WEBVTT 1 00:00:01.080 --> 00:00:02.580 Hi, guys and welcome back. 2 00:00:02.580 --> 00:00:05.690 In this video, we're going to learn about lists, tuples, 3 00:00:05.690 --> 00:00:09.610 and sets. Three different collections in Python that 4 00:00:09.610 --> 00:00:13.470 allows us to store multiple values in a single variable. 5 00:00:13.470 --> 00:00:15.090 So that we can use them all at once 6 00:00:15.090 --> 00:00:17.383 or maybe extract some of them individually. 7 00:00:18.550 --> 00:00:19.970 Let's get started. 8 00:00:19.970 --> 00:00:22.370 We're going to define one of each just so you 9 00:00:22.370 --> 00:00:24.780 know how they are defined. 10 00:00:24.780 --> 00:00:29.493 So, l is going to be a list of three elements. 11 00:00:31.290 --> 00:00:34.620 And here I've created a variable called l for lists 12 00:00:34.620 --> 00:00:36.720 and I've made it equal to a list. 13 00:00:36.720 --> 00:00:40.340 The list is defined by using square brackets 14 00:00:40.340 --> 00:00:42.830 and inside the square brackets you can put different 15 00:00:42.830 --> 00:00:46.150 values as long as they are separated by a comma. 16 00:00:46.150 --> 00:00:49.630 So what I've got here is one string, then I've got a comma, 17 00:00:49.630 --> 00:00:51.990 then I've got another string, then I've got another comma, 18 00:00:51.990 --> 00:00:54.820 and then I've got another string. So three strings separated 19 00:00:54.820 --> 00:00:58.703 by commas inside square brackets. This defines a list. 20 00:00:59.620 --> 00:01:02.680 If you didn't have lists or tuples or sets, 21 00:01:02.680 --> 00:01:04.720 you would have to define three variables, 22 00:01:04.720 --> 00:01:06.010 one for each friend. 23 00:01:06.010 --> 00:01:07.780 And that would make it difficult to interact 24 00:01:07.780 --> 00:01:09.360 with all the values at once. 25 00:01:09.360 --> 00:01:10.640 You'll understand what I mean 26 00:01:10.640 --> 00:01:12.633 as we progress through the video. 27 00:01:14.120 --> 00:01:18.640 A tuple is very similar to a list but instead of using 28 00:01:18.640 --> 00:01:21.750 square brackets you use normal brackets. 29 00:01:21.750 --> 00:01:24.370 The key difference between lists and tuples is that 30 00:01:24.370 --> 00:01:28.470 you can't modify a tuple, whereas you can add and remove 31 00:01:28.470 --> 00:01:31.300 elements from a list, you can't add and remove 32 00:01:31.300 --> 00:01:32.480 elements from a tuple. 33 00:01:32.480 --> 00:01:35.040 That's the key difference between the two. 34 00:01:35.040 --> 00:01:39.390 Finally, a set is, again very similar, but you use curly 35 00:01:39.390 --> 00:01:42.703 braces instead of square or normal brackets. 36 00:01:45.490 --> 00:01:48.230 And the key difference between a set and the other two 37 00:01:48.230 --> 00:01:50.460 is that while you can add and remove elements from 38 00:01:50.460 --> 00:01:53.440 a set you can't have duplicate elements. 39 00:01:53.440 --> 00:01:57.070 So you couldn't have Bob twice in the set. 40 00:01:57.070 --> 00:02:01.290 Also, lists and tuples keep the order of the elements. 41 00:02:01.290 --> 00:02:04.220 So whenever you print out this list, it will always have 42 00:02:04.220 --> 00:02:07.120 Bob then Rolf and then Anne in that order, 43 00:02:07.120 --> 00:02:09.800 but sets don't necessarily keep the order, 44 00:02:09.800 --> 00:02:11.500 rather the order is not guaranteed. 45 00:02:11.500 --> 00:02:13.740 So the order could change at any moment. 46 00:02:13.740 --> 00:02:16.920 Sets are useful in a few scenarios that we will learn 47 00:02:16.920 --> 00:02:18.523 about in the coming videos. 48 00:02:19.520 --> 00:02:23.490 You can access individual elements of a list or a tuple 49 00:02:23.490 --> 00:02:25.840 by using subscript notation. 50 00:02:25.840 --> 00:02:27.653 So for example, you can print l. 51 00:02:30.050 --> 00:02:33.060 So what we've got here is our list variable 52 00:02:33.060 --> 00:02:35.487 and then we've got [0]. 53 00:02:37.050 --> 00:02:39.400 This notation here is called subscript notation 54 00:02:39.400 --> 00:02:41.860 and you can apply it to many things in Python 55 00:02:41.860 --> 00:02:43.970 but you can use it on lists and tuples 56 00:02:43.970 --> 00:02:48.823 and what it does is give you that element with index zero. 57 00:02:49.830 --> 00:02:52.890 Elements in programming usually start counting at zero, 58 00:02:52.890 --> 00:02:57.120 so the first element here, Bob has an index of zero. 59 00:02:57.120 --> 00:02:58.700 Then this one has an index of one, 60 00:02:58.700 --> 00:03:00.320 and this one has an index of two. 61 00:03:00.320 --> 00:03:05.120 So you could access Anne by doing l[2]. 62 00:03:05.120 --> 00:03:08.040 This also works for tuples so you can use your tuple 63 00:03:08.040 --> 00:03:11.210 variable there instead and that's totally find as well. 64 00:03:11.210 --> 00:03:14.340 However, it doesn't make sense to do that in sets 65 00:03:14.340 --> 00:03:16.240 because they don't have any order. 66 00:03:16.240 --> 00:03:18.780 So if you access the third element of a set, 67 00:03:18.780 --> 00:03:20.290 you don't know what you're going to get. 68 00:03:20.290 --> 00:03:22.510 That's why sets don't allow you 69 00:03:22.510 --> 00:03:24.313 to use subscript notation on them. 70 00:03:25.520 --> 00:03:28.900 You can modify individual items in a list by accessing 71 00:03:28.900 --> 00:03:31.870 the item itself using subscript notation 72 00:03:31.870 --> 00:03:34.140 and then you treating it like a variable. 73 00:03:34.140 --> 00:03:37.790 So for example, you can say l[0] equals Smith 74 00:03:37.790 --> 00:03:39.900 and then if you print your list and you run it, 75 00:03:39.900 --> 00:03:43.320 you will see that the first element is now Smith, 76 00:03:43.320 --> 00:03:45.470 second one's Rolf and the third one's Anne. 77 00:03:47.020 --> 00:03:51.150 However, if you're trying to modify a tuples element 78 00:03:51.150 --> 00:03:54.510 and you run this file, you will actually get an error 79 00:03:54.510 --> 00:03:58.060 because tuples cannot be modified after they're created 80 00:03:58.060 --> 00:04:01.643 so you can't use the equal sign on anything inside a tuple. 81 00:04:02.700 --> 00:04:04.630 Of course you can not do this on a set 82 00:04:04.630 --> 00:04:07.583 because a set does not allow for this subscript notation. 83 00:04:08.650 --> 00:04:12.900 You can add elements to a list by doing l.append 84 00:04:12.900 --> 00:04:16.480 and what append does is it will add an element 85 00:04:16.480 --> 00:04:17.930 to the end of the list. 86 00:04:17.930 --> 00:04:21.220 So if we append, for example, Smith to this list 87 00:04:21.220 --> 00:04:23.300 and then print it out you'll see that this list 88 00:04:23.300 --> 00:04:25.320 will now have four elements. 89 00:04:25.320 --> 00:04:27.413 That's Bob, Rolf, Anne, and Smith. 90 00:04:28.460 --> 00:04:31.910 But again because tuples to not allow modification, 91 00:04:31.910 --> 00:04:34.440 you can't change them, then if you do something like this 92 00:04:34.440 --> 00:04:36.220 you're also going to get an error and it's going to tell you 93 00:04:36.220 --> 00:04:40.030 that the tuple object has no attribute append. 94 00:04:40.030 --> 00:04:43.410 What that means is that we tried to access something 95 00:04:43.410 --> 00:04:47.257 called append inside, and that's what this full stop means 96 00:04:47.257 --> 00:04:51.170 so we're trying to access append inside of our tuple 97 00:04:51.170 --> 00:04:54.810 but our tuple doesn't have anything called append inside it. 98 00:04:54.810 --> 00:04:57.950 We're going to learn more about what I mean by inside 99 00:04:57.950 --> 00:05:00.460 in the next few videos. It is a little bit 100 00:05:00.460 --> 00:05:03.980 of a more complicated topic but rest assured you can't 101 00:05:03.980 --> 00:05:06.633 add things or remove things from a tuple. 102 00:05:08.160 --> 00:05:12.890 Talking about removal, you can remove things from a list. 103 00:05:12.890 --> 00:05:16.430 We're doing l.remove and then passing in the element 104 00:05:16.430 --> 00:05:17.300 that you want to remove. 105 00:05:17.300 --> 00:05:19.550 For example, if you wanted to remove Bob, 106 00:05:19.550 --> 00:05:21.420 then this would do that and then if you 107 00:05:21.420 --> 00:05:24.770 print(l) then you'll see that Bob has been removed 108 00:05:24.770 --> 00:05:27.203 and you are only left with Rolf and Anne. 109 00:05:28.830 --> 00:05:31.970 Going back to adding, you can add things to a set. 110 00:05:31.970 --> 00:05:35.880 So you can do s.add("Smith") then you can print your set 111 00:05:38.480 --> 00:05:39.500 and here you can see you that you get 112 00:05:39.500 --> 00:05:42.660 Anne, Bob, Smith, and Rolf. Notice that the order is 113 00:05:42.660 --> 00:05:45.930 not the same as when we created this, but all the elements 114 00:05:45.930 --> 00:05:49.860 are there. However, if you do the same thing twice, 115 00:05:49.860 --> 00:05:52.430 you'll see that Smith will only be here once. 116 00:05:52.430 --> 00:05:54.240 That's because, even though we told the set 117 00:05:54.240 --> 00:05:57.760 to add Smith twice there can be no duplicate elements 118 00:05:57.760 --> 00:06:01.043 inside a set, so this second Smith is actually ignored. 119 00:06:02.160 --> 00:06:05.850 This was a very brief primer or refresher regarding what 120 00:06:05.850 --> 00:06:08.140 lists, tuples and sets are. 121 00:06:08.140 --> 00:06:12.290 So just remember that lists are the most standard collection 122 00:06:12.290 --> 00:06:15.250 where you add and remove elements as well as modify them. 123 00:06:15.250 --> 00:06:18.370 In a tuple you have those elements and you can't modify them 124 00:06:18.370 --> 00:06:20.270 and you can't add or remove elements. 125 00:06:20.270 --> 00:06:23.480 And finally, a set, has no duplicate elements 126 00:06:23.480 --> 00:06:25.803 and it also has no order. 127 00:06:27.000 --> 00:06:28.300 That's everything for this video. 128 00:06:28.300 --> 00:06:29.400 Thank you for joining me. 129 00:06:29.400 --> 00:06:31.050 And I'll see you in the next one.