WEBVTT 0 00:00.080 --> 00:07.310 Yesterday, you saw that we could use the len() function to get the number of characters in a string. 1 00:07.310 --> 00:16.430 So for example, when I write len("hello"), and I print this out, we end up with 5, there is 5 characters 2 00:16.430 --> 00:17.060 in the string 3 00:17.060 --> 00:17.750 "hello". 4 00:17.990 --> 00:19.850 Now here's a question. 5 00:19.850 --> 00:28.100 What happens if instead of counting the number of characters in a string, what if I put in a number 6 00:28.100 --> 00:32.610 instead and I wanted to know how many digits are in this number? 7 00:33.180 --> 00:38.010 Now, if I go ahead and run this code, you'll see that it actually crashes. 8 00:38.010 --> 00:45.510 I get a whole bunch of red text, and it tells me that there is a TypeError and something about the 9 00:45.510 --> 00:47.010 type 'int'. 10 00:47.250 --> 00:49.440 So what is all of this about? 11 00:49.530 --> 00:54.540 Well, in order to understand it, we first have to learn about Data Types. 12 00:54.990 --> 00:59.820 Now, on day one we already explored this data type called strings. 13 00:59.850 --> 01:05.160 Now, you're probably not going to be surprised to learn that there's a whole lot more other data types 14 01:05.160 --> 01:05.970 out there. 15 01:05.970 --> 01:12.630 And today we're going to explore some of the most important and some of the most basic data types, 16 01:12.630 --> 01:15.960 such as Strings, Integers, Floats, and Booleans. 17 01:15.960 --> 01:18.810 And we'll explore each of these in detail. 18 01:18.970 --> 01:21.730 So let's take a look at some of the data types. 19 01:21.730 --> 01:24.580 So we already learned about strings, right? 20 01:24.580 --> 01:29.140 And we know that this is just a string of characters. 21 01:29.140 --> 01:34.450 So the word "hello" is comprised of these five characters strung together. 22 01:34.450 --> 01:39.940 And we always know that strings, when we create them, we have to create them with these double quotes 23 01:39.940 --> 01:40.570 around. 24 01:40.570 --> 01:46.940 Now, because this is a string of characters we can actually pull out each character individually. 25 01:46.940 --> 01:53.420 So we could, for example, instead of just writing "hello", we can add some square brackets. 26 01:53.420 --> 01:56.750 So take a look on your keyboard and see where those are. 27 01:56.750 --> 02:04.370 And inside the square brackets we can put the index or the position of the character that we want. 28 02:04.370 --> 02:09.720 So for example, if I wanted to have the first character out of this word, "Hello", 29 02:09.750 --> 02:11.940 I would put 0 right here. 30 02:11.940 --> 02:19.800 And if I go ahead and print what this actually will give me, you'll see that you get capital H, because 31 02:19.800 --> 02:24.030 that is the first character of this string. 32 02:24.030 --> 02:30.840 And it's really important to remember that programmers always start counting from zero because we work 33 02:30.840 --> 02:32.640 with binary zeros and ones. 34 02:32.640 --> 02:39.990 So whenever you want to get hold of the first character or the first of anything, it always is at 0. 35 02:40.260 --> 02:48.000 So this method of pulling out a particular element from a string is called subscripting, and the number 36 02:48.000 --> 02:51.750 in between the square brackets determines which character you're going to pull out. 37 02:51.750 --> 02:57.330 And it just goes up from 0 to 1 to 2, and so on and so forth. 38 02:57.330 --> 03:04.030 So whenever you get a result that's just off by one, then remember to check whether if you've started 39 03:04.030 --> 03:07.750 counting from zero or if you started counting from one. 40 03:08.170 --> 03:12.820 Now you can of course extend this and get hold of the last character. 41 03:12.820 --> 03:18.070 So pause the video and see if you can change the code so that O gets printed out here. 42 03:19.300 --> 03:19.780 All right. 43 03:19.780 --> 03:24.890 So this is as simple as simply counting from zero, one two, three, four. 44 03:24.890 --> 03:31.100 So if we change this to 4 and we run our code, then you'll see that O gets printed instead of the 45 03:31.100 --> 03:31.670 H. 46 03:31.850 --> 03:38.090 Now there's also a secret trick that not many people know, even seasoned Python developers, 47 03:38.090 --> 03:41.840 and it's the fact that you can actually use negative indices. 48 03:41.840 --> 03:49.310 So instead of specifying the position as a positive number, you can also use a negative number, and 49 03:49.310 --> 03:56.240 -1, means get hold of the last character in the string so we can go ahead and run this, and you 50 03:56.240 --> 04:02.030 can see it's also O, and we can start counting backwards as well, starting from the end going to 51 04:02.030 --> 04:02.810 the beginning. 52 04:02.810 --> 04:04.400 So that's just a quick tip. 53 04:04.400 --> 04:11.330 So by using these square brackets and putting a number inside, we're able to dissect our string and 54 04:11.330 --> 04:17.220 pull out individual characters as and when we need it, and this will come in really handy in a lot 55 04:17.220 --> 04:19.470 of the programs that you'll write in the future. 56 04:19.860 --> 04:26.040 Now, it's important to remember, though, that just because I can write a number like, "1, 2, 57 04:26.040 --> 04:33.750 3," as long as it's capped inside these double quotes, then this is not treated as a number by 58 04:33.750 --> 04:34.380 the computer. 59 04:34.380 --> 04:37.260 It's treated just as any other piece of text. 60 04:37.360 --> 04:44.140 You can't, for example, say, what is "123" + "345"? 61 04:44.140 --> 04:48.850 If I try to print this, what do you think will happen? 62 04:48.850 --> 04:54.130 Do you think it will give me 123+345, in the traditional sense, like 63 04:54.130 --> 04:55.300 calculating it? 64 04:55.300 --> 04:57.490 Or do you think it'll do something else? 65 04:57.760 --> 04:59.350 All right, let's hit Run. 66 04:59.350 --> 05:02.980 And we get 123345. 67 05:02.980 --> 05:09.400 So it's basically just concatenated these two strings together, just as we have done with other strings 68 05:09.400 --> 05:11.830 like Hello and World. 69 05:11.830 --> 05:12.310 Right? 70 05:12.820 --> 05:17.710 Because it sees the data type of these two pieces of data as strings, 71 05:17.710 --> 05:25.270 when we use the plus sign, it will actually just concatenate these two things instead of doing a mathematical 72 05:25.270 --> 05:26.350 operation. 73 05:26.350 --> 05:33.170 Now, if we wanted to do that, then we actually have to declare our number as a number data type. 74 05:33.170 --> 05:36.830 So one of the most common that you'll see is called an integer. 75 05:36.830 --> 05:40.400 So this is programming lingo for just whole numbers. 76 05:40.400 --> 05:43.400 Numbers without any decimal places. 77 05:43.400 --> 05:50.240 And in order to create an integer or declare an integer data type, all you have to do is just write 78 05:50.240 --> 05:52.650 the number without anything else. 79 05:53.040 --> 05:59.100 So now if I just write the numbers 123 + 345, and then I go ahead 80 05:59.100 --> 06:03.600 and print this, then you'll see that we actually get 468. 81 06:03.600 --> 06:09.570 So it's actually being calculated because I've got actual numbers instead of strings. 82 06:10.140 --> 06:15.330 Just as we have some useful things that we can do with strings, there's some really handy things that 83 06:15.330 --> 06:16.840 you can do with integers. 84 06:17.140 --> 06:24.940 Commonly, when we write large numbers, at least in the UK or in the US, we like to put commas in 85 06:24.940 --> 06:26.170 between the thousands. 86 06:26.170 --> 06:32.830 So when we think of large numbers with these commas in between to split it into an easier to understand 87 06:32.830 --> 06:33.550 number, 88 06:33.640 --> 06:40.900 in Python we can replace those commas simply with underscores, and it will be interpreted by the computer 89 06:40.900 --> 06:43.390 as if you had written this. 90 06:43.390 --> 06:46.960 So the computer actually removes those underscores and ignores it. 91 06:47.080 --> 06:52.150 The benefit is just for us humans to be able to visualize it more easily. 92 06:52.540 --> 06:58.240 So I mentioned that all whole numbers, no matter if they're positive or negative, are called integers 93 06:58.240 --> 06:59.380 in programming. 94 06:59.380 --> 07:02.800 So what do you call it when you actually have decimal places? 95 07:02.800 --> 07:04.750 Well, they're called a float. 96 07:04.750 --> 07:08.360 And this is short for a floating point number. 97 07:08.360 --> 07:15.560 So for example, if you had the numbers of pi, you have 3.14159. 98 07:15.680 --> 07:21.140 And this because it has a decimal place is now a float data type. 99 07:21.380 --> 07:27.860 So if you think of the decimal point as being able to float around the number because it could occur 100 07:27.860 --> 07:31.980 at any point, then you've got yourself a floating point number. 101 07:32.910 --> 07:37.110 Now the final data type is something called a Boolean. 102 07:37.770 --> 07:39.300 And this is very simple. 103 07:39.300 --> 07:43.950 It only has two possible values True or False. 104 07:43.980 --> 07:51.840 Now note how these values always begin with a capital T or a capital F, and they don't have any quotation 105 07:51.840 --> 07:53.280 marks around them or anything. 106 07:53.280 --> 07:59.760 So this is actually a data type which is going to be used a lot in your programs to test if something 107 07:59.760 --> 08:04.350 is true or if something is false, and for your program to respond accordingly. 108 08:04.350 --> 08:07.530 So we're going to be using this a lot more in the future. 109 08:07.530 --> 08:13.470 Now that you've seen a lot of the basic data types Strings, Integers, Floats, and Boolean, I want 110 08:13.470 --> 08:18.600 you to head over to the next lesson where I've got a quiz for you to see if you've made this knowledge 111 08:18.600 --> 08:19.200 your own. 112 08:19.200 --> 08:21.630 So head over to the quiz and give it a go.