1 00:00:04,910 --> 00:00:09,180 Continuing with tuples_intro.py, it would be useful to store 2 00:00:09,180 --> 00:00:13,799 all our albums in a single list. Now if we're going to do that, we must enclose 3 00:00:13,799 --> 00:00:18,780 each one in parentheses. I suggested always using parentheses around your 4 00:00:18,780 --> 00:00:24,640 tuples, and you can see that I didn't do that in the five tuples on lines 1 to 5. 5 00:00:24,640 --> 00:00:28,640 What we'll do first is create the list without any parentheses, to show you 6 00:00:28,650 --> 00:00:33,360 why they're necessary. So I'm going to go ahead and change this to; welcome's 7 00:00:33,360 --> 00:00:39,120 gonna be changed to albums. I'm going to put our left square bracket there. 8 00:00:39,120 --> 00:00:47,820 I'm going to put a comma at the end of each line. We're going to put our right 9 00:00:47,820 --> 00:00:52,980 square bracket at the start of line six and then I'm going to delete the variable 10 00:00:52,980 --> 00:01:01,700 definitions at the start - each one of these, like so. 11 00:01:01,700 --> 00:01:04,640 I'm going to delete all the code after that closing brace, the right 12 00:01:04,650 --> 00:01:08,910 square bracket. That's only going to, that was referring to variables that we don't 13 00:01:08,910 --> 00:01:12,660 have anymore and was showing an error. Alright, so what we've got now 14 00:01:12,660 --> 00:01:18,630 looks like a list containing five albums. It doesn't conform to the Python style 15 00:01:18,630 --> 00:01:22,680 guide, so what we should do is reformat the code before going any further. So I'm 16 00:01:22,680 --> 00:01:27,860 gonna come up to code and select Reformat Code. You can use the shortcut if you prefer. 17 00:01:27,860 --> 00:01:31,860 Now that I've done that, it looks even more like a list containing five albums, 18 00:01:31,860 --> 00:01:39,820 but in fact, it's not. What it is, is a list containing 15 items, 10 strings and 5 ints. 19 00:01:39,820 --> 00:01:42,810 Just adding line breaks doesn't make each group of entries into 20 00:01:42,810 --> 00:01:48,510 a tuple. We need to use parentheses to do that. Now we can check, by printing out 21 00:01:48,510 --> 00:01:51,340 how many items are on the list. So let's do that. 22 00:01:51,340 --> 00:01:59,100 On line 8, I'm going to type print parentheses len parentheses albums. 23 00:01:59,100 --> 00:02:03,720 Run the program and the answer will be 15, as you can see on the screen there. When we 24 00:02:03,720 --> 00:02:06,990 use parentheses around the individual album details, we will get a list 25 00:02:06,990 --> 00:02:11,380 containing five entries. So let's have a go at doing that. So we're gonna each one of 26 00:02:11,380 --> 00:02:16,180 these groups here, up to but not including the furthermost right comma, 27 00:02:16,180 --> 00:02:19,520 we're gonna surround in parentheses. 28 00:02:36,200 --> 00:02:40,920 Alright, like so. So now that I've done that, at the end of each line, the comma 29 00:02:40,920 --> 00:02:44,880 separates the tuple from the next one. So do make sure you put the comma 30 00:02:44,880 --> 00:02:49,170 after the closing parenthesis, as I did, or you'll get an error. So run the program - 31 00:02:49,170 --> 00:02:55,060 this time we should see the answer 5, instead of 15, and you can see that's the case. 32 00:02:55,060 --> 00:03:00,360 Our albums list now contains five tuples, and each of those tuples contains 33 00:03:00,360 --> 00:03:05,120 three items. Now if we want to print out a catalogue of all our albums, 34 00:03:05,120 --> 00:03:10,240 all we need to do is iterate over the list. Let's have a go at doing that. 35 00:03:10,240 --> 00:03:20,040 So on line 10, I'm going to type for album in albums : and on the next line, print 36 00:03:20,040 --> 00:03:28,880 parentheses double quotes Album : Then we want left and right curly braces comma 37 00:03:28,880 --> 00:03:35,480 Artist : left and right curly braces again comma Year : 38 00:03:35,480 --> 00:03:39,660 left and right curly braces, closing double quote. On the next line, I'm going to 39 00:03:39,660 --> 00:03:52,980 type dot format and it's going to be, in parentheses, album 0 album 1, in square 40 00:03:52,980 --> 00:04:01,440 brackets again, and finally, album 2 in square brackets, and we've got our two 41 00:04:01,440 --> 00:04:07,049 right parentheses as well. And I split line 11 up, just to make it easier to see 42 00:04:07,049 --> 00:04:12,540 on the screen. You don't need to do that. Run the program, and we should see our 43 00:04:12,540 --> 00:04:16,168 tuples printed out - our albums, I should say - from the tuples, and we can see them 44 00:04:16,168 --> 00:04:21,860 on screen there. Now this would be tidier - the code that I just wrote - if we unpacked 45 00:04:21,860 --> 00:04:26,620 the tuple and used sensibly named variables for the album name, 46 00:04:26,620 --> 00:04:31,980 artist and year. So in other words, changing it so we had something like this; 47 00:04:31,980 --> 00:04:39,600 we're going to make this name change there, to name comma artist, comma year. 48 00:04:39,600 --> 00:04:41,100 Now you can see the errors on the screen 49 00:04:41,100 --> 00:04:45,300 because we haven't unpacked the tuples yet. I know I haven't unpacked them either. 50 00:04:45,300 --> 00:04:49,140 I'll be doing that in the next lecture. Before that, your challenge is to 51 00:04:49,140 --> 00:04:53,430 fix the errors in the most efficient way you can think of. So the challenge is to 52 00:04:53,430 --> 00:04:58,590 fix the errors in our code, by unpacking the tuples into the variables, that we're 53 00:04:58,590 --> 00:05:03,330 using on line 12. Now, there are two ways that you could do that. Try to do it by only 54 00:05:03,330 --> 00:05:10,080 changing one line of code. In any event, I'll go over my solution in the next video.