1 00:00:05,400 --> 00:00:07,290 Okay, so it's time for a challenge. 2 00:00:07,290 --> 00:00:10,120 This is the second challenge with dictionaries. 3 00:00:10,120 --> 00:00:12,510 Now we've mentioned that the data for 4 00:00:12,510 --> 00:00:16,110 this adventure game could be organized in many different ways. 5 00:00:16,110 --> 00:00:19,300 And we've created another way for you here in this code. 6 00:00:19,300 --> 00:00:21,920 So your mission, if you chose to accept it. 7 00:00:21,920 --> 00:00:24,240 Is to change the code below to make it work. 8 00:00:24,240 --> 00:00:29,010 Now, the code that is below is the complete program from the last video, 9 00:00:29,010 --> 00:00:33,470 the adventure game but with the location's dictionary modified so 10 00:00:33,470 --> 00:00:37,050 that everything is in a single dictionary. 11 00:00:37,050 --> 00:00:40,270 So what your job here if the challenge is to fix it ANd we'll go down and 12 00:00:40,270 --> 00:00:43,160 have a look at the code, and you'll notice there are some errors here. 13 00:00:43,160 --> 00:00:45,170 There's errors there that you'll need to fix. 14 00:00:45,170 --> 00:00:49,390 So you'll need to get this working because we've not got our descriptions for 15 00:00:49,390 --> 00:00:52,050 the various locations, nox, x, etc. 16 00:00:52,050 --> 00:00:54,760 All in the one sort of master dictionary. 17 00:00:54,760 --> 00:00:55,410 So that's your goal. 18 00:00:55,410 --> 00:00:58,540 Now the thing to remember with this challenge is there's not a lot of code you 19 00:00:58,540 --> 00:00:59,610 need to change. 20 00:00:59,610 --> 00:01:03,930 In fact you should only have to make changes to just four lines of code to 21 00:01:03,930 --> 00:01:04,830 get this to work. 22 00:01:04,830 --> 00:01:08,040 Now check any of your warnings carefully if you're using IntelliJ here. 23 00:01:08,040 --> 00:01:11,670 And don't worry if all four changes give you the same warning. 24 00:01:11,670 --> 00:01:14,250 We will explain why, in the solution. 25 00:01:14,250 --> 00:01:16,680 I'm gonna ask you to pause the video now, go away and 26 00:01:16,680 --> 00:01:18,360 see if you can solve this challenge. 27 00:01:18,360 --> 00:01:21,220 Once you're ready to come back and see the solution, click play and 28 00:01:21,220 --> 00:01:22,400 I'll be here showing you how to do it. 29 00:01:25,580 --> 00:01:28,790 Okay so, hopefully you managed to solve this. 30 00:01:28,790 --> 00:01:29,600 So, let's go through and 31 00:01:29,600 --> 00:01:34,300 show you our solution, and how we would go about fixing this. 32 00:01:34,300 --> 00:01:38,470 So the first thing we need to change here, the error is showing on line 43. 33 00:01:38,470 --> 00:01:43,910 So, clearly the problem there is it's trying to use the exits dictionary, 34 00:01:43,910 --> 00:01:45,780 which no longer exists. 35 00:01:45,780 --> 00:01:47,600 So, we need to change the code. 36 00:01:47,600 --> 00:01:49,620 To use our master dictionary. 37 00:01:49,620 --> 00:01:52,830 So what need to do there is we still need to join it, so availableExits, 38 00:01:52,830 --> 00:01:57,210 that first part is correct but the join now is not exits rather it's on locations. 39 00:01:57,210 --> 00:02:03,300 So we type locations[loc] but then We need to put 40 00:02:03,300 --> 00:02:07,990 exits to use the exits component of the dictionary, and dot keys. 41 00:02:07,990 --> 00:02:12,080 So that's the first change, pretty simple change as you can see. 42 00:02:12,080 --> 00:02:16,210 So we're looking up the key exits and grabbing the keys for those. 43 00:02:16,210 --> 00:02:19,760 Which is now, of course, all enclosed in one master dictionary. 44 00:02:19,760 --> 00:02:22,290 Of which we've got subdictionaries built in. 45 00:02:22,290 --> 00:02:25,280 So we've still got a room location, so you can see there, 46 00:02:25,280 --> 00:02:29,840 the number equated to each room, but we've now got two entries. 47 00:02:29,840 --> 00:02:31,650 Before we had a single dictionary. 48 00:02:31,650 --> 00:02:35,940 We've got D E S C, which is the description for the location and 49 00:02:35,940 --> 00:02:41,230 also got exits Which is our valid exit in the named exits. 50 00:02:41,230 --> 00:02:45,230 So we've separated the three variables that we had, three separate dictionaries 51 00:02:45,230 --> 00:02:47,990 and we put those dictionaries into this one master dictionary. 52 00:02:47,990 --> 00:02:49,090 So each location, 53 00:02:49,090 --> 00:02:52,790 in essence, has now We got three dictionaries as you can see there. 54 00:02:52,790 --> 00:02:53,870 So it's a little bit confusing. 55 00:02:53,870 --> 00:02:59,100 So we got one master as you can see there which contains the description, the exits 56 00:02:59,100 --> 00:03:04,040 and the main exits and of course exits and main exits are themselves dictionaries. 57 00:03:04,040 --> 00:03:08,530 So there's three dictionaries there in total as we can see effectively for 58 00:03:08,530 --> 00:03:09,100 each location. 59 00:03:09,100 --> 00:03:10,760 So a little bit confusing. 60 00:03:10,760 --> 00:03:12,880 But that's the gist of it anyway. 61 00:03:12,880 --> 00:03:16,540 OK, so that was the first fix, so now what we're doing is we're correctly 62 00:03:16,540 --> 00:03:19,510 looking up lock, which is finding the relevant location number, 63 00:03:19,510 --> 00:03:23,000 then we're looking up the exits, so we're using that lookup there to find that 64 00:03:23,000 --> 00:03:28,180 particular dictionary, then using the dot keys to get all the keys that exist for 65 00:03:28,180 --> 00:03:31,380 that particular entry This case which is exits. 66 00:03:31,380 --> 00:03:34,600 So that's the first fix, so I'll just come back here again, 67 00:03:34,600 --> 00:03:39,260 it's got another problem there, print locations, loc isn't going to work. 68 00:03:39,260 --> 00:03:42,580 What we need to do is also use the descriptions. 69 00:03:42,580 --> 00:03:46,190 We need to look that up to make sure we're grabbing it from the right spot. 70 00:03:46,190 --> 00:03:50,430 So I'd need to use that key to retrieve it, so 71 00:03:50,430 --> 00:03:55,810 to do that, we just put, as you can see. 72 00:03:55,810 --> 00:04:00,250 And then that will now correctly find us the description for the location. 73 00:04:01,520 --> 00:04:05,070 So that's two fixes, now these errors here on line 50 and 74 00:04:05,070 --> 00:04:08,970 51 also have to be fixed, and in the first one you'll probably guess that because 75 00:04:08,970 --> 00:04:14,010 it's very similar to what we did on line 43, so we're no longer using the Exits 76 00:04:14,010 --> 00:04:18,370 dictionary as a separate variable, it's now part of our master dictionary So 77 00:04:18,370 --> 00:04:20,950 to fix that, we'll change that to locations. 78 00:04:22,100 --> 00:04:25,320 Loc and then it's going to be exits. 79 00:04:27,760 --> 00:04:28,380 Like so. And 80 00:04:28,380 --> 00:04:31,780 that's now grabbing the exits dictionary and then taking a copy of that. 81 00:04:31,780 --> 00:04:34,930 And likewise, on the next line, you can probably get that with named exits. 82 00:04:34,930 --> 00:04:37,360 We no longer have a separate variable for that. 83 00:04:37,360 --> 00:04:39,150 So we need to fix that as well. 84 00:04:39,150 --> 00:04:42,270 So we're going to leave name exits in because we're gonna use that part of it. 85 00:04:42,270 --> 00:04:48,870 But we're going to make it locations lock, and 86 00:04:49,870 --> 00:04:55,750 then it's going to be, named exits, like so. 87 00:04:57,150 --> 00:04:59,010 We can get rid of the rest of that line now. 88 00:04:59,010 --> 00:05:01,900 And of course I made a typo there so that shouldn't be in there. 89 00:05:01,900 --> 00:05:02,810 Let's fix that up. 90 00:05:02,810 --> 00:05:04,070 So that should now be it. 91 00:05:04,070 --> 00:05:06,770 That should be all we need to run this. 92 00:05:06,770 --> 00:05:08,510 So let's just run it and make sure it works. 93 00:05:13,920 --> 00:05:17,440 We correctly not getting our numbers for the available exits so that's good, 94 00:05:17,440 --> 00:05:18,550 that part's working. 95 00:05:18,550 --> 00:05:23,990 Then we can type go west, you're at the top of a hill, we can go type in road. 96 00:05:23,990 --> 00:05:26,940 Can't go in that direction, which is correct because of where we are, 97 00:05:26,940 --> 00:05:31,360 we can go north You're in the forest, control, type in road again. 98 00:05:31,360 --> 00:05:34,680 You are standing at the end of a road before a small brick building. 99 00:05:34,680 --> 00:05:35,920 We should be able to enter hill. 100 00:05:35,920 --> 00:05:37,970 You are at the top of a hill. 101 00:05:37,970 --> 00:05:40,410 And you can see the available exits are working. 102 00:05:40,410 --> 00:05:41,500 Quit out of that. 103 00:05:41,500 --> 00:05:43,220 You are sitting at a computer learning python. 104 00:05:43,220 --> 00:05:44,670 I'm going to close this down again. 105 00:05:46,410 --> 00:05:47,480 And we could also put in here, 106 00:05:47,480 --> 00:05:50,720 if we wanted to, plus just a space there if we wanted to. 107 00:05:50,720 --> 00:05:51,590 So let me run it. 108 00:05:52,680 --> 00:05:54,770 We've now got that extra space there. 109 00:05:54,770 --> 00:05:56,480 So that's the challenge. 110 00:05:56,480 --> 00:05:57,580 Clean up the errors now. 111 00:05:57,580 --> 00:06:01,040 The lint checker in IntelliJ is complaining, and PyCharm will do the same. 112 00:06:01,040 --> 00:06:01,940 It's gonna show a warning. 113 00:06:01,940 --> 00:06:07,300 So if we come over here and select them, expected type int matching generic types. 114 00:06:07,300 --> 00:06:09,520 And we'll just click on that to see which line it's talking about. 115 00:06:09,520 --> 00:06:11,350 You can see it's line 43. 116 00:06:11,350 --> 00:06:15,730 I should put an arrow fix in there to fix it up, like so. 117 00:06:15,730 --> 00:06:18,720 And the other arrows relate to the two other lines that we actually worked on. 118 00:06:18,720 --> 00:06:22,370 And you can see it's having the same problems as you can see there. 119 00:06:22,370 --> 00:06:26,700 So these are the four lines that we've modified that Intelliga is 120 00:06:26,700 --> 00:06:30,530 saying coming up with a problem, potentially a problem showing a warning. 121 00:06:30,530 --> 00:06:34,800 So the problem is it's complaining that it expected an int, but got a string instead. 122 00:06:34,800 --> 00:06:38,930 So generally speaking, the lint checker, and that's what this process is, 123 00:06:38,930 --> 00:06:41,810 does a really good job of checking your code as you type it. 124 00:06:41,810 --> 00:06:43,610 But that said, it's not perfect. 125 00:06:43,610 --> 00:06:48,020 So the hint does say to press control F1, command F1 on a Mac. 126 00:06:48,020 --> 00:06:51,760 And we get the full message, and basically due to dynamic dispatch and 127 00:06:51,760 --> 00:06:56,390 duck typing, This is possible in a limited, but useful, number of cases. 128 00:06:56,390 --> 00:06:58,660 Now [LAUGH] that's a bit of a cryptic message and 129 00:06:58,660 --> 00:07:00,270 I'll just bring that up on the screen again. 130 00:07:00,270 --> 00:07:04,320 Again, due to dynamic dispatch and duck typing, this is possible in a limited but 131 00:07:04,320 --> 00:07:05,680 useful number of cases. 132 00:07:05,680 --> 00:07:08,520 But as it turns out, this is one of those useful cases. 133 00:07:08,520 --> 00:07:12,040 Nesting dictionaries, as we've done here for the locations dictionary. 134 00:07:12,040 --> 00:07:12,900 Is quite advanced. 135 00:07:12,900 --> 00:07:16,200 So, congratulations if you've worked out the solution. 136 00:07:16,200 --> 00:07:19,810 And, because we're using string keys, lint's finding it hard to cope. 137 00:07:19,810 --> 00:07:21,640 Now, obviously the program runs, so 138 00:07:21,640 --> 00:07:23,560 the path in itself is quite happy with the syntax. 139 00:07:23,560 --> 00:07:25,720 So, it's more the lint checker here. 140 00:07:25,720 --> 00:07:28,900 Now incidentally, the reference to duck typing Is the path and 141 00:07:28,900 --> 00:07:29,970 why of doing things. 142 00:07:29,970 --> 00:07:32,970 As far as path is concerned, if it quacks like a duck, then it is a duck. 143 00:07:32,970 --> 00:07:37,690 So in other words, since path is dynamically typed, 144 00:07:37,690 --> 00:07:41,190 then we said that before, and it's more interested in the behavior of things 145 00:07:41,190 --> 00:07:44,540 than actually than being declared As a particular type. 146 00:07:44,540 --> 00:07:46,120 And that's a good thing. 147 00:07:46,120 --> 00:07:48,320 Because, of course, there's no type declarations in path. 148 00:07:48,320 --> 00:07:52,560 So the bottom line is that although the IntelliJ checker expects named exits, 149 00:07:52,560 --> 00:07:54,090 in this case, to be an integer index. 150 00:07:54,090 --> 00:07:55,630 And I'm talking about this part, here. 151 00:07:55,630 --> 00:07:56,950 For example, on line 51. 152 00:07:56,950 --> 00:08:00,450 So although it's expecting that and preferring that to be an integer index, 153 00:08:00,450 --> 00:08:04,190 Python itself knows that the location's like this component. 154 00:08:05,500 --> 00:08:06,740 It knows that that's a dictionary and 155 00:08:06,740 --> 00:08:10,680 it's happy to accept a string key into it because of the way we've defined it. 156 00:08:10,680 --> 00:08:14,600 So this is one of those sort of relatively rare cases, where the checker isn't really 157 00:08:14,600 --> 00:08:18,180 right in its explanations or when it's telling us that we've got something wrong. 158 00:08:18,180 --> 00:08:20,590 There isn't a problem with the way we've developed the code here. 159 00:08:20,590 --> 00:08:21,430 All right, so that's it. 160 00:08:21,430 --> 00:08:24,500 We're finally now done with dictionaries, and again, congratulations if you did 161 00:08:24,500 --> 00:08:29,480 figure this out because it's getting to be quite advanced code figuring out 162 00:08:29,480 --> 00:08:32,679 solutions to dictionaries within dictionaries as we've actually got here. 163 00:08:32,679 --> 00:08:34,980 So we're going to move on from dictionaries now. 164 00:08:34,980 --> 00:08:38,140 In the next video we're going to start work on sets. 165 00:08:38,140 --> 00:08:39,200 So, see you in that next video.