1 00:00:04,680 --> 00:00:09,600 We've seen how to join items in an iterable, using the join method. 2 00:00:09,600 --> 00:00:15,140 Strings have an opposite method - the split method. We called our last Python 3 00:00:15,150 --> 00:00:18,780 file joining_things, so let's create a new one, and I'm going to call 4 00:00:18,780 --> 00:00:22,550 this one splitting_ things. 5 00:00:30,720 --> 00:00:34,700 The split method splits a string up into words. 6 00:00:34,700 --> 00:00:38,880 Now that sounds simple, so let's see it working. So I'm gonna start by typing 7 00:00:38,880 --> 00:00:48,240 panagram is equal to, and in double quotes, The quick brown fox jumps over 8 00:00:48,240 --> 00:00:59,640 the lazy dog. On line three, I'm going to type words is equal to panagram.split, 9 00:00:59,640 --> 00:01:04,080 leaving the parentheses in so we're calling the method. On line four I'm 10 00:01:04,080 --> 00:01:13,420 just going to print out words, so print, words in parentheses. When we run that, 11 00:01:13,420 --> 00:01:18,780 we get a list containing all the words in the string. We didn't provide any 12 00:01:18,790 --> 00:01:23,140 arguments to split, so it defaults to splitting on whitespace. Whitespace 13 00:01:23,140 --> 00:01:27,040 includes things like tabs and newlines, as well as a few other characters, 14 00:01:27,040 --> 00:01:31,660 including the space. So to demonstrate that, what I'll do is use triple quotes 15 00:01:31,660 --> 00:01:35,540 and space the string over several lines. Let's go ahead and do that. 16 00:01:35,540 --> 00:01:40,620 We've got three quotes at the start here, and two down the end, and we're gonna space 17 00:01:40,630 --> 00:01:45,850 it over multiple lines, as I said. So I'm going to press ENTER after brown and 18 00:01:45,850 --> 00:01:52,420 move the space. In between the word jumps and over, I'm going to put a tab, \t, 19 00:01:52,420 --> 00:01:57,429 I'm gonna press ENTER after the word over, so you can see we've spaced that, now, 20 00:01:57,429 --> 00:02:03,970 over three lines. So if I run that, and you can see we get exactly the same 21 00:02:03,970 --> 00:02:09,960 output, a list containing all nine words of the string. Split returns a list. 22 00:02:09,960 --> 00:02:14,140 You call it on a string and it returns all the items in the string, that are 23 00:02:14,140 --> 00:02:19,660 separated by one or more whitespace characters. That's the default behaviour, 24 00:02:19,660 --> 00:02:23,120 but it also has a couple of named arguments. 25 00:02:23,120 --> 00:02:26,880 I won't call up the documentation in a browser. You've got the page bookmarked 26 00:02:26,890 --> 00:02:31,360 and you can refer to that after this video, if you wish. Sometimes, you'll just 27 00:02:31,360 --> 00:02:35,940 want a quick reminder of the parameters that a function or method defines. 28 00:02:35,940 --> 00:02:40,440 The JetBrains IDEs - IntelliJ and Pycharm - have a useful feature to let 29 00:02:40,450 --> 00:02:47,019 you do that. Holding down the control key, and hover over the method. You can see 30 00:02:47,019 --> 00:02:51,220 I'm doing that for split, there. Now on a Mac you'll use the command key, and also 31 00:02:51,220 --> 00:02:55,989 most modern IDs will also have a similar feature. So as you can see, that's a 32 00:02:55,989 --> 00:03:00,459 useful way to get a quick reminder about the arguments you can use, as well as the 33 00:03:00,460 --> 00:03:05,260 names of named arguments. The first parameter you can see there is called self. 34 00:03:05,260 --> 00:03:08,620 Now this might sound strange, but I'm going to ask you to pretend that 35 00:03:08,620 --> 00:03:11,799 isn't there for the moment. One difference between a function and a 36 00:03:11,799 --> 00:03:16,510 method, is a presence of this self parameter. You'll learn all about that in 37 00:03:16,510 --> 00:03:21,430 the Object-Oriented Programming section of this course. When you're using the 38 00:03:21,430 --> 00:03:26,840 methods, Python provides a value for self for you, so don't worry about it at the moment. 39 00:03:26,840 --> 00:03:31,030 So moving on next, we can see the sep named argument. That's used to decide 40 00:03:31,030 --> 00:03:35,590 what separates the words in the string. As I've said previously, the default is 41 00:03:35,590 --> 00:03:39,519 whitespace, but you may have a comma separated list, for example, that you want 42 00:03:39,519 --> 00:03:45,040 to split. In that case, you can provide a comma as the separator. If you recall, 43 00:03:45,040 --> 00:03:48,850 we saw an example of that way back in section 4, when we extracted all the 44 00:03:48,850 --> 00:03:52,569 values from a string. So let's go through that again. We had a string containing 45 00:03:52,569 --> 00:04:03,580 digits separated by commas. So I'm going to type on line 8, numbers is equal to 9 comma 46 00:04:03,580 --> 00:04:16,260 223,372,O36,854,775 and 807. We can tell split to split the 47 00:04:16,269 --> 00:04:20,769 string up at the commas, to get a list of just sequences of digits. So I could type 48 00:04:20,769 --> 00:04:25,030 print, in parentheses I can type numbers 49 00:04:25,030 --> 00:04:29,950 dot split parentheses and this time, within the parentheses, I'm going to put 50 00:04:29,950 --> 00:04:37,990 a comma in double quotes. So run the program - you can see, we've got a list 51 00:04:37,990 --> 00:04:42,610 there, containing each of the numbers from our number string. Now note that 52 00:04:42,610 --> 00:04:47,560 they're all strings. When you split a string, you get a list of strings. That's 53 00:04:47,560 --> 00:04:51,639 why I had to use that strange code, back in section 4. I wanted to add up all the 54 00:04:51,639 --> 00:04:56,470 values, so they had to be converted to integers first. You'll understand what 55 00:04:56,470 --> 00:05:00,560 that code was doing, later in the course. It's basically, a more concise way 56 00:05:00,560 --> 00:05:05,300 of writing the code that you will create for the challenge, at the end of this video. 57 00:05:05,300 --> 00:05:08,400 Now there was another strange bit of code in that example. I'm going to 58 00:05:08,410 --> 00:05:13,930 paste that back in here, so we can talk about it. Now don't bother typing that 59 00:05:13,930 --> 00:05:17,140 code in because I'm not going to run it. I just want to show you how we used 60 00:05:17,140 --> 00:05:21,250 split in that earlier example. It won't run in any case, at the moment. We've got 61 00:05:21,250 --> 00:05:25,510 an error because separators isn't defined. You should have the complete 62 00:05:25,510 --> 00:05:28,440 code in the strings2.py file from the last section, 63 00:05:28,440 --> 00:05:32,580 if you want to refer back to it. But looking at the code on line 11, we used 64 00:05:32,590 --> 00:05:37,180 the join and split commands. The line still won't make complete sense because 65 00:05:37,180 --> 00:05:41,800 of that strange code that we're passing to join. What I'll do, though, is replace 66 00:05:41,800 --> 00:05:47,080 the code with the sequence that it produces. Okay, so the strange code on 67 00:05:47,080 --> 00:05:52,690 line 11, produced the generated list on lines 12 to 18, so it, basically, replaced 68 00:05:52,690 --> 00:05:58,000 all the separators with spaces and produce the list of all the characters. 69 00:05:58,000 --> 00:06:01,780 And you'll learn how that worked later. We can now start, now, to make sense of 70 00:06:01,780 --> 00:06:07,540 how join and split were being used together. Let's focus on the join part first, 71 00:06:07,540 --> 00:06:12,100 and what I'll do is, I'll just comment out line 11 now. Alright, so 72 00:06:12,100 --> 00:06:19,000 let's focus on the join part of line 19, first. First we're gonna start by deleting 73 00:06:19,000 --> 00:06:23,320 the dot split on the end of that line, like so, and we'll add it back shortly. 74 00:06:23,320 --> 00:06:29,580 First though, let's see what join produces, so let's run on the program. We've called 75 00:06:29,590 --> 00:06:35,800 join on an empty string on line 19. That means the items in the list won't be 76 00:06:35,800 --> 00:06:40,320 separated from each other by anything. Remember that the string you use 77 00:06:40,320 --> 00:06:45,300 when calling join, is used to separate the items that you're joining. So we end up 78 00:06:45,300 --> 00:06:50,060 with a string containing all the items from generated list, 79 00:06:50,060 --> 00:06:55,040 essentially, from our generated list there, on line 12. All the items were single 80 00:06:55,050 --> 00:06:58,229 characters, and that's what we've got in our output - a string containing the 81 00:06:58,229 --> 00:07:02,669 single characters from the list. Each sequence of digits was followed by a 82 00:07:02,669 --> 00:07:07,289 space, and we get those spaces in our output. And again, I'll just run it 83 00:07:07,289 --> 00:07:11,879 again so we can see it. Alright, so the next thing we want to do is split that string 84 00:07:11,879 --> 00:07:16,319 up again. We know that split will split on whitespace, and we can see the spaces 85 00:07:16,320 --> 00:07:23,000 in the string, on the last line of our output. So let's add some code, so down here, 86 00:07:23,000 --> 00:07:31,180 on line 22, I'm going to type values_list is equal to values.split(), 87 00:07:31,180 --> 00:07:37,680 so I'm calling the split function. Then we'll print out the value, or values_list, 88 00:07:37,680 --> 00:07:41,520 or the contents, I should say, our values_list on the next line. 89 00:07:41,520 --> 00:07:45,120 So we haven't provided a separator when we call .split, so it 90 00:07:45,120 --> 00:07:50,060 splits up the string at the spaces, and if we run this, 91 00:07:52,400 --> 00:07:56,570 we can see that the last line of the output is a list, containing each of the 92 00:07:56,570 --> 00:08:01,100 numbers that appeared in the string. And we can see the string, on the line above that, 93 00:08:01,100 --> 00:08:05,840 in the output. Alright, so that's the join and split methods; join will let 94 00:08:05,840 --> 00:08:10,130 you create a string from a sequence, such as a list split. Split, on the other hand, will 95 00:08:10,130 --> 00:08:14,449 split the string up again and create a list. We'll be using these methods again, 96 00:08:14,449 --> 00:08:18,710 in some of the later examples. Split can be very useful when reading data from a 97 00:08:18,710 --> 00:08:23,479 file, for example. Experiment with your own lists and strings, and make sure you 98 00:08:23,480 --> 00:08:28,640 understand how to use these two methods before continuing. For now, though, 99 00:08:28,640 --> 00:08:32,679 let's finish this video with a mini-challenge. So looking at that last line of output, 100 00:08:32,679 --> 00:08:37,400 we've got a list of strings. Back in section 4, I used a comprehension 101 00:08:37,400 --> 00:08:42,340 to convert that to a list of numbers. We haven't covered comprehensions yet, but 102 00:08:42,340 --> 00:08:46,780 we have covered everything you need, to produce a list of ints. So your challenge is 103 00:08:46,780 --> 00:08:51,920 to use a for loop, to replace all the strings in that list with integer values. 104 00:08:51,920 --> 00:08:54,680 So what I'm going to do is close down the run window. So I'm going to paste in 105 00:08:54,680 --> 00:08:59,350 the comments now - the challenge in a series of comments, as you can see there. 106 00:08:59,350 --> 00:09:03,700 So that's the challenge. See how you go with it, and I'll go over my solutions to 107 00:09:03,700 --> 00:09:07,500 that challenge in the next video.