1 00:00:04,700 --> 00:00:07,760 Alright so we had a warning at the end of the last video and I just wanted to 2 00:00:07,760 --> 00:00:10,760 check whether you could pick that up. You can see there, it really gave it away when 3 00:00:10,769 --> 00:00:13,980 I hovered over it: Name guesses can be not defined, and of course if you look at the 4 00:00:13,980 --> 00:00:19,410 code, guess equals 1 should have been guesses equals 1. And of course when I 5 00:00:19,410 --> 00:00:24,570 do that, it disappears. Alright so there's that. Alright, so we've written 6 00:00:24,570 --> 00:00:28,080 the code to get the computer to guess a number we think of. Let's now see if 7 00:00:28,080 --> 00:00:34,620 it works. So we're gonna run the code, and we're thinking of a number between 1 and 8 00:00:34,620 --> 00:00:40,130 1000. The number I'm gonna be thinking of is 837, so I'm gonna press ENTER to start. 9 00:00:40,130 --> 00:00:46,110 The computers guess is 500. Now should it guess higher or lower, enter h or l or c if my 10 00:00:46,110 --> 00:00:50,780 guess was correct. Now what I'm gonna do there firstly, just add a space there, 11 00:00:50,780 --> 00:00:55,660 then what we're gonna do is just re-run this. I'm gonna stop it and run it again, because 12 00:00:55,660 --> 00:00:59,219 that's going to annoy me very quickly. Press ENTER there. Alright so that's 13 00:00:59,220 --> 00:01:04,660 better. 837 was the number we're guessing. We can see here, the computer's guessed 500. 14 00:01:04,660 --> 00:01:07,460 Should I guess, the computer's asking, should I guess higher or lower. 15 00:01:07,460 --> 00:01:11,840 Well obviously, it needs to be higher so I'm going to enter h there. This time the 16 00:01:11,850 --> 00:01:17,310 computer's guessed 750. It's still too low because their number's 857, h again in 17 00:01:17,310 --> 00:01:25,080 that case. Computers guess is 875. It needs to guess lower so we need an l there. 18 00:01:25,080 --> 00:01:30,380 Computers guess is 812 now, or 812 is obviously too low because their 19 00:01:30,380 --> 00:01:38,360 number's 837. So I need to tell it to guess higher. 843, getting closer now to 837, 20 00:01:38,360 --> 00:01:43,939 so it's actually too high. So we need to go lower. Next guess, you can see there is 21 00:01:43,939 --> 00:01:50,820 827, which needs to be higher, so I'm gonna press h there for higher. 835 now - 22 00:01:50,820 --> 00:01:57,780 it's getting close but still a bit too low. We tell it to go higher again. My guess is 839. 23 00:01:57,780 --> 00:02:00,460 l for low because it's still too high - 24 00:02:00,460 --> 00:02:04,000 our number's 837. This time you can see he's guessed it, 25 00:02:04,000 --> 00:02:08,060 837. So I'm gonna type c there, then it's correct, 26 00:02:08,060 --> 00:02:10,679 and after all that time I've been wondering, well why have we got to guess 27 00:02:10,679 --> 00:02:16,230 in 837 guesses. What have we done wrong there? Well the simple thing is that 28 00:02:16,230 --> 00:02:18,910 we've actually printed out the wrong message. If we go down and 29 00:02:18,910 --> 00:02:24,740 have a look, we're printing out guess which is the last guess, and not guesses. 30 00:02:24,740 --> 00:02:27,760 So I'm going to fix that, and we'll run it again and this time I'm going to run it 31 00:02:27,760 --> 00:02:32,880 in fast motion, just so we go through it quickly to confirm that it works then. 32 00:02:34,840 --> 00:02:39,400 Okay, so you can see the computer's now guessed 837 again, c if we're correct. 33 00:02:39,400 --> 00:02:42,840 This time we've got it in nine guesses, so we've got the correct output now that I've fixed those 34 00:02:42,840 --> 00:02:47,360 two bugs. Now it can take less than that, depending on the number you thought of, 35 00:02:47,360 --> 00:02:51,660 but it won't ever need any more than ten guesses. So try with a few more numbers to 36 00:02:51,670 --> 00:02:57,310 make sure the program seems to work okay. So this is actually quite a hard program 37 00:02:57,310 --> 00:03:01,750 to test. A simple typing error could result in the program never guessing 38 00:03:01,750 --> 00:03:05,380 correctly, and we may not detect that unless we chose a number that causes a 39 00:03:05,380 --> 00:03:08,590 problem. Now before I would be completely happy with this code, 40 00:03:08,590 --> 00:03:12,670 I'd probably test it for all possible numbers - so I'd think of each number from 1 41 00:03:12,670 --> 00:03:17,110 to 1,000 in turn. So the next 35 hours of video would be me pressing h and l, 42 00:03:17,110 --> 00:03:20,910 over and over again. Of course not - that's not a very good use of our time, 43 00:03:20,910 --> 00:03:26,590 especially when we have computers to perform repetitive tasks for us. 44 00:03:26,590 --> 00:03:30,880 So later in the course, we'll get the computer to test this code for us. But we 45 00:03:30,880 --> 00:03:35,560 need to understand about functions first, so we'll leave it till later. Now one thing 46 00:03:35,560 --> 00:03:39,819 you might want to do, is run the program in the debugger. I won't do that, but go 47 00:03:39,819 --> 00:03:43,090 ahead and do that if you want - it's a great way to learn. The reason I'm not 48 00:03:43,090 --> 00:03:45,940 going to do it here is because there's only two values that we're interested 49 00:03:45,940 --> 00:03:49,959 in, when stepping through the code. The loop already pauses each time around, 50 00:03:49,959 --> 00:03:53,980 because it waits for our input. Printing out the values of low and high is much 51 00:03:53,980 --> 00:03:58,840 easier than using the debugger, in this case. So I'm going to do that at the 52 00:03:58,840 --> 00:04:02,709 start of the loop. So just, I'm going to close the run pane and go back to 53 00:04:02,709 --> 00:04:06,940 the start of the loop, under the while statement there. Line nine, what I'm going to 54 00:04:06,940 --> 00:04:12,920 do is print parenthesis double quotes backslash t, which is a tab character, 55 00:04:12,920 --> 00:04:19,149 Guessing in the range of, left and right curly braces, to, and left and right curly 56 00:04:19,149 --> 00:04:24,260 braces again, double quotes dot format, and in parentheses low comma high, 57 00:04:24,260 --> 00:04:27,960 then we've got our two right parentheses there. So I've included a tab character, 58 00:04:27,970 --> 00:04:31,750 that's that backslash t at the start of the output. Indenting the output makes 59 00:04:31,750 --> 00:04:35,770 it easier to pick out the computers guesses, from the diagnostic information that 60 00:04:35,770 --> 00:04:40,330 we're printing. So let's run the program again now, and this time we're going to 61 00:04:40,330 --> 00:04:45,880 be using 987 as the number to guess. So I'm gonna press ENTER to start there. 62 00:04:45,880 --> 00:04:49,420 Alright, so you can see the range is there, guessing in the range of 1 to 1000. 63 00:04:49,420 --> 00:04:55,140 1987 is higher, so I'm going to press h there, and you can see it's now guessing in the range of 64 00:04:55,150 --> 00:05:03,550 501 to 1000. The next guess is 750. 1987 is higher, so the next guess, higher again. 875, 65 00:05:03,550 --> 00:05:08,590 well it still needs to be higher. 938, and number's 987, so it still needs to be 66 00:05:08,590 --> 00:05:16,600 higher. 969, higher. 985 - we're getting much closer now, but higher. At this point 67 00:05:16,600 --> 00:05:22,280 now, the computer's guessed 993. That's higher than 987 so we go lower. 68 00:05:22,280 --> 00:05:27,960 The next guess you can see is 989 and we're guessing in the range of 986 to 992. 69 00:05:27,960 --> 00:05:32,720 So scan through the output at this stage. I'm just going to scroll up a little bit, 70 00:05:32,720 --> 00:05:35,000 and you can see all the hi-low ranges 71 00:05:35,000 --> 00:05:38,900 and see how they've changed each time. So we need to go lower now because our 72 00:05:38,900 --> 00:05:44,420 number is 987, so I'm going to type l there for lower, and you can see that 73 00:05:44,420 --> 00:05:48,410 the next guess is now the correct value. So printing out information such as the 74 00:05:48,410 --> 00:05:52,460 low and high values can be a great way to help understand what code's doing. 75 00:05:52,460 --> 00:05:55,720 It's often quicker than using the debugger, and something you might want to try 76 00:05:55,730 --> 00:05:59,240 first, but with that said of course, the debugger is always available if you want 77 00:05:59,240 --> 00:06:03,410 to check things more closely. Alright, so I'm going to enter c there to say that the computer 78 00:06:03,410 --> 00:06:07,220 was correct, and you got it in nine guesses, as you can see there. I'm just going to fix 79 00:06:07,220 --> 00:06:11,680 this run pane and then close it, and we'll end the video here. 80 00:06:11,680 --> 00:06:16,040 In the next video I want to talk about something called an Augmented assignment. Now this 81 00:06:16,040 --> 00:06:20,150 may be a suggestion that you see on line 27. I'm on Windows and it doesn't pop up 82 00:06:20,150 --> 00:06:25,670 for me, but you might be, if you're on a Mac or on a Linux machine, you might be 83 00:06:25,670 --> 00:06:29,330 seeing a suggestion that the assignment can be replaced with an Augmented 84 00:06:29,330 --> 00:06:33,170 assignment. And the suggestions do vary and it may or may not appear. The bottom 85 00:06:33,170 --> 00:06:36,530 line is we're going to talk about that, and find out what that's all about 86 00:06:36,530 --> 00:06:39,310 in the next video.