1 00:00:01,170 --> 00:00:06,560 In this lecture, I'm going to show you how to use dictionaries in Python, the dictionary is a data 2 00:00:06,570 --> 00:00:13,080 structure that allows you to store key and value pairs as long as the case is neat and there's no limit 3 00:00:13,080 --> 00:00:16,170 to how many of those keys and value pairs you can store. 4 00:00:16,560 --> 00:00:19,200 Going to give you a simple example to begin with. 5 00:00:19,590 --> 00:00:25,740 So let's say that you're building an application that keeps track of the specifications of your E.S.P 6 00:00:25,740 --> 00:00:26,370 32. 7 00:00:26,850 --> 00:00:30,560 You could use a dictionary like this one here. 8 00:00:30,570 --> 00:00:40,250 There are about Paiste girl that contains information about the E.S.P 32 information about the manufacturer, 9 00:00:40,590 --> 00:00:44,310 the type of device it is that should be used using and so on. 10 00:00:44,370 --> 00:00:49,710 So as you can see, I've got multiple keys like manufacturer with. 11 00:00:50,810 --> 00:00:59,150 The value for that key, so there's another key here type and its value is microcontroller is a key 12 00:00:59,150 --> 00:01:05,060 city, you and the value your piece of string in this case, of course, you can have values that are 13 00:01:05,060 --> 00:01:07,710 numerical or a booleans, et cetera. 14 00:01:08,750 --> 00:01:19,790 If you check out the contents of this dictionary, just type in its name, you'll see that it starts 15 00:01:19,790 --> 00:01:24,800 with a curly bracket, finishes with a curly bracket, and then you've got the key and the values in 16 00:01:24,800 --> 00:01:26,030 between four. 17 00:01:26,030 --> 00:01:28,010 Click on the dictionary. 18 00:01:28,160 --> 00:01:31,170 It appears as well in the object, Inspector. 19 00:01:31,200 --> 00:01:33,950 So you can see it in a table format. 20 00:01:35,390 --> 00:01:40,520 Now you can do a few operations on a dictionary once you have it. 21 00:01:41,090 --> 00:01:48,510 For example, a common one is to use the list command and pass in the name of the dictionary. 22 00:01:48,740 --> 00:01:55,820 And what this is going to do is to bring back or give you create a list that contains the individual 23 00:01:55,820 --> 00:01:58,750 keys that are part of this dictionary. 24 00:01:59,200 --> 00:02:01,530 This you can see the square brackets. 25 00:02:01,550 --> 00:02:02,510 This is a list. 26 00:02:02,510 --> 00:02:09,980 You can use it in a iterator like a folded, for example, so that you can iterate through all of the 27 00:02:09,980 --> 00:02:18,110 keys of the dictionary and perhaps print out the values for each key or do some other kind of text processing. 28 00:02:19,440 --> 00:02:25,740 Of course, you can extract the individual values for each given key. 29 00:02:26,160 --> 00:02:37,860 So, for example, if you wanted to print out the RAND value or the value stored in the RAND key of 30 00:02:37,860 --> 00:02:44,400 the dictionary, then you can use the square brackets and then in between the square brackets, type 31 00:02:44,400 --> 00:02:48,860 in the name of the key that you want to get the value of it into. 32 00:02:48,870 --> 00:02:55,320 And you will give you that specific value, which is this one right here. 33 00:02:56,760 --> 00:03:04,680 Dictionaries are mutable, which means that you can make changes to the values of existing keys or you 34 00:03:04,680 --> 00:03:07,210 can add new key and value pairs. 35 00:03:07,620 --> 00:03:13,790 So, for example, I can make a small change to the brand that you can see here. 36 00:03:14,520 --> 00:03:21,060 I'm making reference to the particular key that I want to change the value of the material change to 37 00:03:21,060 --> 00:03:23,490 the value stored there originally. 38 00:03:24,100 --> 00:03:28,640 That's five hundred and twelve kilobytes of static ram. 39 00:03:28,650 --> 00:03:33,030 Let's make that five twenty one for the sake of the argument hit enter. 40 00:03:33,060 --> 00:03:39,840 So now we've got a new value for that Calixto against that key. 41 00:03:40,440 --> 00:03:44,310 So in other words, dictionaries are mutable. 42 00:03:44,890 --> 00:03:46,890 You can also use. 43 00:03:48,100 --> 00:03:57,760 A Syntex like this, in order to check that a particular case exists inside a dictionary so you can 44 00:03:57,760 --> 00:04:04,400 say the name of the key and check using the key word if it exists inside the dictionary. 45 00:04:04,420 --> 00:04:06,370 In this case, it does exist. 46 00:04:06,910 --> 00:04:11,920 If I search for something that does not exist, then. 47 00:04:14,850 --> 00:04:16,680 You'll get folks, it's expected. 48 00:04:17,680 --> 00:04:23,260 Now, the easiest way, as I showed you the beginning, the easiest way to create a new dictionary is 49 00:04:23,260 --> 00:04:27,390 to use the curly brackets and then the key values inside the curly brackets. 50 00:04:27,400 --> 00:04:33,790 But there's also a constructor that you can use, which can be an example here. 51 00:04:35,040 --> 00:04:43,610 Expect this to this constructor uses the dictionary with Dict Keywood, and then you've got the parentheses 52 00:04:44,180 --> 00:04:52,940 for the keyword and for the square brackets open and and then inside parentheses, you list the key 53 00:04:52,940 --> 00:04:54,320 value pairs like that. 54 00:04:55,940 --> 00:04:58,100 And that has the same result. 55 00:04:58,490 --> 00:05:06,400 Eventually, he has a new dictionary that looks like this, just like the one that we created up there 56 00:05:06,740 --> 00:05:09,920 using two different ways to achieve the same result. 57 00:05:11,060 --> 00:05:13,780 And that's how you use dictionaries completely.