WEBVTT 1 00:00:00.234 --> 00:00:01.940 Hi guys, and welcome back! 2 00:00:01.940 --> 00:00:04.700 In this video, we'll learn about getting user input 3 00:00:04.700 --> 00:00:05.910 so that we can get some data 4 00:00:05.910 --> 00:00:08.783 from our users and use it in our programmes. 5 00:00:09.700 --> 00:00:12.200 Let's start off by asking the user for their name, 6 00:00:12.200 --> 00:00:13.510 so we can print it out. 7 00:00:13.510 --> 00:00:16.410 We will say name equals, and again, 8 00:00:16.410 --> 00:00:18.360 this is us defining a variable. 9 00:00:18.360 --> 00:00:20.390 Now, we have to tell the variable what its 10 00:00:20.390 --> 00:00:21.800 value is going to be. 11 00:00:21.800 --> 00:00:23.620 So what we're gonna do here is we're going to 12 00:00:23.620 --> 00:00:26.630 ask the user for their name. 13 00:00:26.630 --> 00:00:28.690 And the way we do that in Python is we type, 14 00:00:28.690 --> 00:00:30.820 input, then a pair of brackets, 15 00:00:30.820 --> 00:00:33.680 and inside the brackets we are gonna type a question 16 00:00:33.680 --> 00:00:36.200 that we'll ask the user or a prompt. 17 00:00:36.200 --> 00:00:40.710 So here, goes a string where we put enter your name. 18 00:00:40.710 --> 00:00:42.650 So here, we're calling another function. 19 00:00:42.650 --> 00:00:44.275 Just like the print function. 20 00:00:44.275 --> 00:00:45.290 But in this case, 21 00:00:45.290 --> 00:00:48.865 this function here will print this prompt out. 22 00:00:48.865 --> 00:00:53.550 And then, it will wait for the user to type and press enter. 23 00:00:53.550 --> 00:00:56.450 line:15% Then, we're gonna print out the name. 24 00:00:56.450 --> 00:00:57.860 line:15% So, I've run this code here, 25 00:00:57.860 --> 00:01:00.570 line:15% and you can see that we get asked to enter our name. 26 00:01:00.570 --> 00:01:02.400 line:15% I'm gonna type here, Rolf. 27 00:01:02.400 --> 00:01:04.670 line:15% And then, Rolf comes back out. 28 00:01:04.670 --> 00:01:08.350 line:15% So, this is how you can ask the user for their name, 29 00:01:08.350 --> 00:01:10.260 or indeed, any other piece of data. 30 00:01:10.260 --> 00:01:12.323 And then, use it in your programmes. 31 00:01:13.370 --> 00:01:16.440 If you wanted to ask the user for a value 32 00:01:16.440 --> 00:01:18.620 that you want to do mathematics on, 33 00:01:18.620 --> 00:01:20.750 then there is something important to take into account 34 00:01:20.750 --> 00:01:22.390 when you're coding in Python. 35 00:01:22.390 --> 00:01:25.740 And that is that the input function always 36 00:01:25.740 --> 00:01:27.710 gives you back a string. 37 00:01:27.710 --> 00:01:30.580 So, this input will ask the user for a value, 38 00:01:30.580 --> 00:01:32.275 and it will give you a string. 39 00:01:32.275 --> 00:01:36.408 Now, remember that you can't do mathematics on strings 40 00:01:36.408 --> 00:01:39.360 in the same way that you can with numbers. 41 00:01:39.360 --> 00:01:41.210 So, if you wanted to calculate the amount 42 00:01:41.210 --> 00:01:43.440 of square metres that is the equivalent 43 00:01:43.440 --> 00:01:45.770 to the size of their house in square feet, 44 00:01:45.770 --> 00:01:49.030 you would do size input, divided by ten point eight. 45 00:01:49.030 --> 00:01:51.210 That's more or less the right number. 46 00:01:51.210 --> 00:01:53.530 And then, you can print square metres. 47 00:01:53.530 --> 00:01:56.410 But, remember that you can't do maths that well. 48 00:01:56.410 --> 00:01:57.620 So, if I save this, 49 00:01:57.620 --> 00:01:59.633 and then I go ahead and run it, 50 00:02:00.662 --> 00:02:05.060 line:15% and I ask for example my size is 500 square feet, 51 00:02:05.060 --> 00:02:06.380 line:15% you're gonna get an error. 52 00:02:06.380 --> 00:02:09.030 line:15% And you can see here that you've got a type error, 53 00:02:09.030 --> 00:02:09.863 line:15% and it says, 54 00:02:09.863 --> 00:02:12.790 line:15% unsupported operand types for the division 55 00:02:12.790 --> 00:02:14.800 line:15% string and float. 56 00:02:14.800 --> 00:02:16.490 So, what this is saying basically is that 57 00:02:16.490 --> 00:02:20.060 we've tried dividing a string by a float, 58 00:02:20.060 --> 00:02:21.800 and you can't do that. 59 00:02:21.800 --> 00:02:25.860 So, we need to convert this into a number 60 00:02:25.860 --> 00:02:27.570 instead of a string. 61 00:02:27.570 --> 00:02:29.162 So, what we've got to do is we have to 62 00:02:29.162 --> 00:02:32.920 first turn this size input into a number. 63 00:02:32.920 --> 00:02:34.240 So, what I'm gonna do is I'm gonna define 64 00:02:34.240 --> 00:02:35.880 a variable called square feet, 65 00:02:35.880 --> 00:02:39.170 and I'm gonna say "int" of size input. 66 00:02:39.170 --> 00:02:40.720 And what this is doing is it's 67 00:02:40.720 --> 00:02:43.230 doing something like what we had before. 68 00:02:43.230 --> 00:02:47.950 We are passing size input into another function, 69 00:02:47.950 --> 00:02:49.530 which is this int. 70 00:02:49.530 --> 00:02:51.860 And that is going to try to turn our string 71 00:02:51.860 --> 00:02:54.290 into an integer, a whole number. 72 00:02:54.290 --> 00:02:56.820 So that we can then do maths on it. 73 00:02:56.820 --> 00:02:59.060 Notice that here in our square metres line, 74 00:02:59.060 --> 00:03:00.520 we're still using size input, 75 00:03:00.520 --> 00:03:02.080 which is our string. 76 00:03:02.080 --> 00:03:04.270 If we wanna make sure that we use the number, 77 00:03:04.270 --> 00:03:07.030 we must use this square feet variable 78 00:03:07.030 --> 00:03:08.940 that we've defined on line two. 79 00:03:08.940 --> 00:03:11.853 Otherwise, that means we're still using the string. 80 00:03:12.970 --> 00:03:15.283 Let's save this and then run it. 81 00:03:16.230 --> 00:03:18.060 line:15% So here, we've got this app running, 82 00:03:18.060 --> 00:03:19.520 line:15% and I'm gonna type in 500. 83 00:03:19.520 --> 00:03:22.410 line:15% And now we get 46.3. 84 00:03:22.410 --> 00:03:24.440 So here's a small challenge for you. 85 00:03:24.440 --> 00:03:26.750 Try to print something a little bit nicer, 86 00:03:26.750 --> 00:03:28.770 rather than just this square metres. 87 00:03:28.770 --> 00:03:30.850 For example, you could print something like, 88 00:03:30.850 --> 00:03:33.300 this number of square feet is equal to this number 89 00:03:33.300 --> 00:03:34.313 of square metres. 90 00:03:35.760 --> 00:03:37.950 I'd recommend pausing the video and giving it a go. 91 00:03:37.950 --> 00:03:40.470 But, I'll try and do it right now as well. 92 00:03:40.470 --> 00:03:41.910 We're gonna use an "f" string. 93 00:03:41.910 --> 00:03:43.510 So I will type the f-key, 94 00:03:43.510 --> 00:03:45.300 and then the double quotation marks, 95 00:03:45.300 --> 00:03:46.133 and inside it, 96 00:03:46.133 --> 00:03:48.383 I'm gonna use my square feet variable, 97 00:03:49.370 --> 00:03:53.555 and type square feet, square feet is square metres, 98 00:03:53.555 --> 00:03:55.373 square metres. 99 00:03:56.960 --> 00:03:59.850 Notice that this here is the variable 100 00:03:59.850 --> 00:04:02.530 that we wanna put the value of inside our string. 101 00:04:02.530 --> 00:04:05.780 So, we still have to say what that variable means. 102 00:04:05.780 --> 00:04:10.780 So, for example, 500 square feet is 46 square metres. 103 00:04:12.490 --> 00:04:14.010 line:15% So, if we run this again, 104 00:04:14.010 --> 00:04:16.330 line:15% you'll see that as soon I type a 500, 105 00:04:16.330 --> 00:04:17.860 line:15% we get a nicer input. 106 00:04:17.860 --> 00:04:20.603 line:15% 500 square feet is 46 square metres. 107 00:04:21.710 --> 00:04:24.580 If you want to format a floating point number, 108 00:04:24.580 --> 00:04:27.970 so that you only get a certain number of digits at the end, 109 00:04:27.970 --> 00:04:30.590 you can do point two f, for example. 110 00:04:30.590 --> 00:04:32.840 So here, what we've got is a slightly more obscure 111 00:04:32.840 --> 00:04:33.770 piece of syntax. 112 00:04:33.770 --> 00:04:38.770 We've got square metres colon point two f. 113 00:04:38.947 --> 00:04:40.260 And what that does, 114 00:04:40.260 --> 00:04:44.380 is it will try to format this square metres 115 00:04:44.380 --> 00:04:46.580 with two decimal places only. 116 00:04:46.580 --> 00:04:48.900 This is what this piece of syntax means. 117 00:04:48.900 --> 00:04:49.770 line:15% So, I'm gonna save that, 118 00:04:49.770 --> 00:04:51.350 line:15% run it again, 119 00:04:51.350 --> 00:04:56.350 line:15% and now you see we get 46.30 square metres. 120 00:04:56.770 --> 00:04:59.550 If you want to learn more about this formatting syntax, 121 00:04:59.550 --> 00:05:02.030 I'm gonna leave a link in the resources section 122 00:05:02.030 --> 00:05:02.863 of this lecture, 123 00:05:02.863 --> 00:05:04.330 or on the description below, 124 00:05:04.330 --> 00:05:05.898 so that you can have a read of that. 125 00:05:05.898 --> 00:05:07.440 Well, that's everything for this video. 126 00:05:07.440 --> 00:05:09.480 We've learned how to get user input, 127 00:05:09.480 --> 00:05:11.330 and how to turn it into a number, 128 00:05:11.330 --> 00:05:12.986 in case we need to do maths on it. 129 00:05:12.986 --> 00:05:14.690 Thanks for joining me in this one, 130 00:05:14.690 --> 00:05:16.340 and I'll see you in the next one.