WEBVTT 00:00.610 --> 00:03.070 Hello, my name is Stefan from Oxford Academy. 00:03.070 --> 00:06.160 And in this section you will learn about lists. 00:06.190 --> 00:11.030 What lists are and how to start working with the elements in a list. 00:11.050 --> 00:18.190 So let's allow you to store sets of information in one place, whether you have just a few items or 00:18.190 --> 00:19.600 millions of items. 00:19.600 --> 00:29.860 So lists are one of the python's most powerful features, readily accessible to new programmers, and 00:29.860 --> 00:33.700 they tie together many important concepts in programming. 00:33.700 --> 00:36.520 So what is a list? 00:36.700 --> 00:38.560 A list is a collection of items. 00:38.560 --> 00:39.880 In a particular order. 00:39.910 --> 00:46.390 You can make a list that includes the letter alphabets. 00:47.260 --> 00:48.600 Digits here. 00:48.730 --> 00:49.780 Letters. 00:50.690 --> 00:53.000 A, B or. 00:54.410 --> 00:57.770 A the C here ads here. 00:57.800 --> 01:01.840 You can create a list of numbers here. 01:01.850 --> 01:03.920 One two. 01:05.760 --> 01:08.100 Three, four. 01:08.840 --> 01:09.590 Five. 01:09.800 --> 01:11.300 You can also create. 01:14.350 --> 01:16.810 List of characters here. 01:19.690 --> 01:28.270 Which you will learn all of this in this section so you can put anything you want into list and the 01:28.270 --> 01:32.130 items in your list don't have to be related in a particular way, right? 01:32.140 --> 01:42.010 So because a list is usually contains more than one element, it's a good idea to make the name of your 01:42.010 --> 01:43.330 list plural. 01:43.330 --> 01:44.740 Such as? 01:45.250 --> 01:48.310 Uh, for example, instead of writing. 01:48.340 --> 01:49.120 Oh, sorry. 01:49.820 --> 01:54.530 So instead of writing your list variable name letter. 01:58.550 --> 02:06.320 You can write letters because it's a more good practice here. 02:06.320 --> 02:08.180 So in Python. 02:08.390 --> 02:10.100 Square braces. 02:10.100 --> 02:12.410 This square braces. 02:15.850 --> 02:23.080 Indicator list and individual elements in the list are separated by commas. 02:25.620 --> 02:28.640 Separated by commas. 02:28.680 --> 02:30.930 So let's actually create a. 02:31.970 --> 02:35.880 Example, a list that contains a few kinds of courses. 02:35.920 --> 02:36.500 Right? 02:36.500 --> 02:37.580 So. 02:38.840 --> 02:42.050 So course topics here. 02:42.080 --> 02:44.330 It's going to be here. 02:44.330 --> 02:47.450 We have braces, brackets. 02:47.450 --> 02:50.450 So now we're going to car. 02:50.480 --> 02:55.670 As you can see, we are getting an error because we we need to enter a strings car. 02:56.030 --> 02:57.200 So we use single quotes. 02:59.410 --> 03:00.190 Car. 03:00.520 --> 03:05.080 And here we will also add Android Kotlin. 03:05.410 --> 03:08.260 We will also add Java. 03:09.830 --> 03:10.670 Python. 03:14.040 --> 03:15.900 Digital forensics. 03:16.720 --> 03:20.230 Actually, let's decrease the font size a little bit maybe. 03:20.230 --> 03:20.740 Yeah. 03:20.770 --> 03:22.690 And digital fonts is okay for now. 03:22.720 --> 03:28.000 So after that we will print the course topics list. 03:28.390 --> 03:32.470 And as you can see here, this is the output. 03:32.650 --> 03:40.990 So if you ask a python, print the list that's Python retains its representation of a list, including 03:40.990 --> 03:42.910 the square braces here. 03:42.940 --> 03:48.670 So because this is the output you want to use, you want users to see. 03:48.700 --> 03:52.960 Let's learn how to access the individual items. 03:53.380 --> 04:01.660 For example, Car, Android, Kotlin, Java, Python and digital forensics. 04:01.900 --> 04:03.130 Let's try this now. 04:03.130 --> 04:12.400 So lists are ordered collections so you can access any element in a list by telling Python the position 04:12.400 --> 04:15.130 or index of the item desired. 04:15.160 --> 04:23.060 So to access an element in a list, write the name of the list followed by the end index of the item. 04:23.060 --> 04:25.520 So now there's an interesting thing I want to. 04:26.540 --> 04:26.890 Sorry. 04:27.350 --> 04:28.610 Firstly, it's actually get. 04:29.520 --> 04:36.110 And so in order to access this list, we will write, print or actually instead of print, we can also 04:36.110 --> 04:36.500 write. 04:36.530 --> 04:40.460 Yeah, we will write print inside this list. 04:40.460 --> 04:42.920 We will get course topics here. 04:43.580 --> 04:44.630 Course. 04:50.020 --> 04:50.860 Topics. 04:52.550 --> 04:54.350 And here we will use. 04:55.710 --> 04:56.420 Braces. 04:56.460 --> 04:58.260 Brackets like this. 04:58.380 --> 05:01.440 Let's actually use this different color so I can show you. 05:02.220 --> 05:02.620 Here. 05:04.220 --> 05:07.240 This is the braces. 05:07.250 --> 05:11.840 So here we will add the nth element. 05:11.840 --> 05:12.680 So. 05:14.080 --> 05:14.650 And. 05:16.310 --> 05:17.030 Element. 05:21.010 --> 05:21.870 From list. 05:28.450 --> 05:29.860 So in this case. 05:30.500 --> 05:34.550 For example, if we want to access the cars, the car is going to be zero. 05:34.910 --> 05:40.030 Android Kotlin is going to be remember, let's let's actually use different color. 05:40.130 --> 05:41.060 So. 05:41.970 --> 05:43.950 The car is going to be. 05:46.810 --> 05:47.680 Zero. 05:47.710 --> 05:52.110 Android Kotlin is going to be one. 05:52.120 --> 05:55.180 Java is going to be two. 05:55.450 --> 05:58.720 Python is going to be third element in the list. 06:00.490 --> 06:04.500 Digital forensics is going to be fourth element in the list. 06:04.510 --> 06:07.840 So if you want to access the cars, we will write zero. 06:07.840 --> 06:12.130 If you want to access the Android Kotlin, we will write one here. 06:12.340 --> 06:16.240 But if we want to access Java, we will write two. 06:16.270 --> 06:23.770 If we want to access Python, as you know, we will write three because the python is the third element 06:23.770 --> 06:24.490 of the list. 06:24.490 --> 06:28.990 So list starts from the zero one, 234. 06:29.320 --> 06:34.360 So if we want to access the digital forensics, we will write the fourth. 06:35.360 --> 06:36.080 So. 06:39.150 --> 06:43.500 So here we will write course, print course topics. 06:44.960 --> 06:45.350 Zero. 06:45.350 --> 06:46.940 And as you can see, it's a car. 06:48.120 --> 06:48.570 Android. 06:48.570 --> 06:49.320 Kotlin. 06:50.610 --> 06:51.210 Java. 06:52.380 --> 06:53.070 Python. 06:54.930 --> 07:01.230 Now python and let's five ops and let's actually try Python now. 07:01.810 --> 07:02.290 So. 07:03.290 --> 07:05.390 I feel Bradford is going to be digital forensics. 07:05.390 --> 07:09.210 As we know, as I showed you earlier in this lecture. 07:09.230 --> 07:12.870 One, two, three, four, five. 07:12.890 --> 07:13.330 Right. 07:13.340 --> 07:16.030 Fifth element of the list in this case. 07:16.040 --> 07:20.330 Zero, one, two, three, four from the index. 07:20.630 --> 07:28.160 So here, if you write 5 or 10, in this case, we don't have that range or that index. 07:28.160 --> 07:32.810 And as you can see, list index out of range because we don't have that much item. 07:33.500 --> 07:38.810 So this is the result you want to users to see in this case, for example, Java, right. 07:39.260 --> 07:41.720 So nearly formatted output. 07:41.720 --> 07:48.060 So you can also use the string methods from previous lectures on any element. 07:48.070 --> 07:53.330 This list, for example, course topics that we will write here. 07:53.450 --> 08:01.210 So we have l strip lower upper let's upper and here, as you can see, we have uppercase Java. 08:01.220 --> 08:06.050 So Python here considers the first item. 08:06.050 --> 08:12.560 Actually, let me let me I want to explain this later because most new programmers. 08:13.390 --> 08:16.660 Have problem with this index thing here. 08:16.660 --> 08:25.270 So Python considers the first item in a list to be at a position zero. 08:25.270 --> 08:28.180 In the end, most programming language is actually considered like this. 08:28.180 --> 08:33.520 So here the car is worth zero, right? 08:33.910 --> 08:34.780 Zero. 08:37.490 --> 08:41.420 And this is not the first car is a zero at the index. 08:41.420 --> 08:44.330 This is true of most programming languages. 08:44.330 --> 08:51.070 And the reason has to do with how the list operations are implemented at a lower level. 08:51.080 --> 08:54.740 So if you are receiving an unexpected results. 08:56.150 --> 09:01.640 Ask yourself if you are making a simple but common off by one error. 09:01.730 --> 09:07.190 So the second item in the list has an index of. 09:07.880 --> 09:09.530 One of. 09:11.540 --> 09:16.310 The second item in the list has an index of one. 09:19.740 --> 09:20.220 Here. 09:20.610 --> 09:22.190 So let's make this. 09:23.580 --> 09:25.380 And the third item. 09:26.940 --> 09:30.630 As an index of two again. 09:34.740 --> 09:35.970 The fourth item. 09:37.290 --> 09:38.430 As the index. 09:39.370 --> 09:40.840 Of three. 09:42.430 --> 09:47.200 And the fifth item has an index of four. 09:49.070 --> 09:49.770 That's it. 09:49.790 --> 09:53.360 So this code here. 09:54.480 --> 09:55.260 For example. 09:55.260 --> 09:56.130 Now let's. 09:57.890 --> 09:58.430 Here. 09:58.700 --> 09:59.630 So. 10:03.030 --> 10:05.850 Now we will print here. 10:07.340 --> 10:08.300 Zero. 10:12.280 --> 10:15.010 Let's actually copy this again and again. 10:18.800 --> 10:19.020 Four. 10:19.070 --> 10:19.550 Five. 10:20.400 --> 10:20.850 So. 10:21.120 --> 10:25.260 Zero one, two, three, four. 10:26.750 --> 10:29.930 And here, as you can see here, this is our output, right? 10:29.960 --> 10:37.160 The 012 here, zero goes to here. 10:38.180 --> 10:44.090 The one goes to here, the three goes to here, the second line index. 10:44.090 --> 10:47.300 Of course, the fourth index goes to here. 10:47.300 --> 10:52.910 And digital forensics, the last index fourth goes to here. 10:53.090 --> 11:03.230 So the python has a special syntax for accessing the last element in a list if you ask for them at indexed 11:03.260 --> 11:07.310 index Z minus negative one here. 11:07.310 --> 11:08.810 Let's let's try this. 11:10.340 --> 11:11.420 This is the weird, right? 11:11.690 --> 11:15.170 And as you can see here, negative one. 11:16.610 --> 11:26.120 If you ask for the item at the index negative one python will always returns the last item. 11:26.120 --> 11:31.280 Negative one returns negative one. 11:32.610 --> 11:33.870 Returns. 11:37.660 --> 11:38.860 Returns. 11:42.040 --> 11:44.020 Returns the last item. 11:53.040 --> 11:53.280 Yeah. 11:53.760 --> 12:02.940 So here the the code returns the digital forensics and this syntax is quite useful because you will 12:02.940 --> 12:07.950 often want to access the last items in a list without knowing exactly how long the list is. 12:07.950 --> 12:17.100 So the convention extend other negative index values as well, and the index minus two returns the second 12:17.100 --> 12:19.140 item from the end of the list. 12:19.620 --> 12:20.250 Yeah. 12:21.090 --> 12:28.260 And the index minus three returns the third item from the end and so forth.