1 00:00:00,180 --> 00:00:02,490 Now, let us briefly talk about dictionaries. 2 00:00:03,300 --> 00:00:08,250 So dictionaries are not that important for us in this course, but still they are an important part 3 00:00:08,250 --> 00:00:08,850 of Python. 4 00:00:09,240 --> 00:00:11,340 So I want to discuss it just a bit. 5 00:00:12,270 --> 00:00:17,910 So a dictionary in reality is, of course, something where you can look up a word, for example, and 6 00:00:17,910 --> 00:00:24,300 here it's a bit similar to dictionaries are related to lists and arrays, but they behave a bit differently. 7 00:00:25,200 --> 00:00:29,520 So let me just show you I will define just some dictionary and call it dictionary one. 8 00:00:30,030 --> 00:00:36,750 And you start and end the dictionary with these curly brackets and to just make it look a bit better. 9 00:00:36,780 --> 00:00:38,040 Let me write it down like this. 10 00:00:38,040 --> 00:00:43,560 So the syntax here is that you have some key words. 11 00:00:44,790 --> 00:00:49,770 For example, a property and I want to make this dictionary about cars. 12 00:00:50,640 --> 00:00:54,720 So the first dictionary should be about some mercy car. 13 00:00:54,930 --> 00:00:59,310 So the first property, the first keyword that I add here is brand. 14 00:00:59,910 --> 00:01:05,099 So the brand property will have to value could be a number or could be a string. 15 00:01:05,610 --> 00:01:14,070 And here it's string Mercedes, and then we can add other keywords and other properties. 16 00:01:14,280 --> 00:01:20,190 For example, the model and here the value is again, a string. 17 00:01:20,610 --> 00:01:28,410 And let's just take some car off Mercedes, and we can, of course, add other properties like color 18 00:01:28,710 --> 00:01:29,790 or year. 19 00:01:31,530 --> 00:01:35,370 The year is, for example, this one. 20 00:01:36,450 --> 00:01:43,440 So now we have a dictionary explaining or containing properties of our car. 21 00:01:44,460 --> 00:01:52,260 So if I run this, it is defined and now I can just call again the variable or the dictionary by writing 22 00:01:52,500 --> 00:01:52,800 one. 23 00:01:53,700 --> 00:01:56,460 And you see, this is what the dictionary now looks like. 24 00:01:57,510 --> 00:01:57,780 Sort of. 25 00:01:57,780 --> 00:01:58,620 Can we do with this? 26 00:01:59,160 --> 00:02:01,590 We can select certain entries. 27 00:02:02,280 --> 00:02:11,070 So the first idea may be to just call a property or, yeah, some feature of the dictionary by using 28 00:02:11,070 --> 00:02:13,680 it in the same fashion as a list or an array. 29 00:02:13,920 --> 00:02:17,160 So maybe you would write something like this. 30 00:02:17,910 --> 00:02:22,230 This would, you may think, would call this property here. 31 00:02:23,220 --> 00:02:30,420 However, it gives us an error because it tells us there's a key error, which basically means the key 32 00:02:30,660 --> 00:02:32,880 of one does not exist here. 33 00:02:33,900 --> 00:02:36,090 So this is not working. 34 00:02:36,090 --> 00:02:39,060 So for working 35 00:02:42,690 --> 00:02:48,810 and what we have to do instead, or is the correct way of calling a property of a dictionary is to not 36 00:02:48,810 --> 00:02:51,510 add a number here, but to add the key. 37 00:02:51,750 --> 00:02:58,470 For example, we could write model, and now it gives us the value corresponding to the key called model. 38 00:02:59,340 --> 00:03:01,590 So you see, this is the main difference. 39 00:03:02,230 --> 00:03:05,640 You have not anymore a list which is numbered. 40 00:03:06,060 --> 00:03:09,540 So the order of these features here doesn't matter at all. 41 00:03:10,290 --> 00:03:15,450 You have instead, instead of writing these indices, you have to write the key words here. 42 00:03:16,020 --> 00:03:21,060 So this can be really useful if you don't want to remember the order in which you have added all of 43 00:03:21,060 --> 00:03:24,930 these properties and you want to just search for a certain value. 44 00:03:25,620 --> 00:03:31,920 So it can be quite useful to use these dictionaries, for example, when you try to build a database 45 00:03:31,920 --> 00:03:32,490 or something. 46 00:03:33,750 --> 00:03:34,770 So what else can we do? 47 00:03:35,040 --> 00:03:39,870 We can, for example, write Dictionary one dot keys. 48 00:03:41,850 --> 00:03:43,920 And this would give us all of the keys. 49 00:03:44,100 --> 00:03:54,630 So all of these words here, and likewise, we can also write a dictionary one dot values, which would 50 00:03:54,630 --> 00:03:56,070 give us then only two values. 51 00:03:56,700 --> 00:04:04,110 And you see, it is an array or, yeah, this type or in this case, it's yeah, a collection of strings 52 00:04:04,110 --> 00:04:05,670 and also of numbers. 53 00:04:07,050 --> 00:04:11,850 And then last thing that I want to show you is how can you manipulate entries in the dictionary? 54 00:04:12,330 --> 00:04:18,570 And this is quite interesting because let me show you we can write a dictionary and then we do not drive 55 00:04:18,570 --> 00:04:20,220 the index, but we write the key. 56 00:04:20,850 --> 00:04:29,070 For example, a year and now I can write the year property should be 1996, which is different to the 57 00:04:29,070 --> 00:04:31,290 1995 that we have defined earlier. 58 00:04:32,430 --> 00:04:34,980 And let me at the same time, also change another thing. 59 00:04:35,610 --> 00:04:36,570 Dictionary one. 60 00:04:36,570 --> 00:04:39,960 And this time I will use a key which I have not defined so far. 61 00:04:40,110 --> 00:04:43,590 Country and country is Germany. 62 00:04:44,430 --> 00:04:49,710 And when I run both of these commands, let us see what the dictionary now looks like. 63 00:04:52,140 --> 00:04:54,600 You see brand and model still the same. 64 00:04:54,930 --> 00:04:59,760 The here has been updated from 95 to 96 and the country. 65 00:04:59,860 --> 00:05:07,170 Property has been added completely, so it means you can use the same syntax for changing the values 66 00:05:07,170 --> 00:05:14,130 corresponding to some key steps already exist and you can add new values and new keys if the keys do 67 00:05:14,130 --> 00:05:14,910 not exist. 68 00:05:15,930 --> 00:05:21,870 So as I might, as I said, dictionaries can be quite useful, but we will probably not use them in 69 00:05:21,870 --> 00:05:22,410 the course.