WEBVTT 00:01.000 --> 00:02.830 Hello and welcome back to the costs. 00:02.890 --> 00:06.810 So at the end of the last session we created our first list. 00:07.360 --> 00:08.470 So what is the list. 00:08.470 --> 00:14.370 A list is another object or data type that stores multiple other objects. 00:14.380 --> 00:22.360 So for example a list can store objects of different data types like integer US floats drinks and so 00:22.360 --> 00:22.630 on. 00:24.520 --> 00:27.520 So let's stop creating our first or second list. 00:28.480 --> 00:32.020 So we are opening and square brackets and. 00:32.050 --> 00:32.370 Yeah. 00:32.380 --> 00:37.080 We are storing for entered into just one two three far separated by a comma. 00:37.900 --> 00:41.110 And then let's see what happens if you're on the cell. 00:41.590 --> 00:45.790 So it returns back to a list with four elements. 00:45.790 --> 00:47.470 One two three four. 00:47.590 --> 00:54.630 And if you check the type of El then we get back on that list. 00:54.860 --> 01:00.500 And as I said before we can store elements of different data types. 01:00.510 --> 01:08.920 So for example here we had the US now and our next list M we store three float elements. 01:09.590 --> 01:16.910 So let's execute here the cell and we can see here we have a list m with one point five two point four 01:16.940 --> 01:19.040 and three point seven. 01:19.040 --> 01:22.220 And also we can create a list with String objects. 01:22.250 --> 01:31.130 So for example list n uh we have a dock or we have a card and we have a mouse and we can have a list 01:31.160 --> 01:33.140 where we have different data types. 01:33.140 --> 01:41.810 So for example list o contains an integer one that contains a flow two point far and contains the string 01:41.810 --> 01:45.910 object dark and it's no problem at works. 01:46.700 --> 01:49.010 And you can think of a list like a backpack. 01:49.010 --> 01:54.740 So for example if you go hiking you put into your bag a bottle of water sandwich two T-shirts and maybe 01:54.740 --> 01:57.340 a football and a yard. 01:57.680 --> 02:03.560 Everything fits into your bag and that's the same as with the list so you can actually put everything 02:03.590 --> 02:09.110 into a list and store it there and we saw on the last session that we can transform a string into a 02:09.110 --> 02:10.100 list. 02:10.100 --> 02:12.250 So for example we have the string. 02:12.260 --> 02:21.110 This is a string and we can transform it by calling the function list and we get back a list with all 02:21.110 --> 02:22.700 single elements of the string. 02:22.700 --> 02:24.080 So T H I. 02:24.080 --> 02:26.450 Also an empty space. 02:26.450 --> 02:33.190 And also here at the exclamation mark so let's check again what data type we have here follower list 02:33.190 --> 02:40.610 P and of course it's a list and we can also count the amount of elements in the list. 02:42.190 --> 02:44.110 So in this case it's 17. 02:44.120 --> 02:46.330 And yeah we can have we can count here. 02:46.810 --> 02:54.940 And um yeah as we had before also the empty spaces and the exclamation marks also a string and also 02:54.940 --> 02:56.380 count four for the length. 02:56.860 --> 03:00.480 So next we can take the arithmetic sum of all elements. 03:00.490 --> 03:08.830 So we take the sum of l let's check L is on the list with four integers so a sum of four integers should 03:09.290 --> 03:10.030 should work. 03:10.990 --> 03:19.120 So the sum of one two three four four is ten and you can also take the sum of list m s so getting again 03:19.180 --> 03:24.880 m here is the list that's floating floats. 03:24.880 --> 03:26.380 So this should also work. 03:28.670 --> 03:30.520 So it's seven point six. 03:30.860 --> 03:38.410 And we tried to take the sum of lists and so list n and list and contains strings. 03:38.900 --> 03:40.530 So the sum of strings. 03:40.670 --> 03:42.080 I'm not sure if this works 03:45.430 --> 03:47.490 no it doesn't work so it gives less than Iran. 03:49.270 --> 03:54.620 So let's get back to lists L in list l there are four integers one two three four. 03:54.640 --> 04:03.100 And um what we can do with S and method Bill and method for lists called append and there we can append 04:03.580 --> 04:05.910 another element to the end of the list. 04:06.010 --> 04:11.110 So if we append five let's see what happens. 04:11.230 --> 04:15.940 So then we get back a list with a five in the end. 04:15.940 --> 04:21.040 And if you repeat this process and call a pen one more time with them the element five. 04:21.100 --> 04:22.730 So we get another five. 04:23.620 --> 04:24.110 And. 04:24.160 --> 04:28.750 There's also a method that counts the number of occurrences of one element. 04:28.750 --> 04:35.950 So if you want to count the number of occurrences of element five we can do so by calling the method 04:35.950 --> 04:38.690 count that we have to. 04:38.720 --> 04:46.730 So we have two times um the element five and now we can also remove an element from a list by calling 04:46.730 --> 04:52.140 the method remove and in brackets we have the element we want to remove. 04:52.170 --> 04:54.220 And so we have fear. 04:54.260 --> 05:01.970 We want to remove five and we have two times five on our list and the method remove removes the first 05:02.030 --> 05:04.380 occurrence of an element. 05:04.400 --> 05:05.060 Let's check. 05:05.910 --> 05:06.190 Okay. 05:06.230 --> 05:15.200 So now we have only only if the five only ones and we can account again the five and s so we have one 05:15.200 --> 05:22.580 time we have five on our list and we can also reverse the sequence of our elements by calling the method 05:22.700 --> 05:25.220 reverse. 05:25.220 --> 05:26.200 So let's do this. 05:26.210 --> 05:31.850 And now you can see so before our the sequence of our lists was one two three four five and now we are 05:31.850 --> 05:39.600 half and the reverse sequence five four three two one and that's also a method called Sarge where we 05:39.600 --> 05:41.630 can start our list. 05:41.730 --> 05:49.710 So in the case where we have only integers in our list Python automatically thoughts from from low to 05:49.710 --> 05:50.100 high. 05:50.760 --> 05:51.840 So let's see what happens 05:56.160 --> 06:01.740 and there's also the possibility to reverse the order with the method thought. 06:01.770 --> 06:07.860 So that's apparently the called reverse and it's uh by default it's set to fall. 06:07.890 --> 06:15.770 But we can set it to true and now we affirm the reverse order and we can sort it again 06:18.820 --> 06:21.310 to the ascending order. 06:21.370 --> 06:22.680 So beginning with one. 06:24.650 --> 06:25.410 All right. 06:27.270 --> 06:33.980 And what we can also do we can add a list and a list so we have a list containing one two three four 06:33.980 --> 06:34.640 five. 06:34.680 --> 06:40.000 And we can add another list containing three integers six seven and eight. 06:40.980 --> 06:45.800 So now we have a combined or a concatenated list. 06:45.810 --> 06:47.790 One two three four five six seven eight. 06:47.790 --> 06:49.080 So we have eight elements. 06:49.080 --> 06:50.260 No one list. 06:51.000 --> 06:54.490 And what is not working actually so we cannot subtract two. 06:54.540 --> 06:55.320 Two lists. 06:55.320 --> 07:00.450 So that s guess less an error message. 07:00.450 --> 07:02.730 All right so let's go back to our initial list. 07:02.760 --> 07:08.430 So we have a list with five elements and let's try to multiply our list. 07:08.450 --> 07:14.510 Um with two and let's see what we get. 07:14.580 --> 07:18.270 So actually Python here it concatenate many copies. 07:18.300 --> 07:22.080 So in this case two copies and um yeah. 07:22.080 --> 07:25.010 As you can see this is not an element y's multiplication. 07:25.020 --> 07:32.640 So if you see at the times two you could also expect that uh one is uh multiplied by two two is multiplied 07:32.640 --> 07:33.630 by two. 07:33.690 --> 07:37.350 So that in the end we get two four six eight ten. 07:37.350 --> 07:41.460 But this is not the case so this is not our how lists work. 07:41.460 --> 07:50.560 So we just get many copies of the same lists here and uh for the sake of completeness um division of 07:50.590 --> 07:51.580 uh lists. 07:51.740 --> 07:52.870 An into us. 07:52.930 --> 07:55.180 Uh not possible. 07:55.180 --> 07:55.540 All right. 07:55.540 --> 07:57.720 So that's uh that's it for. 07:57.730 --> 08:03.700 For the time being and uh hope to see you again and lists parts 2 or so C in the next session by.