1 00:00:03,969 --> 00:00:08,320 For the next part of the challenge, we need to display the options again, if the 2 00:00:08,320 --> 00:00:12,610 user enters an invalid choice. The obvious way to do that is to copy the 3 00:00:12,610 --> 00:00:17,800 print lines, from lines 1 to 7, and paste them into an else block. So let's have a 4 00:00:17,800 --> 00:00:29,360 go at doing that. I'm gonna add an else block here, and paste in those choices. 5 00:00:29,360 --> 00:00:36,420 Then I'll make sure they're obviously indented to the right level, as well. Okay 6 00:00:36,420 --> 00:00:39,670 So that should work. Let's run the program and make sure that the valid 7 00:00:39,670 --> 00:00:45,429 options still work, and then try an invalid choice. Alright, so I'm going to 8 00:00:45,429 --> 00:00:51,460 use 3 to go swimming, 4 to have dinner - that's working. Let's try an invalid 9 00:00:51,460 --> 00:00:55,839 choice, 8 - that's obviously invalid - and we're now getting the menu displaying again 10 00:00:55,840 --> 00:01:00,840 which is good. I'll enter zero, to make sure that still works, to quit the program. 11 00:01:00,840 --> 00:01:06,520 Alright so that works, but obviously it's a little bit untidy. Obviously up here, 12 00:01:06,520 --> 00:01:11,920 in the options on lines 1 to 7 but also then on lines 17 through 23. It would be a 13 00:01:11,920 --> 00:01:15,940 lot neater to only print the menu in one place. A function might be the most 14 00:01:15,940 --> 00:01:19,510 appropriate way to do that, but we haven't covered functions in the course 15 00:01:19,510 --> 00:01:23,650 yet. So this is the bit that requires some thought, and it's why we made this 16 00:01:23,650 --> 00:01:28,560 part of the challenge, optional - thinking like a programmer. 17 00:01:28,560 --> 00:01:32,340 One thing you'll find, when you learn to program, is that the way you think 18 00:01:32,340 --> 00:01:37,220 changes. It happens slowly, over time, as you work with more and more code. 19 00:01:37,220 --> 00:01:41,580 You'll automatically start looking at things in different ways, and considering different 20 00:01:41,590 --> 00:01:47,619 options to solve a given problem. So back to our code. In this example, what 21 00:01:47,619 --> 00:01:52,180 would happen if we requested the input at the end of the loop, instead of at the 22 00:01:52,180 --> 00:01:56,110 beginning, where it currently is on line 10. Well the first thing that will 23 00:01:56,110 --> 00:01:59,110 happen is, we'll get an error. So let's actually see that. So I'm going 24 00:01:59,110 --> 00:02:07,229 to take line 10. I'm going to cut that and move that down, here, to line 23. 25 00:02:07,229 --> 00:02:14,400 Actually, what I'll do is, I'll put a space there, and then I'll come up here and remove the blank line on line 10. 26 00:02:14,400 --> 00:02:18,680 Now be careful with the indentation when you move line ten, as I've just done. 27 00:02:18,680 --> 00:02:22,780 It should have the same indentation as it had before, and be at the same level as 28 00:02:22,780 --> 00:02:27,730 the if, elif and else, which you can see that it is here. Now I won't run the 29 00:02:27,730 --> 00:02:31,720 program because my IDE's showing a problem with line 10, and if I hover over the 30 00:02:31,720 --> 00:02:38,230 choice variable there, Name choice can be not defined. If your IDE doesn't highlight 31 00:02:38,230 --> 00:02:42,640 problems before you run, then run the program to actually see the error. 32 00:02:42,640 --> 00:02:47,260 Alright, so we need to define choice before the loop starts. So I'm going to come 33 00:02:47,260 --> 00:02:54,940 down here, basically, above the while, and start there. So choice equals - now we need 34 00:02:54,940 --> 00:02:58,840 to bind it to some value but what value should we use here? We know that it 35 00:02:58,840 --> 00:03:03,190 mustn't be 0 because that would cause the loop to break straight away. We also 36 00:03:03,190 --> 00:03:07,450 don't want to use one of the valid options 1 through 5. So we can initialize 37 00:03:07,450 --> 00:03:12,670 it to almost anything else, apart from the strings 1 to 5 and 0. So what I'm 38 00:03:12,670 --> 00:03:20,080 going to do is bind it to the string value - or the minus sign. So that makes 39 00:03:20,080 --> 00:03:23,340 sure that the variable exists and has a value but it doesn't have a value that 40 00:03:23,350 --> 00:03:26,859 we're likely to use in our menu. The error has obviously disappeared now, 41 00:03:26,859 --> 00:03:33,220 on line 11. Let's run the program and see what happens. So you can see, immediately, 42 00:03:33,220 --> 00:03:37,269 what's happened there, is we're now getting the menu printing out twice. So now that 43 00:03:37,269 --> 00:03:40,180 we're seeing that, we don't need lines 1 to 7 anymore, so I'm actually going to 44 00:03:40,180 --> 00:03:45,910 remove those, delete them. I'm gonna delete the blank ones as well. I'm going to rerun this 45 00:03:45,910 --> 00:03:51,579 again, and we've seen this popup before, The program is already running. We don't want to 46 00:03:51,579 --> 00:03:55,209 be typing into the old version, so I'm going to choose stop and Rerun, to run the 47 00:03:55,209 --> 00:03:58,819 latest code instead. That's looking better now, the menu's only printing 48 00:03:58,820 --> 00:04:04,320 once and we're inside the loop, waiting for input. Let's try some options here, 49 00:04:04,320 --> 00:04:11,900 so option one, Learn Python - You chose 1. Let's check the other options - 2, 3, 4, 5. 50 00:04:11,900 --> 00:04:16,480 We'll choose an invalid option. It should hopefully display the menu again, and it 51 00:04:16,488 --> 00:04:24,830 does do that, only 0 to quit. So don't worry if you struggled with this part of 52 00:04:24,830 --> 00:04:29,030 the challenge. As you read and write more code, you'll start to consider different 53 00:04:29,030 --> 00:04:33,320 ways of doing the same thing. As long as you take the time to understand how your 54 00:04:33,320 --> 00:04:37,340 code's working - and you can use the debugger to help here - you'll start to 55 00:04:37,340 --> 00:04:40,820 look at problems in different ways. Try different ways to solve a problem and 56 00:04:40,820 --> 00:04:45,560 experiment by changing code, to understand what effect each line has. 57 00:04:45,560 --> 00:04:48,860 Alright, so the final video coming up in this section will be very short. 58 00:04:48,860 --> 00:04:53,340 I'm going to use a condition on line 2, instead of while true. 59 00:04:53,340 --> 00:04:56,320 See you in the next video.