1 1 00:00:00,920 --> 00:00:02,460 Hi guys and welcome back. 2 2 00:00:02,460 --> 00:00:04,750 In this video we're going to look at some If statements 3 3 00:00:04,750 --> 00:00:07,490 with the in keyboard and also a few more examples 4 4 00:00:07,490 --> 00:00:09,600 so you get a bit more experience. 5 5 00:00:09,600 --> 00:00:13,130 Here we've got our movies watched which is a set of strings 6 6 00:00:13,130 --> 00:00:15,780 with the movie titles and then we're asking the user 7 7 00:00:15,780 --> 00:00:17,653 for a movie they've watched recently. 8 8 00:00:19,130 --> 00:00:23,510 We can then say user movie in movies watched 9 9 00:00:24,400 --> 00:00:27,140 and we can put that in an If statement. 10 10 00:00:27,140 --> 00:00:29,970 So again when Python reaches line four it's going 11 11 00:00:29,970 --> 00:00:33,010 to evaluate this Boolean and it's gonna say 12 12 00:00:33,010 --> 00:00:36,710 is the thing the user entered one of the elements 13 13 00:00:36,710 --> 00:00:38,923 of this collection, this set? 14 14 00:00:39,780 --> 00:00:42,960 And if it's true then it's going to evaluate this code here 15 15 00:00:42,960 --> 00:00:46,260 and remember we need indentation in front of this 16 16 00:00:46,260 --> 00:00:48,160 so that Python can tell what code 17 17 00:00:48,160 --> 00:00:50,550 is inside the If statement. 18 18 00:00:50,550 --> 00:00:52,610 So we're gonna print something like 19 19 00:00:52,610 --> 00:00:55,563 I've watched user movie too. 20 20 00:00:57,630 --> 00:01:01,523 Otherwise we can print I haven't watched that yet. 21 21 00:01:03,370 --> 00:01:07,500 If we run this then you can enter something like Green Book 22 22 00:01:07,500 --> 00:01:10,483 and it'll tell you that I've watched Green Book too. 23 23 00:01:11,640 --> 00:01:13,770 Of course if you enter something else 24 24 00:01:14,970 --> 00:01:18,120 then it'll tell you that I haven't watched that yet. 25 25 00:01:18,120 --> 00:01:20,400 So this is how you can use the in keyword 26 26 00:01:20,400 --> 00:01:24,800 in a If statement and it just worked in exactly the same way 27 27 00:01:24,800 --> 00:01:27,380 as it did in the last video when we were printing it out 28 28 00:01:27,380 --> 00:01:30,220 but now you can use it there in order to make decisions 29 29 00:01:30,220 --> 00:01:32,973 and potentially do different things in your programme. 30 30 00:01:33,830 --> 00:01:36,680 Let's work on a slightly different example. 31 31 00:01:36,680 --> 00:01:40,360 We're going to create now a magic number App. 32 32 00:01:40,360 --> 00:01:42,770 So in this application we're going to decide 33 33 00:01:42,770 --> 00:01:45,850 on a magic number, a hidden number from the user. 34 34 00:01:45,850 --> 00:01:48,270 We're going to ask the user to enter a number 35 35 00:01:48,270 --> 00:01:51,750 and then we are going to tell the user 36 36 00:01:51,750 --> 00:01:54,013 whether they got the number right or not. 37 37 00:01:54,990 --> 00:01:57,560 But before we do that we're going to ask the user 38 38 00:01:57,560 --> 00:02:00,070 whether they want to play the game or not. 39 39 00:02:00,070 --> 00:02:02,610 So we'll start by creating our magic number 40 40 00:02:02,610 --> 00:02:05,330 we'll say number equal seven. 41 41 00:02:05,330 --> 00:02:07,890 Then we're gonna ask the user whether they want to play. 42 42 00:02:07,890 --> 00:02:12,140 So we'll say user input equal input enter Y 43 43 00:02:13,070 --> 00:02:14,733 if you would like play. 44 44 00:02:16,910 --> 00:02:20,933 Now we're gonna say if user input equal equal Y, 45 45 00:02:22,120 --> 00:02:25,570 then we will ask them for a number. 46 46 00:02:25,570 --> 00:02:29,950 So we can do something like user number int of input, 47 47 00:02:29,950 --> 00:02:31,950 Guess our Number let's say. 48 48 00:02:31,950 --> 00:02:34,510 So we will ask them to guess our number, 49 49 00:02:34,510 --> 00:02:36,970 we will get the input that they type 50 50 00:02:36,970 --> 00:02:39,140 and then we will turn that into an integer 51 51 00:02:40,120 --> 00:02:42,310 and finally we can use another If statement here 52 52 00:02:42,310 --> 00:02:45,350 and say user number equal equal number 53 53 00:02:45,350 --> 00:02:47,650 then we will print that you guessed correctly. 54 54 00:02:50,530 --> 00:02:53,593 Otherwise we will print sorry it's wrong. 55 55 00:02:55,650 --> 00:02:58,180 So we're not using the in keyword here at all 56 56 00:02:58,180 --> 00:02:59,890 but there are a few things that I wanted to tell you 57 57 00:02:59,890 --> 00:03:01,940 about before we do that. 58 58 00:03:01,940 --> 00:03:05,530 The first one is that all of these lines are inside 59 59 00:03:05,530 --> 00:03:06,363 this If statement. 60 60 00:03:06,363 --> 00:03:10,690 So they will only ever potentially run if this is true. 61 61 00:03:10,690 --> 00:03:13,340 So if the user enters lowercase Y 62 62 00:03:13,340 --> 00:03:16,770 then we will start running this line number five, 63 63 00:03:16,770 --> 00:03:19,640 then we will move on to six and so on. 64 64 00:03:19,640 --> 00:03:22,970 Number six here is another If statement, 65 65 00:03:22,970 --> 00:03:26,620 so if this is true then we will run this line 66 66 00:03:26,620 --> 00:03:29,480 and now you can see that this line has two sets 67 67 00:03:29,480 --> 00:03:33,910 of indentation because it is both inside this If statement 68 68 00:03:33,910 --> 00:03:38,910 and this one so therefore we have four eight spaces in total 69 69 00:03:39,360 --> 00:03:41,710 in front of it so the Python can tell that 70 70 00:03:41,710 --> 00:03:44,173 this one belongs inside this If statement. 71 71 00:03:45,220 --> 00:03:47,300 Then we've got an else paired 72 72 00:03:47,300 --> 00:03:50,100 with this if statement in line six, 73 73 00:03:50,100 --> 00:03:51,900 which means that if the user number 74 74 00:03:51,900 --> 00:03:55,560 was not exactly correct given our magic number. 75 75 00:03:55,560 --> 00:03:57,730 We're going to print sorry it's wrong 76 76 00:03:57,730 --> 00:04:00,030 and again notice the indentation in this line. 77 77 00:04:00,960 --> 00:04:03,440 We can run this code and then we'll ask the user 78 78 00:04:03,440 --> 00:04:05,310 to enter why if they would like to play, 79 79 00:04:05,310 --> 00:04:07,870 so we are gonna enter Y and then we can guess the number, 80 80 00:04:07,870 --> 00:04:09,750 let's say seven and you can see 81 81 00:04:09,750 --> 00:04:12,010 that we guessed it correctly. 82 82 00:04:12,010 --> 00:04:14,450 Now let's start using the in keyword 83 83 00:04:14,450 --> 00:04:16,770 because the first thing that you may see users do 84 84 00:04:16,770 --> 00:04:18,780 is that they may think that because it is a computer 85 85 00:04:18,780 --> 00:04:21,520 or something they have to enter uppercase Y. 86 86 00:04:21,520 --> 00:04:24,440 It is quite common in computing to ask the user 87 87 00:04:24,440 --> 00:04:27,490 for uppercase letters so they might do that 88 88 00:04:27,490 --> 00:04:29,680 and here you can see that we don't support 89 89 00:04:29,680 --> 00:04:31,503 this uppercase variant. 90 90 00:04:32,550 --> 00:04:34,690 So there are two things you can do. 91 91 00:04:34,690 --> 00:04:36,120 The first one that we've already looked at 92 92 00:04:36,120 --> 00:04:38,150 is you can turn this into lowercase 93 93 00:04:38,150 --> 00:04:40,900 and that is actually the better choice of the two. 94 94 00:04:40,900 --> 00:04:43,650 So I would do this I would turn the users input 95 95 00:04:43,650 --> 00:04:44,920 into lowercase and then 96 96 00:04:44,920 --> 00:04:47,470 I would compare the lowercase user input 97 97 00:04:47,470 --> 00:04:50,970 with the lowercase character that I wanna check. 98 98 00:04:50,970 --> 00:04:52,140 But in some situations 99 99 00:04:52,140 --> 00:04:55,120 you may want different options potentially 100 100 00:04:55,120 --> 00:04:57,030 or you may not wanna do that exactly. 101 101 00:04:57,030 --> 00:04:59,250 So there is something you can do in this If statement 102 102 00:04:59,250 --> 00:05:03,740 which is to replace the Equal Equal for In 103 103 00:05:03,740 --> 00:05:08,740 and then you can have here a tuple of the two letters 104 104 00:05:09,440 --> 00:05:12,280 that you're willing to accept as your input. 105 105 00:05:12,280 --> 00:05:14,210 So what we do here is we create a tuple 106 106 00:05:14,210 --> 00:05:18,050 with two strings, lowercase Y and uppercase Y 107 107 00:05:18,050 --> 00:05:20,930 and then we're checking whether the users input 108 108 00:05:20,930 --> 00:05:22,840 is one of those two. 109 109 00:05:22,840 --> 00:05:25,503 And if it is then we will proceed. 110 110 00:05:26,550 --> 00:05:28,530 So this is something you could do if you were interested 111 111 00:05:28,530 --> 00:05:31,400 I'm just showing you that there but I would actually prefer 112 112 00:05:31,400 --> 00:05:33,763 to turn the users input into the lowercase. 113 113 00:05:34,870 --> 00:05:38,820 The second place where we could use the in keyword 114 114 00:05:38,820 --> 00:05:42,870 is if we wanted to give the user a hint regarding how close 115 115 00:05:42,870 --> 00:05:45,740 or how far they were from our magic number. 116 116 00:05:45,740 --> 00:05:47,410 So let's say that we wanna tell the user 117 117 00:05:47,410 --> 00:05:51,793 that they are off by one, if they enter six or eight. 118 118 00:05:53,090 --> 00:05:54,210 Here in the If statement 119 119 00:05:54,210 --> 00:05:57,060 after user number equal equal number, 120 120 00:05:57,060 --> 00:06:02,060 we're going to say elif number minus user number, 121 121 00:06:02,290 --> 00:06:07,290 in one and minus one we're gonna print you were off by one. 122 122 00:06:09,450 --> 00:06:12,210 So what this is doing is once again it's defining a tuple 123 123 00:06:12,210 --> 00:06:14,740 of two numbers that we're willing to accept, 124 124 00:06:14,740 --> 00:06:16,880 one and minus one. 125 125 00:06:16,880 --> 00:06:20,240 Then we'll go into subtract from our number 126 126 00:06:20,240 --> 00:06:21,970 which is seven the user number. 127 127 00:06:21,970 --> 00:06:24,280 let's say six as an example. 128 128 00:06:24,280 --> 00:06:26,880 Seven minus six is going to give us one 129 129 00:06:26,880 --> 00:06:28,880 and then it's going to check whether one 130 130 00:06:28,880 --> 00:06:32,780 is in this tuple which has one and minus one. 131 131 00:06:32,780 --> 00:06:35,540 If it is then we're gonna print that you are off by one. 132 132 00:06:35,540 --> 00:06:38,950 If they enter eight then we will do seven minus eight 133 133 00:06:38,950 --> 00:06:41,080 which is minus one and minus one 134 134 00:06:41,080 --> 00:06:42,910 will also be in this tuple. 135 135 00:06:42,910 --> 00:06:45,143 So we will also print you were off by one. 136 136 00:06:46,450 --> 00:06:48,430 This is something you could do and potentially 137 137 00:06:48,430 --> 00:06:52,050 this can be really handy if you want a longer set of values 138 138 00:06:52,050 --> 00:06:55,620 but for this specific situation there's also a better ways 139 139 00:06:55,620 --> 00:06:57,890 of doing it without the in keyword 140 140 00:06:57,890 --> 00:07:00,490 which is by using absolute values. 141 141 00:07:00,490 --> 00:07:02,393 So you can do ABS, 142 142 00:07:03,980 --> 00:07:06,070 of number minus user number 143 143 00:07:06,070 --> 00:07:08,700 and what ABS does is it gives you the absolute value 144 144 00:07:08,700 --> 00:07:09,533 of this argument. 145 145 00:07:09,533 --> 00:07:13,633 So if you pass it the value one ABS of one 146 146 00:07:13,633 --> 00:07:17,260 will give you one but if you pass it minus one, 147 147 00:07:17,260 --> 00:07:19,900 ABS of minus one will give you one. 148 148 00:07:19,900 --> 00:07:22,200 It will turn it back into positive. 149 149 00:07:22,200 --> 00:07:25,280 So now number minus user number will always give you, 150 150 00:07:25,280 --> 00:07:29,440 how far away the user was from our magic number 151 151 00:07:29,440 --> 00:07:31,130 in positive terms. 152 152 00:07:31,130 --> 00:07:33,793 So you can go back to say an equal equal one. 153 153 00:07:34,820 --> 00:07:38,410 Because this number here will always be one, two, three 154 154 00:07:38,410 --> 00:07:39,900 and so on. 155 155 00:07:39,900 --> 00:07:43,357 So if they were off by one then we can just print that. 156 156 00:07:43,357 --> 00:07:45,420 And I think this is a slightly better approach 157 157 00:07:45,420 --> 00:07:48,340 than using the in keyword but again the in keyword can 158 158 00:07:48,340 --> 00:07:50,500 be useful in a wide number of scenarios 159 159 00:07:50,500 --> 00:07:52,423 where this may not be enough. 160 160 00:07:53,840 --> 00:07:57,690 If we run this again you'll see that we can type Y 161 161 00:07:57,690 --> 00:08:00,830 to play then we can guess the number let's say eight 162 162 00:08:00,830 --> 00:08:03,640 and then it says that you were off by one. 163 163 00:08:03,640 --> 00:08:06,370 Feel free to play around with this code and change it 164 164 00:08:06,370 --> 00:08:08,670 and do more things with it if you'd like. 165 165 00:08:08,670 --> 00:08:11,270 This is a great exercise and will be good practise for you 166 166 00:08:11,270 --> 00:08:14,120 if you're starting to learn to code. 167 167 00:08:14,120 --> 00:08:15,510 Thanks for joining me in this video 168 168 00:08:15,510 --> 00:08:18,303 I hope it's been useful and I'll see you in the next one.