1 1 00:00:01,680 --> 00:00:03,540 In this video, we're going to be dealing with 2 2 00:00:03,540 --> 00:00:04,900 databases in our code. 3 3 00:00:04,900 --> 00:00:07,813 We're going to be saving and retrieving our items 4 4 00:00:07,813 --> 00:00:09,760 from our database. 5 5 00:00:09,760 --> 00:00:14,760 What we want to be able to do is to get this item 6 6 00:00:14,960 --> 00:00:16,650 and save it to the database. 7 7 00:00:16,650 --> 00:00:19,665 We're gonna do something like save_to_mongo, 8 8 00:00:19,665 --> 00:00:20,990 and that's gonna save it to our database 9 9 00:00:20,990 --> 00:00:23,020 and store it there. 10 10 00:00:23,020 --> 00:00:25,210 Then we wanna be able to retrieve them, 11 11 00:00:25,210 --> 00:00:26,550 so we're gonna say items_loaded. 12 12 00:00:26,550 --> 00:00:28,583 It's gonna be Item.all. 13 13 00:00:29,580 --> 00:00:32,160 Then we're gonna be able to print them out 14 14 00:00:32,160 --> 00:00:34,963 or print the price of one. 15 15 00:00:35,940 --> 00:00:38,670 Items_loaded[0].load_price. 16 16 00:00:38,670 --> 00:00:40,510 This is what we want to be able to do, 17 17 00:00:40,510 --> 00:00:42,510 but of course we can't do it just now 18 18 00:00:42,510 --> 00:00:45,500 because we don't have the save_to_mongo method 19 19 00:00:45,500 --> 00:00:48,343 and we also don't have an all class method. 20 20 00:00:49,210 --> 00:00:51,840 Do note that we're calling this all method on 21 21 00:00:51,840 --> 00:00:54,840 the item and not on the item object, 22 22 00:00:54,840 --> 00:00:57,120 so this is the item class. 23 23 00:00:57,120 --> 00:01:00,680 In order to avoid confusion, I'm going to rename 24 24 00:01:00,680 --> 00:01:03,730 this item to something like iPad 25 25 00:01:03,730 --> 00:01:05,690 because that's what it is. 26 26 00:01:05,690 --> 00:01:08,330 So I've now renamed it. 27 27 00:01:08,330 --> 00:01:09,580 Says there's a typo there. 28 28 00:01:09,580 --> 00:01:11,550 There's no typo there, PyCharm. 29 29 00:01:11,550 --> 00:01:13,690 We've got this iPad object 30 30 00:01:13,690 --> 00:01:17,110 and the all method is being called on the item class. 31 31 00:01:17,110 --> 00:01:19,960 That's just to remove some confusion there. 32 32 00:01:19,960 --> 00:01:24,960 We have to go ahead and create our methods. 33 33 00:01:25,170 --> 00:01:27,190 Let's go ahead into our item model 34 34 00:01:27,190 --> 00:01:29,483 and we're going to make some changes here. 35 35 00:01:31,030 --> 00:01:32,890 The first thing we're going to need in order to 36 36 00:01:32,890 --> 00:01:36,930 interact with MongoDB is to know what collection 37 37 00:01:36,930 --> 00:01:40,610 the objects of this type are going to go into. 38 38 00:01:40,610 --> 00:01:43,560 If you remember, a collection in MongoDB is like 39 39 00:01:43,560 --> 00:01:46,920 a table in traditional databases to some extent. 40 40 00:01:46,920 --> 00:01:49,470 You can put anything you want in it 41 41 00:01:49,470 --> 00:01:52,060 and all of the things inside the collection 42 42 00:01:52,060 --> 00:01:55,300 should be similar in some way. 43 43 00:01:55,300 --> 00:01:57,540 What we're going to do in our app is 44 44 00:01:57,540 --> 00:01:59,970 we're going to put all our items inside 45 45 00:01:59,970 --> 00:02:02,820 a collection that we're gonna call items. 46 46 00:02:02,820 --> 00:02:07,193 So we're gonna do self.collection is items. 47 47 00:02:08,320 --> 00:02:11,610 That defines the collection to be items 48 48 00:02:11,610 --> 00:02:14,323 for all objects of the class item. 49 49 00:02:16,056 --> 00:02:19,910 As part of this, we're also going to add a repr method. 50 50 00:02:19,910 --> 00:02:23,930 What this does is, when you print an item object, 51 51 00:02:23,930 --> 00:02:25,380 you're gonna be able to see this 52 52 00:02:25,380 --> 00:02:28,320 string that this returns instead of 53 53 00:02:28,320 --> 00:02:31,093 the default string representation. 54 54 00:02:32,410 --> 00:02:36,963 We're gonna say something like Item self.url. 55 55 00:02:39,300 --> 00:02:40,920 Couple of things to note here; 56 56 00:02:40,920 --> 00:02:44,250 the F in front of the quotation marks means 57 57 00:02:44,250 --> 00:02:48,040 this is an F-string, also a new thing in Python 3.6. 58 58 00:02:48,040 --> 00:02:51,070 What it allows us to do is to put a variable name 59 59 00:02:51,070 --> 00:02:53,590 inside curly braces within the string, 60 60 00:02:53,590 --> 00:02:55,450 and what happens is that the value of 61 61 00:02:55,450 --> 00:02:57,530 the variable gets placed in here 62 62 00:02:57,530 --> 00:02:59,543 instead of these curly braces. 63 63 00:03:00,800 --> 00:03:05,620 It'll print opening crocodile clip, Item, 64 64 00:03:05,620 --> 00:03:06,900 the URL of the item, 65 65 00:03:06,900 --> 00:03:08,660 and then a closing crocodile clip. 66 66 00:03:08,660 --> 00:03:10,580 The crocodile clips are my addition. 67 67 00:03:10,580 --> 00:03:12,510 You don't have to put them in if you don't want, 68 68 00:03:12,510 --> 00:03:14,860 but you do need the F in front. 69 69 00:03:14,860 --> 00:03:16,510 Optionally, instead of using an F-string, 70 70 00:03:16,510 --> 00:03:18,763 you can use a format method if you prefer. 71 71 00:03:20,698 --> 00:03:24,153 So we have this, and we also need a _id, 72 72 00:03:26,520 --> 00:03:30,280 which is going to be stored in MongoDB. 73 73 00:03:30,280 --> 00:03:34,870 This is going to be uuid.uuid4().hex. 74 74 00:03:34,870 --> 00:03:37,230 Of course we do have to import UUID. 75 75 00:03:38,800 --> 00:03:40,360 What this is going to do is it's going to 76 76 00:03:40,360 --> 00:03:43,430 generate a unique string and place it 77 77 00:03:43,430 --> 00:03:45,310 inside this property. 78 78 00:03:45,310 --> 00:03:46,950 The reason for that is because then 79 79 00:03:46,950 --> 00:03:48,760 we're going to put that into MongoDB 80 80 00:03:48,760 --> 00:03:51,950 so that we can identify each item uniquely 81 81 00:03:51,950 --> 00:03:53,280 should we have to. 82 82 00:03:53,280 --> 00:03:54,400 At the moment we don't have to, 83 83 00:03:54,400 --> 00:03:56,523 but it's a good idea to put this in there. 84 84 00:03:58,450 --> 00:04:01,750 As well as the load_price method that 85 85 00:04:01,750 --> 00:04:03,900 we've got here, we're also going to need 86 86 00:04:03,900 --> 00:04:08,240 a method that turns the item from a Python object 87 87 00:04:08,240 --> 00:04:11,200 into something that can be stored in MongoDB, 88 88 00:04:11,200 --> 00:04:14,210 and that is a Python dictionary. 89 89 00:04:14,210 --> 00:04:16,233 We're gonna have a JSON method. 90 90 00:04:17,210 --> 00:04:19,060 This is going to return a dictionary, 91 91 00:04:20,070 --> 00:04:22,940 so we might as well tell Python that it's 92 92 00:04:22,940 --> 00:04:27,880 gonna return a dictionary, like that. 93 93 00:04:27,880 --> 00:04:30,510 What it's gonna say is _id is gonna be 94 94 00:04:30,510 --> 00:04:34,513 self._id, URL is gonna be self.url, 95 95 00:04:35,760 --> 00:04:37,427 tag_name, and query. 96 96 00:04:42,500 --> 00:04:43,870 That's everything we're going to store 97 97 00:04:43,870 --> 00:04:45,300 in MongoDB for now. 98 98 00:04:45,300 --> 00:04:47,060 This may change later on as we 99 99 00:04:47,060 --> 00:04:49,070 progress through the course. 100 100 00:04:49,070 --> 00:04:51,090 One more thing that we wanna change in here 101 101 00:04:51,090 --> 00:04:54,380 is that when we are loading an item from 102 102 00:04:54,380 --> 00:04:57,760 the database, we are going to extract from 103 103 00:04:57,760 --> 00:04:59,740 the database all of these properties, 104 104 00:04:59,740 --> 00:05:02,550 ID, URL, tag name, and query, 105 105 00:05:02,550 --> 00:05:05,120 and we're going to pass all of those to 106 106 00:05:05,120 --> 00:05:07,620 the item constructor so that we can create 107 107 00:05:07,620 --> 00:05:09,990 a new item object whose properties 108 108 00:05:09,990 --> 00:05:13,410 match exactly those that are in the database. 109 109 00:05:13,410 --> 00:05:16,000 However, at the moment, we're always generating 110 110 00:05:16,000 --> 00:05:19,240 a new UUID and we're never using anything that's 111 111 00:05:19,240 --> 00:05:21,430 being passed in to the constructor. 112 112 00:05:21,430 --> 00:05:24,530 So we're gonna change that by passing in 113 113 00:05:24,530 --> 00:05:26,780 a string constructor here that is going to 114 114 00:05:26,780 --> 00:05:28,273 default to None. 115 115 00:05:29,160 --> 00:05:34,160 What we're gonna do is, if this is not None, 116 116 00:05:35,280 --> 00:05:37,520 then we're going to use that value. 117 117 00:05:37,520 --> 00:05:39,900 If it is None, then we're going to 118 118 00:05:39,900 --> 00:05:40,990 generate a new one. 119 119 00:05:40,990 --> 00:05:43,130 This is a Python shorthand that says 120 120 00:05:43,130 --> 00:05:44,950 use this value if it exists, 121 121 00:05:44,950 --> 00:05:46,543 otherwise use this one. 122 122 00:05:47,880 --> 00:05:50,884 So that's a pretty handy way of doing things. 123 123 00:05:50,884 --> 00:05:53,670 That's all the changes to our item model. 124 124 00:05:53,670 --> 00:05:57,570 We are ready to go ahead and save to MongoDB. 125 125 00:05:57,570 --> 00:06:01,090 We can actually make the change that will 126 126 00:06:01,090 --> 00:06:03,930 allow us to put this data that's coming from 127 127 00:06:03,930 --> 00:06:06,903 this JSON method into MongoDB. 128 128 00:06:08,090 --> 00:06:10,830 But before we do that, we do have to go ahead 129 129 00:06:10,830 --> 00:06:14,660 and create a way of interacting with MongoDB. 130 130 00:06:14,660 --> 00:06:16,300 We're gonna do that in the next video by 131 131 00:06:16,300 --> 00:06:19,050 going for the first time into our common package 132 132 00:06:19,050 --> 00:06:21,620 and create a database module there. 133 133 00:06:21,620 --> 00:06:22,813 I'll see you soon.