1 00:00:05,200 --> 00:00:11,840 In the last video, we successfully parsed the data in our country_info text file. We read the file, 2 00:00:11,840 --> 00:00:17,280 and created lists for each country, containing the seven pieces of information for each one. 3 00:00:17,280 --> 00:00:20,960 In this video, we'll put that data into a more useable format. 4 00:00:20,960 --> 00:00:24,800 When you're doing something like this, you'll usually have some goal in mind. 5 00:00:24,800 --> 00:00:29,600 Our goal, for this example, will be to find information on any country, using either the 6 00:00:29,600 --> 00:00:35,520 name of the country, or its two-letter ISO code. These two and three-letter codes, by the way, 7 00:00:35,520 --> 00:00:41,840 are defined by the International Standards Organisation, in ISO-3166. I'll put a link to 8 00:00:41,840 --> 00:00:47,280 that standard, in the resources for this video. Before we create the dictionary that we'll use, 9 00:00:47,280 --> 00:00:50,325 it would be nice to put all these fields into variables. 10 00:00:50,400 --> 00:00:54,080 That's easy to do, we can unpack the list for each country. 11 00:00:54,080 --> 00:00:57,745 There are seven fields, so we'll use seven variables. 12 00:01:11,440 --> 00:01:15,000 This is why it's essential that every line in the file contains seven fields – 13 00:01:15,000 --> 00:01:19,200 even if some fields are blank. If a list had fewer than seven items, 14 00:01:19,200 --> 00:01:23,200 our code would crash when we tried to unpack it into seven variables. 15 00:01:23,200 --> 00:01:27,680 Ok, next we'll print the variables, just to make sure everything's working. 16 00:01:27,680 --> 00:01:30,172 I'll replace the print on line 7: 17 00:01:51,844 --> 00:01:55,529 I've used a newline followed by a tab, for the separator. 18 00:01:55,529 --> 00:01:59,665 That should make the output a bit clearer, as you'll see when we run the program: 19 00:02:01,040 --> 00:02:04,240 Scroll up through the output, and the country name appears first, 20 00:02:04,240 --> 00:02:08,160 with the details about each country indented, on a new line. 21 00:02:08,160 --> 00:02:11,769 Scroll until you can see the details for "Antarctica". 22 00:02:13,680 --> 00:02:17,923 Four of the fields are empty, but we still had to parse them out of the data. 23 00:02:17,923 --> 00:02:21,125 That's why we had the separators, with nothing between them. 24 00:02:21,520 --> 00:02:26,256 Right at the top of the output, the first row in the file contained the headings for the fields. 25 00:02:26,320 --> 00:02:30,617 That can be useful, but we don't want to include those entries in our dictionary. 26 00:02:30,617 --> 00:02:35,120 The simplest way to exclude them, is to read that first line, before we iterate over the 27 00:02:35,120 --> 00:02:40,046 remainder of the file. I'll add a call to the readline method, before the loop: 28 00:02:44,960 --> 00:02:49,025 I'd better explain what's happening there, because it might not be obvious. 29 00:02:49,025 --> 00:02:54,578 Our country_file object is iterable. Each time you use the readline method to read a line, 30 00:02:54,578 --> 00:03:00,556 the iterator automatically moves on to the next item. That's the next line, in this case. 31 00:03:00,556 --> 00:03:05,680 So our for loop, on line 5, starts with the second line of the file – because we've already read the 32 00:03:05,680 --> 00:03:09,944 first line, on line 4. Run the program again, 33 00:03:11,280 --> 00:03:14,274 And scroll back up to the top of the output again. 34 00:03:16,160 --> 00:03:20,480 The first entry is now "Afghanistan", and we've skipped the field headings. 35 00:03:20,480 --> 00:03:24,914 Alright, on with the code. We've got the fields in variables, 36 00:03:24,914 --> 00:03:29,440 and we can use them to create a dictionary. We don't need line 8, now that we know the code 37 00:03:29,440 --> 00:03:33,144 is working, so I'll comment that line out first: 38 00:04:27,140 --> 00:04:29,600 I don't think I need to explain that code. 39 00:04:29,600 --> 00:04:34,240 We create a dictionary, using the values that we unpacked from the line of text. 40 00:04:34,240 --> 00:04:39,085 Run the program, to check that the dictionaries are what we expect. 41 00:04:41,767 --> 00:04:45,120 That's looking good. Now what do we do with them? 42 00:04:45,120 --> 00:04:49,600 Each of these dictionaries will let us get a particular piece of information for a country. 43 00:04:49,600 --> 00:04:52,640 What we need now, is some way to choose the country. 44 00:04:52,640 --> 00:04:56,640 We'll start by choosing a country by name. That means we need to put each of these 45 00:04:56,640 --> 00:05:00,640 dictionaries in another dictionary, with the key being the country name. 46 00:05:00,640 --> 00:05:04,792 I'll define the dictionary at the start of the code, before we open the file: 47 00:05:09,360 --> 00:05:14,078 We've now got an empty dictionary, and we can add each entry, inside the loop: 48 00:05:32,800 --> 00:05:36,720 We should end up with a dictionary where each of the keys are the name of a country, and the values 49 00:05:36,720 --> 00:05:41,196 are the dictionary for that country. We'll have a dictionary containing dictionaries – 50 00:05:41,196 --> 00:05:44,871 which we've seen before. Run the program 51 00:05:46,320 --> 00:05:49,520 and check the last line of the output. It's quite long, 52 00:05:49,520 --> 00:05:53,351 so you'll need to scroll sideways to get a feel for the contents. 53 00:05:57,280 --> 00:06:02,640 Ok, it's time for a challenge. This challenge is intended to make 54 00:06:02,640 --> 00:06:06,640 sure you understand the data that we've created, from our text file. 55 00:06:06,640 --> 00:06:10,720 The best way to understand it is to work with it, so that's what you'll be doing. 56 00:06:10,720 --> 00:06:13,680 The challenge is to get a country name from the user, then display 57 00:06:13,680 --> 00:06:18,560 the capital city for the chosen country. If you struggle, you may want to review the videos 58 00:06:18,560 --> 00:06:28,960 about dictionaries, in the previous section. I'll go over my solution, in the next video.