1 00:00:05,110 --> 00:00:11,500 In this section we looked at blocks in Python and saw how the level of indentation is crucial in determining 2 00:00:11,620 --> 00:00:14,080 which block a line of code belongs to. 3 00:00:14,080 --> 00:00:18,480 We then used if and else to test conditions and only execute blocks of code 4 00:00:18,490 --> 00:00:25,270 If those conditions were either True or False. We created more complex conditions and saw how to use elif 5 00:00:25,510 --> 00:00:32,659 to check several conditions in turn. Next, we moved on to execute blocks of code repeatedly, using loops. 6 00:00:32,800 --> 00:00:35,860 The first type of loop we used was the for statement. 7 00:00:35,860 --> 00:00:42,580 It's used to iterate through a range of values. for is used when you know in advance how many times you 8 00:00:42,580 --> 00:00:44,500 want to go around the loop. 9 00:00:44,500 --> 00:00:51,130 Next we looked at while loops. They're used to loop as long as the condition is True. while loops are generally 10 00:00:51,130 --> 00:00:58,270 used when you don't know in advance how many times the loop should execute. We covered continue and break 11 00:00:58,510 --> 00:01:04,180 to interrupt the normal flow of a for loop, and else to define a block that always executes if the loop 12 00:01:04,269 --> 00:01:06,560 finishes without break. 13 00:01:06,580 --> 00:01:12,070 So this is a different use of the else keyword to how it's used in an if statement, which is unfortunate 14 00:01:12,100 --> 00:01:20,710 and can be confusing; but that's the keyword that was chosen. A couple of videos weren't related to Python loops. 15 00:01:20,710 --> 00:01:25,890 We digressed to look at augmented assignment and why you should use it in preference to a normal assignment. 16 00:01:26,950 --> 00:01:30,130 We also discussed Pep 8, and the style of your python code. 17 00:01:31,280 --> 00:01:35,640 So we'll finish this section now with a short challenge, just to give you a chance to practise what you've 18 00:01:35,660 --> 00:01:37,360 learnt in the course so far. 19 00:01:37,460 --> 00:01:41,990 You'll have a chance to make use of the string formatting, that we covered in previous videos, as well 20 00:01:41,990 --> 00:01:45,320 as reading in input that the user types at the keyboard. 21 00:01:45,320 --> 00:01:49,900 You'll also get a chance to practise using if to execute code depending on a condition. 22 00:01:51,130 --> 00:01:56,080 So your challenge is to write a program to print a number of options, and allow the user to select an 23 00:01:56,080 --> 00:01:57,820 option from the list. 24 00:01:57,910 --> 00:02:02,880 The options should be numbered from 1 to 9, although you can use less than nine options if you want to. 25 00:02:03,130 --> 00:02:06,390 Make sure that there are at least four options. 26 00:02:06,490 --> 00:02:09,150 As an example, your program might look like the following. 27 00:02:09,190 --> 00:02:14,100 So as you can see in this example, we've got a heading at the top, we've got five options and a final option 28 00:02:14,350 --> 00:02:19,510 also added, which is zero to exit the program. So the program should continue looping, allowing the user 29 00:02:19,510 --> 00:02:26,600 to choose one of the options each time around, and the loop should only terminate when the user chooses zero. 30 00:02:26,620 --> 00:02:31,360 If the user makes a valid choice, the program should print a short message and the message should include 31 00:02:31,360 --> 00:02:36,370 the value that they typed. Don't print a different message for each choice. 32 00:02:36,370 --> 00:02:39,640 The only thing that should change is the number they typed. 33 00:02:39,640 --> 00:02:44,090 Although you could print out the description, I want to show you a much better way of doing that later. 34 00:02:44,140 --> 00:02:48,730 We're keeping this simple because there's lots of things that we still haven't covered yet. 35 00:02:48,760 --> 00:02:50,890 Now if their choice isn't one of the options in the menu, 36 00:02:50,890 --> 00:02:57,970 nothing should be printed (although you can still see their input on the screen). As an optional extra, 37 00:02:58,090 --> 00:03:01,410 modify the program so that the menu is printed again, 38 00:03:01,540 --> 00:03:03,390 If they choose an invalid option. 39 00:03:03,580 --> 00:03:04,970 Be careful with that one. 40 00:03:05,020 --> 00:03:09,970 You may start off by duplicating the code to print the menu but it's possible to write the program without 41 00:03:10,000 --> 00:03:12,560 duplicating the print lines. 42 00:03:12,880 --> 00:03:13,650 So that's the challenge. 43 00:03:13,650 --> 00:03:16,900 See how you go with that, and in the next video we'll go through the solution. 44 00:03:16,900 --> 00:03:18,040 See you in that next video.