1 1 00:00:00,234 --> 00:00:01,940 Hi guys, and welcome back! 2 2 00:00:01,940 --> 00:00:04,700 In this video, we'll learn about getting user input 3 3 00:00:04,700 --> 00:00:05,910 so that we can get some data 4 4 00:00:05,910 --> 00:00:08,783 from our users and use it in our programmes. 5 5 00:00:09,700 --> 00:00:12,200 Let's start off by asking the user for their name, 6 6 00:00:12,200 --> 00:00:13,510 so we can print it out. 7 7 00:00:13,510 --> 00:00:16,410 We will say name equals, and again, 8 8 00:00:16,410 --> 00:00:18,360 this is us defining a variable. 9 9 00:00:18,360 --> 00:00:20,390 Now, we have to tell the variable what its 10 10 00:00:20,390 --> 00:00:21,800 value is going to be. 11 11 00:00:21,800 --> 00:00:23,620 So what we're gonna do here is we're going to 12 12 00:00:23,620 --> 00:00:26,630 ask the user for their name. 13 13 00:00:26,630 --> 00:00:28,690 And the way we do that in Python is we type, 14 14 00:00:28,690 --> 00:00:30,820 input, then a pair of brackets, 15 15 00:00:30,820 --> 00:00:33,680 and inside the brackets we are gonna type a question 16 16 00:00:33,680 --> 00:00:36,200 that we'll ask the user or a prompt. 17 17 00:00:36,200 --> 00:00:40,710 So here, goes a string where we put enter your name. 18 18 00:00:40,710 --> 00:00:42,650 So here, we're calling another function. 19 19 00:00:42,650 --> 00:00:44,275 Just like the print function. 20 20 00:00:44,275 --> 00:00:45,290 But in this case, 21 21 00:00:45,290 --> 00:00:48,865 this function here will print this prompt out. 22 22 00:00:48,865 --> 00:00:53,550 And then, it will wait for the user to type and press enter. 23 23 00:00:53,550 --> 00:00:56,450 line:15% Then, we're gonna print out the name. 24 24 00:00:56,450 --> 00:00:57,860 line:15% So, I've run this code here, 25 25 00:00:57,860 --> 00:01:00,570 line:15% and you can see that we get asked to enter our name. 26 26 00:01:00,570 --> 00:01:02,400 line:15% I'm gonna type here, Rolf. 27 27 00:01:02,400 --> 00:01:04,670 line:15% And then, Rolf comes back out. 28 28 00:01:04,670 --> 00:01:08,350 line:15% So, this is how you can ask the user for their name, 29 29 00:01:08,350 --> 00:01:10,260 or indeed, any other piece of data. 30 30 00:01:10,260 --> 00:01:12,323 And then, use it in your programmes. 31 31 00:01:13,370 --> 00:01:16,440 If you wanted to ask the user for a value 32 32 00:01:16,440 --> 00:01:18,620 that you want to do mathematics on, 33 33 00:01:18,620 --> 00:01:20,750 then there is something important to take into account 34 34 00:01:20,750 --> 00:01:22,390 when you're coding in Python. 35 35 00:01:22,390 --> 00:01:25,740 And that is that the input function always 36 36 00:01:25,740 --> 00:01:27,710 gives you back a string. 37 37 00:01:27,710 --> 00:01:30,580 So, this input will ask the user for a value, 38 38 00:01:30,580 --> 00:01:32,275 and it will give you a string. 39 39 00:01:32,275 --> 00:01:36,408 Now, remember that you can't do mathematics on strings 40 40 00:01:36,408 --> 00:01:39,360 in the same way that you can with numbers. 41 41 00:01:39,360 --> 00:01:41,210 So, if you wanted to calculate the amount 42 42 00:01:41,210 --> 00:01:43,440 of square metres that is the equivalent 43 43 00:01:43,440 --> 00:01:45,770 to the size of their house in square feet, 44 44 00:01:45,770 --> 00:01:49,030 you would do size input, divided by ten point eight. 45 45 00:01:49,030 --> 00:01:51,210 That's more or less the right number. 46 46 00:01:51,210 --> 00:01:53,530 And then, you can print square metres. 47 47 00:01:53,530 --> 00:01:56,410 But, remember that you can't do maths that well. 48 48 00:01:56,410 --> 00:01:57,620 So, if I save this, 49 49 00:01:57,620 --> 00:01:59,633 and then I go ahead and run it, 50 50 00:02:00,662 --> 00:02:05,060 line:15% and I ask for example my size is 500 square feet, 51 51 00:02:05,060 --> 00:02:06,380 line:15% you're gonna get an error. 52 52 00:02:06,380 --> 00:02:09,030 line:15% And you can see here that you've got a type error, 53 53 00:02:09,030 --> 00:02:09,863 line:15% and it says, 54 54 00:02:09,863 --> 00:02:12,790 line:15% unsupported operand types for the division 55 55 00:02:12,790 --> 00:02:14,800 line:15% string and float. 56 56 00:02:14,800 --> 00:02:16,490 So, what this is saying basically is that 57 57 00:02:16,490 --> 00:02:20,060 we've tried dividing a string by a float, 58 58 00:02:20,060 --> 00:02:21,800 and you can't do that. 59 59 00:02:21,800 --> 00:02:25,860 So, we need to convert this into a number 60 60 00:02:25,860 --> 00:02:27,570 instead of a string. 61 61 00:02:27,570 --> 00:02:29,162 So, what we've got to do is we have to 62 62 00:02:29,162 --> 00:02:32,920 first turn this size input into a number. 63 63 00:02:32,920 --> 00:02:34,240 So, what I'm gonna do is I'm gonna define 64 64 00:02:34,240 --> 00:02:35,880 a variable called square feet, 65 65 00:02:35,880 --> 00:02:39,170 and I'm gonna say "int" of size input. 66 66 00:02:39,170 --> 00:02:40,720 And what this is doing is it's 67 67 00:02:40,720 --> 00:02:43,230 doing something like what we had before. 68 68 00:02:43,230 --> 00:02:47,950 We are passing size input into another function, 69 69 00:02:47,950 --> 00:02:49,530 which is this int. 70 70 00:02:49,530 --> 00:02:51,860 And that is going to try to turn our string 71 71 00:02:51,860 --> 00:02:54,290 into an integer, a whole number. 72 72 00:02:54,290 --> 00:02:56,820 So that we can then do maths on it. 73 73 00:02:56,820 --> 00:02:59,060 Notice that here in our square metres line, 74 74 00:02:59,060 --> 00:03:00,520 we're still using size input, 75 75 00:03:00,520 --> 00:03:02,080 which is our string. 76 76 00:03:02,080 --> 00:03:04,270 If we wanna make sure that we use the number, 77 77 00:03:04,270 --> 00:03:07,030 we must use this square feet variable 78 78 00:03:07,030 --> 00:03:08,940 that we've defined on line two. 79 79 00:03:08,940 --> 00:03:11,853 Otherwise, that means we're still using the string. 80 80 00:03:12,970 --> 00:03:15,283 Let's save this and then run it. 81 81 00:03:16,230 --> 00:03:18,060 line:15% So here, we've got this app running, 82 82 00:03:18,060 --> 00:03:19,520 line:15% and I'm gonna type in 500. 83 83 00:03:19,520 --> 00:03:22,410 line:15% And now we get 46.3. 84 84 00:03:22,410 --> 00:03:24,440 So here's a small challenge for you. 85 85 00:03:24,440 --> 00:03:26,750 Try to print something a little bit nicer, 86 86 00:03:26,750 --> 00:03:28,770 rather than just this square metres. 87 87 00:03:28,770 --> 00:03:30,850 For example, you could print something like, 88 88 00:03:30,850 --> 00:03:33,300 this number of square feet is equal to this number 89 89 00:03:33,300 --> 00:03:34,313 of square metres. 90 90 00:03:35,760 --> 00:03:37,950 I'd recommend pausing the video and giving it a go. 91 91 00:03:37,950 --> 00:03:40,470 But, I'll try and do it right now as well. 92 92 00:03:40,470 --> 00:03:41,910 We're gonna use an "f" string. 93 93 00:03:41,910 --> 00:03:43,510 So I will type the f-key, 94 94 00:03:43,510 --> 00:03:45,300 and then the double quotation marks, 95 95 00:03:45,300 --> 00:03:46,133 and inside it, 96 96 00:03:46,133 --> 00:03:48,383 I'm gonna use my square feet variable, 97 97 00:03:49,370 --> 00:03:53,555 and type square feet, square feet is square metres, 98 98 00:03:53,555 --> 00:03:55,373 square metres. 99 99 00:03:56,960 --> 00:03:59,850 Notice that this here is the variable 100 100 00:03:59,850 --> 00:04:02,530 that we wanna put the value of inside our string. 101 101 00:04:02,530 --> 00:04:05,780 So, we still have to say what that variable means. 102 102 00:04:05,780 --> 00:04:10,780 So, for example, 500 square feet is 46 square metres. 103 103 00:04:12,490 --> 00:04:14,010 line:15% So, if we run this again, 104 104 00:04:14,010 --> 00:04:16,330 line:15% you'll see that as soon I type a 500, 105 105 00:04:16,330 --> 00:04:17,860 line:15% we get a nicer input. 106 106 00:04:17,860 --> 00:04:20,603 line:15% 500 square feet is 46 square metres. 107 107 00:04:21,710 --> 00:04:24,580 If you want to format a floating point number, 108 108 00:04:24,580 --> 00:04:27,970 so that you only get a certain number of digits at the end, 109 109 00:04:27,970 --> 00:04:30,590 you can do point two f, for example. 110 110 00:04:30,590 --> 00:04:32,840 So here, what we've got is a slightly more obscure 111 111 00:04:32,840 --> 00:04:33,770 piece of syntax. 112 112 00:04:33,770 --> 00:04:38,770 We've got square metres colon point two f. 113 113 00:04:38,947 --> 00:04:40,260 And what that does, 114 114 00:04:40,260 --> 00:04:44,380 is it will try to format this square metres 115 115 00:04:44,380 --> 00:04:46,580 with two decimal places only. 116 116 00:04:46,580 --> 00:04:48,900 This is what this piece of syntax means. 117 117 00:04:48,900 --> 00:04:49,770 line:15% So, I'm gonna save that, 118 118 00:04:49,770 --> 00:04:51,350 line:15% run it again, 119 119 00:04:51,350 --> 00:04:56,350 line:15% and now you see we get 46.30 square metres. 120 120 00:04:56,770 --> 00:04:59,550 If you want to learn more about this formatting syntax, 121 121 00:04:59,550 --> 00:05:02,030 I'm gonna leave a link in the resources section 122 122 00:05:02,030 --> 00:05:02,863 of this lecture, 123 123 00:05:02,863 --> 00:05:04,330 or on the description below, 124 124 00:05:04,330 --> 00:05:05,898 so that you can have a read of that. 125 125 00:05:05,898 --> 00:05:07,440 Well, that's everything for this video. 126 126 00:05:07,440 --> 00:05:09,480 We've learned how to get user input, 127 127 00:05:09,480 --> 00:05:11,330 and how to turn it into a number, 128 128 00:05:11,330 --> 00:05:12,986 in case we need to do maths on it. 129 129 00:05:12,986 --> 00:05:14,690 Thanks for joining me in this one, 130 130 00:05:14,690 --> 00:05:16,340 and I'll see you in the next one.