WEBVTT 1 00:00:00.920 --> 00:00:02.460 Hi guys and welcome back. 2 00:00:02.460 --> 00:00:04.750 In this video we're going to look at some If statements 3 00:00:04.750 --> 00:00:07.490 with the in keyboard and also a few more examples 4 00:00:07.490 --> 00:00:09.600 so you get a bit more experience. 5 00:00:09.600 --> 00:00:13.130 Here we've got our movies watched which is a set of strings 6 00:00:13.130 --> 00:00:15.780 with the movie titles and then we're asking the user 7 00:00:15.780 --> 00:00:17.653 for a movie they've watched recently. 8 00:00:19.130 --> 00:00:23.510 We can then say user movie in movies watched 9 00:00:24.400 --> 00:00:27.140 and we can put that in an If statement. 10 00:00:27.140 --> 00:00:29.970 So again when Python reaches line four it's going 11 00:00:29.970 --> 00:00:33.010 to evaluate this Boolean and it's gonna say 12 00:00:33.010 --> 00:00:36.710 is the thing the user entered one of the elements 13 00:00:36.710 --> 00:00:38.923 of this collection, this set? 14 00:00:39.780 --> 00:00:42.960 And if it's true then it's going to evaluate this code here 15 00:00:42.960 --> 00:00:46.260 and remember we need indentation in front of this 16 00:00:46.260 --> 00:00:48.160 so that Python can tell what code 17 00:00:48.160 --> 00:00:50.550 is inside the If statement. 18 00:00:50.550 --> 00:00:52.610 So we're gonna print something like 19 00:00:52.610 --> 00:00:55.563 I've watched user movie too. 20 00:00:57.630 --> 00:01:01.523 Otherwise we can print I haven't watched that yet. 21 00:01:03.370 --> 00:01:07.500 If we run this then you can enter something like Green Book 22 00:01:07.500 --> 00:01:10.483 and it'll tell you that I've watched Green Book too. 23 00:01:11.640 --> 00:01:13.770 Of course if you enter something else 24 00:01:14.970 --> 00:01:18.120 then it'll tell you that I haven't watched that yet. 25 00:01:18.120 --> 00:01:20.400 So this is how you can use the in keyword 26 00:01:20.400 --> 00:01:24.800 in a If statement and it just worked in exactly the same way 27 00:01:24.800 --> 00:01:27.380 as it did in the last video when we were printing it out 28 00:01:27.380 --> 00:01:30.220 but now you can use it there in order to make decisions 29 00:01:30.220 --> 00:01:32.973 and potentially do different things in your programme. 30 00:01:33.830 --> 00:01:36.680 Let's work on a slightly different example. 31 00:01:36.680 --> 00:01:40.360 We're going to create now a magic number App. 32 00:01:40.360 --> 00:01:42.770 So in this application we're going to decide 33 00:01:42.770 --> 00:01:45.850 on a magic number, a hidden number from the user. 34 00:01:45.850 --> 00:01:48.270 We're going to ask the user to enter a number 35 00:01:48.270 --> 00:01:51.750 and then we are going to tell the user 36 00:01:51.750 --> 00:01:54.013 whether they got the number right or not. 37 00:01:54.990 --> 00:01:57.560 But before we do that we're going to ask the user 38 00:01:57.560 --> 00:02:00.070 whether they want to play the game or not. 39 00:02:00.070 --> 00:02:02.610 So we'll start by creating our magic number 40 00:02:02.610 --> 00:02:05.330 we'll say number equal seven. 41 00:02:05.330 --> 00:02:07.890 Then we're gonna ask the user whether they want to play. 42 00:02:07.890 --> 00:02:12.140 So we'll say user input equal input enter Y 43 00:02:13.070 --> 00:02:14.733 if you would like play. 44 00:02:16.910 --> 00:02:20.933 Now we're gonna say if user input equal equal Y, 45 00:02:22.120 --> 00:02:25.570 then we will ask them for a number. 46 00:02:25.570 --> 00:02:29.950 So we can do something like user number int of input, 47 00:02:29.950 --> 00:02:31.950 Guess our Number let's say. 48 00:02:31.950 --> 00:02:34.510 So we will ask them to guess our number, 49 00:02:34.510 --> 00:02:36.970 we will get the input that they type 50 00:02:36.970 --> 00:02:39.140 and then we will turn that into an integer 51 00:02:40.120 --> 00:02:42.310 and finally we can use another If statement here 52 00:02:42.310 --> 00:02:45.350 and say user number equal equal number 53 00:02:45.350 --> 00:02:47.650 then we will print that you guessed correctly. 54 00:02:50.530 --> 00:02:53.593 Otherwise we will print sorry it's wrong. 55 00:02:55.650 --> 00:02:58.180 So we're not using the in keyword here at all 56 00:02:58.180 --> 00:02:59.890 but there are a few things that I wanted to tell you 57 00:02:59.890 --> 00:03:01.940 about before we do that. 58 00:03:01.940 --> 00:03:05.530 The first one is that all of these lines are inside 59 00:03:05.530 --> 00:03:06.363 this If statement. 60 00:03:06.363 --> 00:03:10.690 So they will only ever potentially run if this is true. 61 00:03:10.690 --> 00:03:13.340 So if the user enters lowercase Y 62 00:03:13.340 --> 00:03:16.770 then we will start running this line number five, 63 00:03:16.770 --> 00:03:19.640 then we will move on to six and so on. 64 00:03:19.640 --> 00:03:22.970 Number six here is another If statement, 65 00:03:22.970 --> 00:03:26.620 so if this is true then we will run this line 66 00:03:26.620 --> 00:03:29.480 and now you can see that this line has two sets 67 00:03:29.480 --> 00:03:33.910 of indentation because it is both inside this If statement 68 00:03:33.910 --> 00:03:38.910 and this one so therefore we have four eight spaces in total 69 00:03:39.360 --> 00:03:41.710 in front of it so the Python can tell that 70 00:03:41.710 --> 00:03:44.173 this one belongs inside this If statement. 71 00:03:45.220 --> 00:03:47.300 Then we've got an else paired 72 00:03:47.300 --> 00:03:50.100 with this if statement in line six, 73 00:03:50.100 --> 00:03:51.900 which means that if the user number 74 00:03:51.900 --> 00:03:55.560 was not exactly correct given our magic number. 75 00:03:55.560 --> 00:03:57.730 We're going to print sorry it's wrong 76 00:03:57.730 --> 00:04:00.030 and again notice the indentation in this line. 77 00:04:00.960 --> 00:04:03.440 We can run this code and then we'll ask the user 78 00:04:03.440 --> 00:04:05.310 to enter why if they would like to play, 79 00:04:05.310 --> 00:04:07.870 so we are gonna enter Y and then we can guess the number, 80 00:04:07.870 --> 00:04:09.750 let's say seven and you can see 81 00:04:09.750 --> 00:04:12.010 that we guessed it correctly. 82 00:04:12.010 --> 00:04:14.450 Now let's start using the in keyword 83 00:04:14.450 --> 00:04:16.770 because the first thing that you may see users do 84 00:04:16.770 --> 00:04:18.780 is that they may think that because it is a computer 85 00:04:18.780 --> 00:04:21.520 or something they have to enter uppercase Y. 86 00:04:21.520 --> 00:04:24.440 It is quite common in computing to ask the user 87 00:04:24.440 --> 00:04:27.490 for uppercase letters so they might do that 88 00:04:27.490 --> 00:04:29.680 and here you can see that we don't support 89 00:04:29.680 --> 00:04:31.503 this uppercase variant. 90 00:04:32.550 --> 00:04:34.690 So there are two things you can do. 91 00:04:34.690 --> 00:04:36.120 The first one that we've already looked at 92 00:04:36.120 --> 00:04:38.150 is you can turn this into lowercase 93 00:04:38.150 --> 00:04:40.900 and that is actually the better choice of the two. 94 00:04:40.900 --> 00:04:43.650 So I would do this I would turn the users input 95 00:04:43.650 --> 00:04:44.920 into lowercase and then 96 00:04:44.920 --> 00:04:47.470 I would compare the lowercase user input 97 00:04:47.470 --> 00:04:50.970 with the lowercase character that I wanna check. 98 00:04:50.970 --> 00:04:52.140 But in some situations 99 00:04:52.140 --> 00:04:55.120 you may want different options potentially 100 00:04:55.120 --> 00:04:57.030 or you may not wanna do that exactly. 101 00:04:57.030 --> 00:04:59.250 So there is something you can do in this If statement 102 00:04:59.250 --> 00:05:03.740 which is to replace the Equal Equal for In 103 00:05:03.740 --> 00:05:08.740 and then you can have here a tuple of the two letters 104 00:05:09.440 --> 00:05:12.280 that you're willing to accept as your input. 105 00:05:12.280 --> 00:05:14.210 So what we do here is we create a tuple 106 00:05:14.210 --> 00:05:18.050 with two strings, lowercase Y and uppercase Y 107 00:05:18.050 --> 00:05:20.930 and then we're checking whether the users input 108 00:05:20.930 --> 00:05:22.840 is one of those two. 109 00:05:22.840 --> 00:05:25.503 And if it is then we will proceed. 110 00:05:26.550 --> 00:05:28.530 So this is something you could do if you were interested 111 00:05:28.530 --> 00:05:31.400 I'm just showing you that there but I would actually prefer 112 00:05:31.400 --> 00:05:33.763 to turn the users input into the lowercase. 113 00:05:34.870 --> 00:05:38.820 The second place where we could use the in keyword 114 00:05:38.820 --> 00:05:42.870 is if we wanted to give the user a hint regarding how close 115 00:05:42.870 --> 00:05:45.740 or how far they were from our magic number. 116 00:05:45.740 --> 00:05:47.410 So let's say that we wanna tell the user 117 00:05:47.410 --> 00:05:51.793 that they are off by one, if they enter six or eight. 118 00:05:53.090 --> 00:05:54.210 Here in the If statement 119 00:05:54.210 --> 00:05:57.060 after user number equal equal number, 120 00:05:57.060 --> 00:06:02.060 we're going to say elif number minus user number, 121 00:06:02.290 --> 00:06:07.290 in one and minus one we're gonna print you were off by one. 122 00:06:09.450 --> 00:06:12.210 So what this is doing is once again it's defining a tuple 123 00:06:12.210 --> 00:06:14.740 of two numbers that we're willing to accept, 124 00:06:14.740 --> 00:06:16.880 one and minus one. 125 00:06:16.880 --> 00:06:20.240 Then we'll go into subtract from our number 126 00:06:20.240 --> 00:06:21.970 which is seven the user number. 127 00:06:21.970 --> 00:06:24.280 let's say six as an example. 128 00:06:24.280 --> 00:06:26.880 Seven minus six is going to give us one 129 00:06:26.880 --> 00:06:28.880 and then it's going to check whether one 130 00:06:28.880 --> 00:06:32.780 is in this tuple which has one and minus one. 131 00:06:32.780 --> 00:06:35.540 If it is then we're gonna print that you are off by one. 132 00:06:35.540 --> 00:06:38.950 If they enter eight then we will do seven minus eight 133 00:06:38.950 --> 00:06:41.080 which is minus one and minus one 134 00:06:41.080 --> 00:06:42.910 will also be in this tuple. 135 00:06:42.910 --> 00:06:45.143 So we will also print you were off by one. 136 00:06:46.450 --> 00:06:48.430 This is something you could do and potentially 137 00:06:48.430 --> 00:06:52.050 this can be really handy if you want a longer set of values 138 00:06:52.050 --> 00:06:55.620 but for this specific situation there's also a better ways 139 00:06:55.620 --> 00:06:57.890 of doing it without the in keyword 140 00:06:57.890 --> 00:07:00.490 which is by using absolute values. 141 00:07:00.490 --> 00:07:02.393 So you can do ABS, 142 00:07:03.980 --> 00:07:06.070 of number minus user number 143 00:07:06.070 --> 00:07:08.700 and what ABS does is it gives you the absolute value 144 00:07:08.700 --> 00:07:09.533 of this argument. 145 00:07:09.533 --> 00:07:13.633 So if you pass it the value one ABS of one 146 00:07:13.633 --> 00:07:17.260 will give you one but if you pass it minus one, 147 00:07:17.260 --> 00:07:19.900 ABS of minus one will give you one. 148 00:07:19.900 --> 00:07:22.200 It will turn it back into positive. 149 00:07:22.200 --> 00:07:25.280 So now number minus user number will always give you, 150 00:07:25.280 --> 00:07:29.440 how far away the user was from our magic number 151 00:07:29.440 --> 00:07:31.130 in positive terms. 152 00:07:31.130 --> 00:07:33.793 So you can go back to say an equal equal one. 153 00:07:34.820 --> 00:07:38.410 Because this number here will always be one, two, three 154 00:07:38.410 --> 00:07:39.900 and so on. 155 00:07:39.900 --> 00:07:43.357 So if they were off by one then we can just print that. 156 00:07:43.357 --> 00:07:45.420 And I think this is a slightly better approach 157 00:07:45.420 --> 00:07:48.340 than using the in keyword but again the in keyword can 158 00:07:48.340 --> 00:07:50.500 be useful in a wide number of scenarios 159 00:07:50.500 --> 00:07:52.423 where this may not be enough. 160 00:07:53.840 --> 00:07:57.690 If we run this again you'll see that we can type Y 161 00:07:57.690 --> 00:08:00.830 to play then we can guess the number let's say eight 162 00:08:00.830 --> 00:08:03.640 and then it says that you were off by one. 163 00:08:03.640 --> 00:08:06.370 Feel free to play around with this code and change it 164 00:08:06.370 --> 00:08:08.670 and do more things with it if you'd like. 165 00:08:08.670 --> 00:08:11.270 This is a great exercise and will be good practise for you 166 00:08:11.270 --> 00:08:14.120 if you're starting to learn to code. 167 00:08:14.120 --> 00:08:15.510 Thanks for joining me in this video 168 00:08:15.510 --> 00:08:18.303 I hope it's been useful and I'll see you in the next one.