1 00:00:04,180 --> 00:00:07,750 Alright, so let's look at improving the code that we've been working on, in the 2 00:00:07,750 --> 00:00:14,320 last few videos. Looking at our menu first, on lines 21 through 27. So our menu 3 00:00:14,320 --> 00:00:18,460 options can, effectively, be stored as a list, and what we can do is then iterate 4 00:00:18,460 --> 00:00:23,529 over the list, using a for loop to print out the options. So to do that, what we 5 00:00:23,529 --> 00:00:26,109 need to define a list and we'll do that right at the top of the program, 6 00:00:26,109 --> 00:00:34,000 on line one. Alright, so I'm gonna start by typing available_parts is 7 00:00:34,000 --> 00:00:40,680 equal to left square bracket double quotes computer double quote comma. 8 00:00:40,680 --> 00:00:49,620 Next line, monitor in double quotes comma, next line, double quotes keyboard double 9 00:00:49,630 --> 00:00:56,590 quote, next line mouse in double quotes comma. Next line, mouse mat in 10 00:00:56,590 --> 00:01:04,479 double quotes comma and then finally our hdmi cable in double quotes. And I'm gonna press 11 00:01:04,479 --> 00:01:10,450 ENTER to leave the square bracket, on a line by itself, on line 7. Now that 12 00:01:10,450 --> 00:01:17,340 we've done that, we can come down and have a look at our code on lines 28 through 34, 13 00:01:17,340 --> 00:01:20,320 and we can replace that with a for loop. So I'm gonna start by deleting that code 14 00:01:20,320 --> 00:01:24,580 now. Then I'm going to tab over to the same indentation level and I'm going to 15 00:01:24,580 --> 00:01:31,690 type for_part in available_parts colon, print and in 16 00:01:31,690 --> 00:01:38,290 parentheses, part. Alright, so let's run the program. 17 00:01:38,290 --> 00:01:41,260 It's still working, as you can see, so we're part of the way there. We've got the 18 00:01:41,260 --> 00:01:45,190 parts printed out but we haven't got the number. The customer's no way of knowing 19 00:01:45,190 --> 00:01:49,840 which numbers to type in. Now we could get the index of each part and add 20 00:01:49,840 --> 00:01:56,920 one to it. So what I mean is, we'll close down this program. 21 00:01:56,920 --> 00:02:00,580 So again, what I'm saying we could do here is, change the print, print 22 00:02:00,580 --> 00:02:06,119 parentheses double quotes left and right curly braces 0, then right clearly brace 23 00:02:06,119 --> 00:02:10,090 colon, and the same for 1 - left and right curly braces with a 1 in the 24 00:02:10,090 --> 00:02:14,920 middle there, double quote dot format. And then in parentheses, available underscore 25 00:02:14,920 --> 00:02:21,860 parts dot index, and in parentheses, after the index part 26 00:02:21,860 --> 00:02:27,350 and outside of the right parentheses, plus 1 comma space part, and then two 27 00:02:27,350 --> 00:02:32,450 right parentheses to finish the line. So we could do that. What I've done there is, 28 00:02:32,450 --> 00:02:35,750 I've used string formatting and replacement fields there, to display the 29 00:02:35,750 --> 00:02:39,740 index number and the part, and I'm adding one to the index, and that's because 30 00:02:39,740 --> 00:02:43,910 indexes start at zero. We want the first number to be number one on the screen, 31 00:02:43,910 --> 00:02:49,670 rather than number zero. So let's run the program to see that it works, and you can 32 00:02:49,670 --> 00:02:53,780 see that the menu's appearing now, with numbers. Now you may get a dialog saying 33 00:02:53,780 --> 00:02:57,230 that buy.computer's not allowed to run in parallel, if you didn't exit when you 34 00:02:57,230 --> 00:03:01,160 last ran. You saw that I closed down the program. And again, you've seen it a few 35 00:03:01,160 --> 00:03:04,400 times - just click stop and rerun to run the latest version, if you get that 36 00:03:04,400 --> 00:03:08,570 dialog. But getting back to our code - that looks good, and if we add new items to a 37 00:03:08,570 --> 00:03:14,330 list, they should automatically appear in the menu. Let's try that. I'll exit out of 38 00:03:14,330 --> 00:03:22,880 the program. So let's add another item here. We'll add a dvd drive - dvd drive and 39 00:03:22,880 --> 00:03:28,900 I need to add a comma on the previous line, and now if I run the program, 40 00:03:28,900 --> 00:03:30,620 I've only changed it in one place. Notice 41 00:03:30,620 --> 00:03:36,580 that the dvd drive is appearing as option 7. Now looking at the code, 42 00:03:38,590 --> 00:03:44,270 we still need to change this code - the code on lines 15 through 26 - and we're going 43 00:03:44,270 --> 00:03:47,740 to do that soon. Before we do that, though, I want to show you a better way 44 00:03:47,740 --> 00:03:53,360 of writing lines 29 and 30. What we've done there isn't very efficient, and that's 45 00:03:53,360 --> 00:03:57,530 because Python has to look up each item in the list, in order to get its index 46 00:03:57,530 --> 00:04:01,550 position. And that's not very efficient, especially if you start dealing with 47 00:04:01,550 --> 00:04:06,140 huge lists. Index can be useful, but if you see it being used in a for loop 48 00:04:06,140 --> 00:04:10,010 like we're doing, then there's a much more efficient way, and we'll see what 49 00:04:10,010 --> 00:04:13,390 that is in the next video.