 00:01:24,090 So just delete the existing to do save the file with control as we run. 15 00:01:25,590 --> 00:01:26,370 At. 16 00:01:26,400 --> 00:01:29,100 Clean the bag at. 17 00:01:30,820 --> 00:01:36,310 Fix the driver show and the bug is fixed. 18 00:01:36,970 --> 00:01:38,470 That was the first book. 19 00:01:38,500 --> 00:01:42,640 The other book, which is more challenging to fix, is this. 20 00:01:44,010 --> 00:01:49,890 Let's suppose the user wants to add the to the item add. 21 00:01:50,940 --> 00:01:52,260 A new member. 22 00:01:52,260 --> 00:01:57,990 So they will write, add and then add a new member. 23 00:01:59,160 --> 00:02:00,420 You press enter. 24 00:02:02,660 --> 00:02:06,110 You press show and you get this successfully. 25 00:02:06,110 --> 00:02:07,610 So far so good. 26 00:02:09,680 --> 00:02:17,030 But then if the user wants to add something and perhaps instead of answering a number, they don't know 27 00:02:17,030 --> 00:02:18,730 how to use the program well. 28 00:02:18,740 --> 00:02:29,540 So what they do is they enter something like add a new member, so they aim to edit the add a new member 29 00:02:30,020 --> 00:02:33,290 to do item and they press enter. 30 00:02:35,040 --> 00:02:39,900 And what will happen actually is that if you press show now. 31 00:02:43,190 --> 00:02:46,540 A new item was added. 32 00:02:46,550 --> 00:02:48,350 Add a new member. 33 00:02:50,350 --> 00:02:52,990 So as a new member was not edited. 34 00:02:55,040 --> 00:02:56,090 But what happened? 35 00:02:56,090 --> 00:02:56,740 Actually? 36 00:02:56,750 --> 00:02:58,850 Well, I'll explain you what happened. 37 00:02:59,060 --> 00:03:03,020 So when the user enters, it's at a new member. 38 00:03:03,650 --> 00:03:07,190 What happens is that the program starts to check. 39 00:03:08,140 --> 00:03:09,250 Line by line. 40 00:03:09,250 --> 00:03:17,800 So it checks if AD is in user action, and in this case, AD is actually in the user action. 41 00:03:19,000 --> 00:03:21,640 Well, it's part of a To-Do item. 42 00:03:22,960 --> 00:03:28,040 It was not meant to be sent as a command by the user. 43 00:03:28,060 --> 00:03:29,830 It was meant as a to do item. 44 00:03:29,830 --> 00:03:32,170 But the problem is not that smart. 45 00:03:33,780 --> 00:03:39,340 So the program was able to find an ad string in the user action. 46 00:03:39,360 --> 00:03:42,690 Therefore, what it did is it added. 47 00:03:43,840 --> 00:03:47,380 That's to do in the to do list. 48 00:03:48,370 --> 00:03:54,430 So actually what it did is it got the characters after the fourth character. 49 00:03:54,430 --> 00:03:57,910 So basically zero one, two, three. 50 00:03:58,910 --> 00:04:04,660 And so then it got to the space force of four is included and everything after four. 51 00:04:04,670 --> 00:04:09,200 So that was added as a new to do. 52 00:04:10,190 --> 00:04:14,420 So as you can see, we didn't get an error for this bug. 53 00:04:14,900 --> 00:04:20,420 So these kinds of bugs are not as easy to spot as the bugs which produce errors. 54 00:04:22,070 --> 00:04:30,950 Most likely you'd find this bug after the users report an issue and then you fix the bug and you release 55 00:04:31,850 --> 00:04:36,140 the next version of the software with the bug fixed. 56 00:04:37,610 --> 00:04:42,340 So knowing where the problem is could be 90% of the work. 57 00:04:42,350 --> 00:04:45,950 So now that we know it's easier to fix it, so how do we fix it? 58 00:04:45,980 --> 00:04:48,860 Well, again, we should use our reason. 59 00:04:48,860 --> 00:04:52,460 So it sounds like it's not a good idea to check. 60 00:04:53,380 --> 00:04:57,010 For an ad command anywhere in the string. 61 00:04:58,060 --> 00:05:02,050 So that checks if ad is anywhere in the string. 62 00:05:04,030 --> 00:05:20,470 So the user action was something like AD did add a new member and add in user action returns. 63 00:05:20,470 --> 00:05:21,160 True. 64 00:05:22,720 --> 00:05:26,380 So if true, this will be executed. 65 00:05:29,080 --> 00:05:41,380 A better way of thinking of implementing this is instead of doing that we do user action starts with. 66 00:05:44,170 --> 00:05:44,830 And. 67 00:05:45,790 --> 00:05:53,140 You press that you get false because user action does not start with ad. 68 00:05:54,700 --> 00:05:59,470 If you said user action starts with edit, then you get true. 69 00:06:00,340 --> 00:06:03,470 So starts with is a string method. 70 00:06:03,490 --> 00:06:09,400 So user action is pointing to a string and starts with is a string method. 71 00:06:09,400 --> 00:06:15,100 You can check that using str you will see that starts with a similar. 72 00:06:16,830 --> 00:06:17,880 Near the end. 73 00:06:19,820 --> 00:06:20,900 So here we go. 74 00:06:22,370 --> 00:06:30,710 So that method will check if a string starts with the input the argument value provides to the methods. 75 00:06:31,670 --> 00:06:42,620 Therefore, we go back to our program now and we say if user action starts with. 76 00:06:44,770 --> 00:06:55,750 And only in that case we extract the to do from the user action and we can do the same for the other 77 00:06:55,750 --> 00:06:56,560 conditions. 78 00:06:56,560 --> 00:07:03,820 So if user action starts with show. 79 00:07:07,880 --> 00:07:11,270 And I'll do the same for these other cases. 80 00:07:12,170 --> 00:07:13,190 Here we have. 81 00:07:13,400 --> 00:07:20,630 Edit Here we have complete. 82 00:07:25,550 --> 00:07:26,600 And here we have. 83 00:07:28,670 --> 00:07:29,330 Exit. 84 00:07:31,130 --> 00:07:39,080 So now our program is more explicit, it's more accurate, and let's have a run and check if everything 85 00:07:39,080 --> 00:07:40,010 is working well. 86 00:07:40,310 --> 00:07:51,770 So ad buy a camera show and if I press edit add a new member now. 87 00:07:54,500 --> 00:07:56,090 We're going to get this error. 88 00:07:57,200 --> 00:08:00,860 So an error is better than wrong output. 89 00:08:01,010 --> 00:08:12,110 So the error of this case in this case is that in line 26, we are trying to convert this object, which 90 00:08:12,110 --> 00:08:15,380 is a string because after edit we had. 91 00:08:18,290 --> 00:08:19,670 A string of. 92 00:08:20,720 --> 00:08:28,310 The program expects a number after added so the program has trouble converting that that string to a 93 00:08:28,310 --> 00:08:30,620 number using the end function. 94 00:08:34,330 --> 00:08:42,700 So while it is better to get an error as opposed to having wrong outputs, it is still not ideal. 95 00:08:43,770 --> 00:08:47,400 To just break the program like that for the user. 96 00:08:49,890 --> 00:08:56,010 So the user is going to get confused by this error you want to make. 97 00:08:57,070 --> 00:08:59,050 This more user friendly. 98 00:09:00,040 --> 00:09:09,310 And we can do that using error handling, not error handling is a technique which helps you as a programmer 99 00:09:09,310 --> 00:09:15,650 control the error messages and this is something we will do in the next videos. 100 00:09:15,670 --> 00:09:19,750 So instead of showing this error to the user, we will do something else. 101 00:09:20,600 --> 00:09:22,250 I'll teach you that in the next video. 102 00:09:22,280 --> 00:09:22,520 See you.