1 1 00:00:01,410 --> 00:00:02,590 Welcome back, in this video, 2 2 00:00:02,590 --> 00:00:05,100 we're going to be implementing the ability to 3 3 00:00:05,100 --> 00:00:08,480 find all of the items that we have saved in our database. 4 4 00:00:08,480 --> 00:00:10,550 To do that, we're going to need to extend 5 5 00:00:10,550 --> 00:00:13,458 the capabilities of our database class. 6 6 00:00:13,458 --> 00:00:15,580 As well as inserting items, 7 7 00:00:15,580 --> 00:00:18,360 we're gonna need to be able to find items. 8 8 00:00:18,360 --> 00:00:22,030 All we have to do is say, staticmethod, 9 9 00:00:22,030 --> 00:00:23,810 that we're gonna define, and it's going to be called 10 10 00:00:23,810 --> 00:00:26,230 find, it's gonna take in a collection, which is a string, 11 11 00:00:26,230 --> 00:00:27,610 and it's gonna take in a query, 12 12 00:00:27,610 --> 00:00:29,190 which is another dictionary. 13 13 00:00:29,190 --> 00:00:31,620 This query is going to match 14 14 00:00:31,620 --> 00:00:33,920 what we're gonna search for in MongoDB. 15 15 00:00:33,920 --> 00:00:35,390 So, for example, let's say 16 16 00:00:35,390 --> 00:00:37,730 we want to search for all the items, 17 17 00:00:37,730 --> 00:00:40,150 we will just pass in an empty query. 18 18 00:00:40,150 --> 00:00:41,930 If we wanna search for items 19 19 00:00:41,930 --> 00:00:44,900 that have a specific ID property, 20 20 00:00:44,900 --> 00:00:48,130 we would pass in the ID property, like this. 21 21 00:00:48,130 --> 00:00:51,754 ID is a specific ID we wanna pass in. 22 22 00:00:51,754 --> 00:00:55,030 All right, so that's the collection and the query. 23 23 00:00:55,030 --> 00:01:00,030 And they're going to return is a pymongo.cursor, 24 24 00:01:00,550 --> 00:01:03,120 and this should be a single arrow there, 25 25 00:01:03,120 --> 00:01:05,847 cursor with a lowercase C there. 26 26 00:01:05,847 --> 00:01:09,480 The cursor in PyMongo is an iterable. 27 27 00:01:09,480 --> 00:01:11,530 It behaves very much like a list, 28 28 00:01:11,530 --> 00:01:14,823 so you can use four loops on it and that sort of stuff. 29 29 00:01:16,120 --> 00:01:17,850 So what this is gonna do is 30 30 00:01:17,850 --> 00:01:20,960 return Database.Database collection 31 31 00:01:20,960 --> 00:01:23,620 and dot find query. 32 32 00:01:23,620 --> 00:01:26,570 Nothing magical there, all we're doing is 33 33 00:01:26,570 --> 00:01:28,870 we're calling the PyMongo library, 34 34 00:01:28,870 --> 00:01:30,780 and we're saying, hey, PyMongo, 35 35 00:01:30,780 --> 00:01:34,240 find elements in this collection with this query. 36 36 00:01:34,240 --> 00:01:36,010 And if we pass in the items collection, 37 37 00:01:36,010 --> 00:01:37,550 and we pass in an empty query, 38 38 00:01:37,550 --> 00:01:39,860 it's gonna get us all the items. 39 39 00:01:39,860 --> 00:01:41,940 Now we can go back to our item model, 40 40 00:01:41,940 --> 00:01:43,660 and we can implement the method 41 41 00:01:43,660 --> 00:01:46,722 that will allow us to get all of the items from the database 42 42 00:01:46,722 --> 00:01:49,843 using that database method we just implemented. 43 43 00:01:50,710 --> 00:01:52,600 I'm going to make it a class method. 44 44 00:01:52,600 --> 00:01:54,350 You'll see why in just a moment. 45 45 00:01:54,350 --> 00:01:55,963 I'm going to call it all. 46 46 00:01:57,410 --> 00:01:59,380 This is because, in the app.py, 47 47 00:01:59,380 --> 00:02:03,270 we want to be able to do item.all, 48 48 00:02:03,270 --> 00:02:08,270 and that should give us a list of item objects. 49 49 00:02:08,910 --> 00:02:13,460 In here, we're going to get all the items from the database. 50 50 00:02:13,460 --> 00:02:17,470 I'm gonna create a variable called items from db, 51 51 00:02:17,470 --> 00:02:20,170 and then, this is gonna be equal to Database.find 52 52 00:02:21,230 --> 00:02:24,430 in the items collection, all of them. 53 53 00:02:24,430 --> 00:02:26,450 And that is the empty query that is needed 54 54 00:02:26,450 --> 00:02:28,840 to find all of the items. 55 55 00:02:28,840 --> 00:02:32,770 So what we have now is a PyMongo cursor. 56 56 00:02:32,770 --> 00:02:37,340 That is very similar to a list of Python dictionaries, 57 57 00:02:37,340 --> 00:02:40,280 where each dictionary has the information present 58 58 00:02:40,280 --> 00:02:41,583 in the items collection. 59 59 00:02:42,500 --> 00:02:46,050 So each of the dictionaries in the database 60 60 00:02:46,050 --> 00:02:49,080 has an underscore ID, a URL, 61 61 00:02:49,080 --> 00:02:51,770 a tag name, and a query. 62 62 00:02:51,770 --> 00:02:54,750 And if you remember, these are exactly the same 63 63 00:02:54,750 --> 00:02:56,877 as we have in our init method, 64 64 00:02:56,877 --> 00:03:01,223 the URL, the tag name, the query, and the underscore ID. 65 65 00:03:02,060 --> 00:03:04,000 So what are we gonna do? 66 66 00:03:04,000 --> 00:03:07,230 Instead of returning items from db, 67 67 00:03:07,230 --> 00:03:10,310 which would give us back, essentially, 68 68 00:03:10,310 --> 00:03:13,090 a list of dictionaries, what we're going to do is 69 69 00:03:13,090 --> 00:03:18,090 we're going to return a cls of item 70 70 00:03:18,570 --> 00:03:21,823 for item in items from db. 71 71 00:03:22,860 --> 00:03:27,440 What this does is it iterates over items from db, 72 72 00:03:27,440 --> 00:03:32,340 so the item is each of the dictionaries in that cursor. 73 73 00:03:32,340 --> 00:03:37,100 For each dictionary, we create a new item object 74 74 00:03:37,100 --> 00:03:39,760 using the cls notation. 75 75 00:03:39,760 --> 00:03:43,670 Cls in a class method is the current class, 76 76 00:03:43,670 --> 00:03:46,323 so this is the same as doing item. 77 77 00:03:47,165 --> 00:03:51,280 And when you pass in the double-asterisk item 78 78 00:03:51,280 --> 00:03:54,110 to the constructor, what it's saying is, 79 79 00:03:54,110 --> 00:03:57,440 pass in four arguments. 80 80 00:03:57,440 --> 00:04:00,090 ID should be equal to the ID property 81 81 00:04:00,090 --> 00:04:01,730 that's coming in from the database, 82 82 00:04:01,730 --> 00:04:03,590 the URL should be equal to URL property 83 83 00:04:03,590 --> 00:04:04,860 that's coming in from the database, 84 84 00:04:04,860 --> 00:04:07,410 and so on for the four of them. 85 85 00:04:07,410 --> 00:04:09,500 So when you do this, really, what you're doing is 86 86 00:04:09,500 --> 00:04:14,500 you're saying underscore ID equal item underscore ID, 87 87 00:04:14,801 --> 00:04:19,801 URL equal item URL, and so on for each of the properties. 88 88 00:04:20,550 --> 00:04:23,662 But because the parameters in the init method 89 89 00:04:23,662 --> 00:04:27,980 have the same name as the keys 90 90 00:04:27,980 --> 00:04:30,400 in the dictionary that we've saved, 91 91 00:04:30,400 --> 00:04:34,740 we can just do double-asterisk item. 92 92 00:04:34,740 --> 00:04:36,460 And what this is gonna give us is now, 93 93 00:04:36,460 --> 00:04:39,580 instead of a list of dictionaries, 94 94 00:04:39,580 --> 00:04:41,523 or rather, a cursor of dictionaries, 95 95 00:04:41,523 --> 00:04:45,340 it's going to give us a list of item objects. 96 96 00:04:45,340 --> 00:04:47,210 So why is that useful? 97 97 00:04:47,210 --> 00:04:51,410 Well, because now that we have a list of item objects, 98 98 00:04:51,410 --> 00:04:55,870 we can load the price of one of them. 99 99 00:04:55,870 --> 00:04:58,710 Now, we have access to this method. 100 100 00:04:58,710 --> 00:05:01,410 If this was a list of dictionaries, 101 101 00:05:01,410 --> 00:05:04,100 obviously, you wouldn't have the method on a dictionary. 102 102 00:05:04,100 --> 00:05:07,060 You would have to create the item on the check first. 103 103 00:05:07,060 --> 00:05:09,240 This method is only available on item objects, 104 104 00:05:09,240 --> 00:05:10,960 and not on dictionaries. 105 105 00:05:10,960 --> 00:05:13,690 So now that we have this, we can run the app, 106 106 00:05:13,690 --> 00:05:18,690 and as you can see, we get first the printed list of items, 107 107 00:05:20,340 --> 00:05:22,630 and this means that I have two items 108 108 00:05:22,630 --> 00:05:24,090 at the moment in my database. 109 109 00:05:24,090 --> 00:05:25,930 They are same, they have the same URL, 110 110 00:05:25,930 --> 00:05:28,590 that's because I've saved it twice from the app twice. 111 111 00:05:28,590 --> 00:05:29,707 And then, we're gonna get the first one, 112 112 00:05:29,707 --> 00:05:31,760 and we're gonna load the price of it, 113 113 00:05:31,760 --> 00:05:34,113 and that's 1469.0. 114 114 00:05:35,830 --> 00:05:37,890 So what have we done here? 115 115 00:05:37,890 --> 00:05:42,890 We first decided how we wanted to interact with our item. 116 116 00:05:43,520 --> 00:05:46,030 We wanted to be able to do item dot all 117 117 00:05:46,030 --> 00:05:47,270 to retrieve all the items 118 118 00:05:47,270 --> 00:05:51,210 because I feel that this is a pretty straightforward way of 119 119 00:05:51,210 --> 00:05:52,943 interacting with the database. 120 120 00:05:53,900 --> 00:05:57,030 Then, we wanted to be able to call the methods 121 121 00:05:57,030 --> 00:06:00,080 on each of the elements that this returns, 122 122 00:06:00,080 --> 00:06:04,240 which means this has to return a list of item objects. 123 123 00:06:04,240 --> 00:06:07,400 So then, we went and implemented that. 124 124 00:06:07,400 --> 00:06:08,630 And then I implemented this thing 125 125 00:06:08,630 --> 00:06:11,380 that allows us to retrieve everything from the database 126 126 00:06:11,380 --> 00:06:14,250 and gives us an item object for each. 127 127 00:06:14,250 --> 00:06:15,340 And as part of doing that, 128 128 00:06:15,340 --> 00:06:18,480 we also had to implement this find method 129 129 00:06:18,480 --> 00:06:21,150 in the database class, which just goes to the database 130 130 00:06:21,150 --> 00:06:22,973 and finds stuff and returns it. 131 131 00:06:24,350 --> 00:06:26,560 So I hope this was useful, I hope you learned something. 132 132 00:06:26,560 --> 00:06:28,110 I'll see you on the next video.