WEBVTT 1 00:00:00.340 --> 00:00:01.900 Hi guys, and welcome back. 2 00:00:01.900 --> 00:00:05.180 In this video, we're going to talk about tuples. 3 00:00:05.180 --> 00:00:07.220 Tuples are very similar to lists in that 4 00:00:07.220 --> 00:00:10.450 they are used to store multiple pieces of information. 5 00:00:10.450 --> 00:00:13.040 But there is a small, subtle difference 6 00:00:13.040 --> 00:00:15.340 between tuples and lists, let's jump right in. 7 00:00:16.820 --> 00:00:18.780 A tuple can be defined like this, 8 00:00:18.780 --> 00:00:21.000 let's imagine you've got a short tuple 9 00:00:21.000 --> 00:00:22.980 that contains two of your friend names, 10 00:00:22.980 --> 00:00:26.590 you can just say Rolf comma Bob. 11 00:00:26.590 --> 00:00:29.000 Notice that there are no square brackets now 12 00:00:29.000 --> 00:00:32.530 around these two strings, but there is a comma 13 00:00:32.530 --> 00:00:34.970 in between them so you've got one string 14 00:00:34.970 --> 00:00:36.440 and then another string. 15 00:00:36.440 --> 00:00:38.500 This is a tuple. 16 00:00:38.500 --> 00:00:42.300 You can think of it as almost the same thing as a list, 17 00:00:42.300 --> 00:00:45.120 but I'll show you the difference in just a moment. 18 00:00:45.120 --> 00:00:49.580 It's often good form to put brackets around this. 19 00:00:49.580 --> 00:00:51.913 So this is a bit clearer. 20 00:00:52.750 --> 00:00:57.750 If you put brackets around the two strings like that, 21 00:00:58.210 --> 00:01:00.610 this is a little bit clearer that it's a tuple, 22 00:01:00.610 --> 00:01:02.870 and almost all of the time you are going to see 23 00:01:02.870 --> 00:01:06.150 tuples defined with the brackets around them. 24 00:01:06.150 --> 00:01:07.480 But remember that the brackets 25 00:01:07.480 --> 00:01:10.300 are not required in many cases. 26 00:01:10.300 --> 00:01:12.800 Although there are some cases where they will be, 27 00:01:12.800 --> 00:01:15.280 and that is when Python cannot be sure 28 00:01:15.280 --> 00:01:18.920 if the comma is used to separate two things 29 00:01:18.920 --> 00:01:21.840 inside a tuple or something else. 30 00:01:21.840 --> 00:01:25.210 For example, here's an occasion 31 00:01:25.210 --> 00:01:26.850 where you will need to use the brackets, 32 00:01:26.850 --> 00:01:30.490 which is when you want to put a tuple inside a list. 33 00:01:30.490 --> 00:01:34.560 If you have a list, and you wanna put a tuple inside it, 34 00:01:34.560 --> 00:01:35.803 and you do it like this, 35 00:01:36.780 --> 00:01:39.010 you have not put a tuple inside the list. 36 00:01:39.010 --> 00:01:41.410 What you've done is you've created a list of two elements 37 00:01:41.410 --> 00:01:43.310 as we saw in the last video. 38 00:01:43.310 --> 00:01:46.060 If you wanna create a list with a tuple inside it, 39 00:01:46.060 --> 00:01:48.830 you will need the brackets so that Python knows 40 00:01:48.830 --> 00:01:51.670 that you intend this to evaluate first, 41 00:01:51.670 --> 00:01:55.080 which creates a tuple, and then the list to evaluate later. 42 00:01:55.080 --> 00:01:56.820 That's what brackets are normally used for 43 00:01:56.820 --> 00:02:00.783 in mathematics as well, to signal order of evaluation. 44 00:02:02.270 --> 00:02:04.050 So, most of the time you're going to see 45 00:02:04.050 --> 00:02:06.280 your tuples defined with brackets around them, 46 00:02:06.280 --> 00:02:07.920 and I would encourage you to get accustomed 47 00:02:07.920 --> 00:02:10.080 to that notation as well. 48 00:02:10.080 --> 00:02:12.150 Something very important is that while 49 00:02:12.150 --> 00:02:14.320 you can write your tuples like this, 50 00:02:14.320 --> 00:02:17.820 this thing is most definitely not a tuple 51 00:02:17.820 --> 00:02:19.570 if you just write Rolf. 52 00:02:19.570 --> 00:02:23.070 If you write Rolf on its own, that's just a string, right? 53 00:02:23.070 --> 00:02:25.920 But if you add Rolf and then a comma, 54 00:02:25.920 --> 00:02:28.070 Python knows that you want a tuple there, 55 00:02:28.070 --> 00:02:30.400 and this, adding a comma at the end, 56 00:02:30.400 --> 00:02:31.890 is something that a lot of my students 57 00:02:31.890 --> 00:02:34.010 make as a mistake when they're starting out, 58 00:02:34.010 --> 00:02:36.370 they just put a comma at the end because you know, 59 00:02:36.370 --> 00:02:38.550 maybe they come from a different programming language, 60 00:02:38.550 --> 00:02:41.850 or maybe it's a title or a small mistake, 61 00:02:41.850 --> 00:02:43.210 and this can cause some trouble, 62 00:02:43.210 --> 00:02:46.190 so make sure to not put commas at the end of your statements 63 00:02:46.190 --> 00:02:49.700 in Python, because that turns strings, or anything else, 64 00:02:49.700 --> 00:02:51.950 into tuples, and that can be a bit confusing. 65 00:02:52.820 --> 00:02:55.290 So I've got this tuple here with my friend names, 66 00:02:55.290 --> 00:02:57.090 Rolf, Bob, and Anne, and let's say 67 00:02:57.090 --> 00:02:59.520 I wanna add something to this tuple. 68 00:02:59.520 --> 00:03:04.393 Like we learned with lists, friends.append, and then Jen. 69 00:03:05.400 --> 00:03:09.773 So if we run this now, you'll see that we'll get an error, 70 00:03:10.770 --> 00:03:14.840 and it says, attribute error, this is the name of the error, 71 00:03:14.840 --> 00:03:17.880 tuple object has no attribute append. 72 00:03:17.880 --> 00:03:20.830 And here it tells you the line in which the error occurred, 73 00:03:20.830 --> 00:03:23.343 which is line two of our code. 74 00:03:24.680 --> 00:03:29.680 What this means is that you can't do dot append on a tuple. 75 00:03:31.110 --> 00:03:33.860 Okay, so how do you add to a tuple 76 00:03:33.860 --> 00:03:35.593 if you can't append to it? 77 00:03:36.700 --> 00:03:40.253 Well, that's the thing, you cannot add to a tuple. 78 00:03:41.160 --> 00:03:43.780 Here we've got a tuple of three elements, 79 00:03:43.780 --> 00:03:47.350 and you cannot insert an extra element on this tuple. 80 00:03:47.350 --> 00:03:50.260 All you can do is say friends equal 81 00:03:50.260 --> 00:03:53.720 friends plus Jen, like that. 82 00:03:53.720 --> 00:03:56.730 So you can add two tuples together, 83 00:03:56.730 --> 00:04:00.693 in this case, the friends tuple and the Jen tuple 84 00:04:00.693 --> 00:04:03.190 with a single element, and those two, 85 00:04:03.190 --> 00:04:04.720 and say that friends is now equal 86 00:04:04.720 --> 00:04:06.800 to the result of adding them. 87 00:04:06.800 --> 00:04:08.650 Remember when you do an equal sign, 88 00:04:08.650 --> 00:04:11.350 the right side evaluates first, 89 00:04:11.350 --> 00:04:15.117 so this thing here uses the current value of friends 90 00:04:15.117 --> 00:04:18.460 and this new tuple, and then you give it the name friends, 91 00:04:18.460 --> 00:04:20.950 so you can reassign while using 92 00:04:20.950 --> 00:04:22.350 a variable in the assignment, 93 00:04:22.350 --> 00:04:24.770 that's totally fine, it just uses the last value 94 00:04:24.770 --> 00:04:27.200 of the variable if it existed. 95 00:04:27.200 --> 00:04:29.890 You can do this, if you want, 96 00:04:29.890 --> 00:04:33.540 and that will result in a tuple of four elements. 97 00:04:33.540 --> 00:04:36.040 But what's important, and an important distinction, 98 00:04:36.040 --> 00:04:38.580 is that the tuple itself did not change, 99 00:04:38.580 --> 00:04:42.580 you created a new one, which contains now four elements. 100 00:04:42.580 --> 00:04:45.960 And while that's relatively unimportant right now 101 00:04:45.960 --> 00:04:48.830 it will become important as you learn more Python, 102 00:04:48.830 --> 00:04:52.320 so that is the key difference between lists and tuples, 103 00:04:52.320 --> 00:04:57.010 lists, you can add and remove elements, tuples, you cannot. 104 00:04:57.010 --> 00:04:58.680 So that's the key difference. 105 00:04:58.680 --> 00:05:03.460 Tuples are useful for when you wanna keep them unchanged. 106 00:05:03.460 --> 00:05:07.470 Most of the time, I'd recommend using tuples over lists. 107 00:05:07.470 --> 00:05:10.220 And only use lists when you specifically want 108 00:05:10.220 --> 00:05:13.410 to allow modification or changes. 109 00:05:13.410 --> 00:05:15.880 Again, at the moment this may not make much sense, 110 00:05:15.880 --> 00:05:18.860 but you will find more meaning in that as you learn more. 111 00:05:18.860 --> 00:05:20.670 Trust me on that one. 112 00:05:20.670 --> 00:05:21.930 That's everything for this video though, 113 00:05:21.930 --> 00:05:23.090 we've learned about tuples, 114 00:05:23.090 --> 00:05:25.053 I'll see you on the next one.