1 00:00:00,760 --> 00:00:02,520 - [Instructor] Hi and welcome back to the course. 2 00:00:02,520 --> 00:00:03,759 In this video, we're going to continue 3 00:00:03,759 --> 00:00:07,760 with our project, or in fact, actually start our project 4 00:00:07,760 --> 00:00:10,832 and make sure that we match the API endpoints 5 00:00:10,832 --> 00:00:13,621 that we decided in the last video. 6 00:00:13,621 --> 00:00:16,519 So, we had a couple of endpoints, 7 00:00:16,519 --> 00:00:21,153 some related to item and some related to items, 8 00:00:21,153 --> 00:00:22,329 and in this video we're going to be 9 00:00:22,329 --> 00:00:24,579 creating the item resource. 10 00:00:26,901 --> 00:00:29,759 I mentioned earlier that these resources normally 11 00:00:29,759 --> 00:00:32,200 are stored in a database. 12 00:00:32,200 --> 00:00:35,362 For this section, we're not going to use a database. 13 00:00:35,362 --> 00:00:37,452 We're going to introduce that in the next section. 14 00:00:37,452 --> 00:00:39,397 In this section, we're going to introduce 15 00:00:39,397 --> 00:00:42,588 flask restful and authentication, 16 00:00:42,588 --> 00:00:44,300 so in the next section we'll look at databases. 17 00:00:44,300 --> 00:00:47,256 For now, we're going to use an in-memory database, 18 00:00:47,256 --> 00:00:49,826 which is just a Python list, 19 00:00:49,826 --> 00:00:53,993 and I'm going to just create a sort of list called items. 20 00:00:54,930 --> 00:00:59,069 And this is going to contain a dictionary for each item, 21 00:00:59,069 --> 00:01:02,020 just as we did in the last section. 22 00:01:02,020 --> 00:01:04,853 Then I'm going to rename my resource to be item, 23 00:01:04,853 --> 00:01:06,925 just so it makes a bit more sense, 24 00:01:06,925 --> 00:01:10,063 and also remember to rename it down here as well, 25 00:01:10,063 --> 00:01:13,154 and also to rename it there. 26 00:01:13,154 --> 00:01:14,498 Now I'm going to delete this comment 27 00:01:14,498 --> 00:01:16,658 because it no longer makes sense, 28 00:01:16,658 --> 00:01:18,288 however, we're still gonna access items 29 00:01:18,288 --> 00:01:22,455 the very same way, only it's going to be /item/itemname. 30 00:01:24,077 --> 00:01:27,160 Now, we're going to need to get items 31 00:01:28,894 --> 00:01:32,077 and also to be able to create items. 32 00:01:32,077 --> 00:01:35,639 We're going to start with those two capabilities 33 00:01:35,639 --> 00:01:38,209 and we're going to add the ability to modify items 34 00:01:38,209 --> 00:01:41,448 and delete items just a bit later. 35 00:01:41,448 --> 00:01:44,907 So the get method has some code there, 36 00:01:44,907 --> 00:01:46,824 and we're gonna change that in a moment, 37 00:01:46,824 --> 00:01:48,617 and the post method has to have 38 00:01:48,617 --> 00:01:52,082 exactly the same method signature, 39 00:01:52,082 --> 00:01:55,082 that is, the same set of parameters. 40 00:01:56,539 --> 00:02:00,706 That is because when we access /item/itemname, 41 00:02:01,864 --> 00:02:05,560 that name is going to come to be name here, 42 00:02:05,560 --> 00:02:07,561 so even though this request 43 00:02:07,561 --> 00:02:09,905 is going to have a JSON payload, 44 00:02:09,905 --> 00:02:12,201 some data sent in through JSON, 45 00:02:12,201 --> 00:02:16,368 and we could send the name on that JSON file as well, 46 00:02:17,601 --> 00:02:19,396 we are not going to do that. 47 00:02:19,396 --> 00:02:21,001 We are going to instead receive it 48 00:02:21,001 --> 00:02:24,084 through the URL so all of these things can be accessed 49 00:02:24,084 --> 00:02:28,167 at the same endpoint just changing the http verb. 50 00:02:29,091 --> 00:02:32,213 That makes things just a lot easier. 51 00:02:32,213 --> 00:02:35,775 Okay, in order to create items, it's very simple. 52 00:02:35,775 --> 00:02:39,183 We're going to start without even looking at the JSON. 53 00:02:39,183 --> 00:02:44,047 We're going to start by saying item is equal to a name, 54 00:02:44,047 --> 00:02:46,662 which is the name which is a parameter, 55 00:02:46,662 --> 00:02:50,829 and a price, which I'm going to hardcode to 12, say. 56 00:02:53,086 --> 00:02:57,053 Now, how do we add this item to our items list? 57 00:02:57,053 --> 00:02:59,803 I'm sure you know how to do that. 58 00:03:03,099 --> 00:03:04,195 Hopefully you got it right. 59 00:03:04,195 --> 00:03:08,013 The way to do that is to do items.append 60 00:03:08,013 --> 00:03:09,924 and then the item there, and what that'll do, 61 00:03:09,924 --> 00:03:12,452 is that'll put this dictionary as one of the elements 62 00:03:12,452 --> 00:03:15,084 in this list at the very end of the list. 63 00:03:15,084 --> 00:03:17,171 And when we do that, again, it'll put another element 64 00:03:17,171 --> 00:03:19,004 at the end, and so on. 65 00:03:20,077 --> 00:03:23,494 Finally, we also want to tell the client, 66 00:03:24,784 --> 00:03:27,341 in this case, Postman, but it could be a mobile app 67 00:03:27,341 --> 00:03:31,976 or web app, that we have processed this addition, 68 00:03:31,976 --> 00:03:36,774 that we have created this item and added it to our database, 69 00:03:36,774 --> 00:03:38,605 in this case, our list. 70 00:03:38,605 --> 00:03:41,294 In order to do that, we're going to just return item 71 00:03:41,294 --> 00:03:45,461 so that the application knows that this has happened. 72 00:03:47,580 --> 00:03:50,848 Okay, now, I would like to test this out, 73 00:03:50,848 --> 00:03:53,663 see if it works, but unfortunately, it's not really possible 74 00:03:53,663 --> 00:03:57,183 without implementing the get method, 75 00:03:57,183 --> 00:03:59,567 so let's do that as well. 76 00:03:59,567 --> 00:04:03,852 Get is going to look in this list and retrieve an item 77 00:04:03,852 --> 00:04:07,521 that matches the name that has been requested. 78 00:04:07,521 --> 00:04:09,114 I think that with that explanation, 79 00:04:09,114 --> 00:04:11,432 you should be able to do that already. 80 00:04:11,432 --> 00:04:14,846 All it has to do is iterate over this list 81 00:04:14,846 --> 00:04:17,513 and return the appropriate item. 82 00:04:21,195 --> 00:04:22,319 I'm sure you got that. 83 00:04:22,319 --> 00:04:25,924 What to do is say for item in items: 84 00:04:25,924 --> 00:04:29,424 if item name equals the name, return item. 85 00:04:31,589 --> 00:04:34,056 Remember, item is going to be a dictionary, 86 00:04:34,056 --> 00:04:35,891 so that's just gonna get returned. 87 00:04:35,891 --> 00:04:38,129 And I forgot to mention, we'd no longer need 88 00:04:38,129 --> 00:04:41,637 to do JSONify when talking with flask restful 89 00:04:41,637 --> 00:04:43,718 because flask restful does it for us, 90 00:04:43,718 --> 00:04:46,220 so we can just return dictionaries. 91 00:04:46,220 --> 00:04:49,036 That probably evident by now, 92 00:04:49,036 --> 00:04:52,469 but nevertheless, thought I should mention that. 93 00:04:52,469 --> 00:04:56,472 Okay, so now we've got two working endpoints, 94 00:04:56,472 --> 00:04:58,471 and what we have to do is just try it out 95 00:04:58,471 --> 00:05:00,047 to make sure it works, really. 96 00:05:00,047 --> 00:05:02,846 So let's open up a terminal that we've got here 97 00:05:02,846 --> 00:05:07,013 and I am going to go and cancel that and run it again. 98 00:05:09,457 --> 00:05:13,944 Then, let's go over to, not this one, but Postman, 99 00:05:13,944 --> 00:05:16,106 and we're going to use the endpoints 100 00:05:16,106 --> 00:05:18,318 that we've already created. 101 00:05:18,318 --> 00:05:21,988 So the first thing to do is to create a new item, 102 00:05:21,988 --> 00:05:23,830 and this item has a body, 103 00:05:23,830 --> 00:05:26,349 but we're not using that in our code, and that's fine. 104 00:05:26,349 --> 00:05:29,600 Even though it has a body, we don't have to use it. 105 00:05:29,600 --> 00:05:31,400 So we're going to leave the body and the content type 106 00:05:31,400 --> 00:05:33,758 as it is, and with the knowledge 107 00:05:33,758 --> 00:05:35,931 that it's not getting used, 108 00:05:35,931 --> 00:05:39,787 and then we are going to create a chair. 109 00:05:39,787 --> 00:05:41,037 So, let's send. 110 00:05:42,445 --> 00:05:46,047 Notice that what we get back is a dictionary 111 00:05:46,047 --> 00:05:48,096 that contains the price and the name. 112 00:05:48,096 --> 00:05:49,872 The price is hardcoded to 12 113 00:05:49,872 --> 00:05:53,832 and it's coming back as an integer as opposed to a float, 114 00:05:53,832 --> 00:05:55,187 and that's fine in this case. 115 00:05:55,187 --> 00:05:57,263 It doesn't really matter. 116 00:05:57,263 --> 00:05:59,976 And the name is a chair there. 117 00:05:59,976 --> 00:06:04,105 Now, this should also have added the item, the chair, 118 00:06:04,105 --> 00:06:05,938 to our items database. 119 00:06:06,922 --> 00:06:09,839 So, let's go and retrieve the chair 120 00:06:11,830 --> 00:06:15,149 and see if that does come out. 121 00:06:15,149 --> 00:06:17,538 And as you can see, now we are getting the chair, 122 00:06:17,538 --> 00:06:21,112 and it's coming out with the price 12, as well. 123 00:06:21,112 --> 00:06:22,869 So what does this tell us? 124 00:06:22,869 --> 00:06:27,111 It tells us that what we've implemented here is correct. 125 00:06:27,111 --> 00:06:31,360 So therefore, we are able now to move forwards. 126 00:06:31,360 --> 00:06:33,922 There's a couple of things that I would like to improve 127 00:06:33,922 --> 00:06:37,749 just as a matter of making things slightly better, 128 00:06:37,749 --> 00:06:40,985 which is what happens if we don't find the item 129 00:06:40,985 --> 00:06:42,735 with a specific name. 130 00:06:44,422 --> 00:06:46,716 Well, here's what would happen right now 131 00:06:46,716 --> 00:06:49,216 if we do something like piano. 132 00:06:52,363 --> 00:06:53,726 Null. 133 00:06:53,726 --> 00:06:56,915 Now, for those of you that remember what I mentioned earlier 134 00:06:56,915 --> 00:07:01,109 about JSON always having to be a dictionary, 135 00:07:01,109 --> 00:07:03,688 this is not valid JSON. 136 00:07:03,688 --> 00:07:07,136 Postman is accepting it because Postman is really good, 137 00:07:07,136 --> 00:07:09,702 but there are many other libraries 138 00:07:09,702 --> 00:07:13,291 like Angular JS, which may not accept this. 139 00:07:13,291 --> 00:07:15,174 So, instead of returning just null, 140 00:07:15,174 --> 00:07:16,490 which is what this method returns, 141 00:07:16,490 --> 00:07:21,269 as we know, all Python methods return none by default, 142 00:07:21,269 --> 00:07:23,275 what we have to do is change that return none 143 00:07:23,275 --> 00:07:26,108 to be something like item is none. 144 00:07:28,880 --> 00:07:32,452 Now, this is essentially the same thing, but now, 145 00:07:32,452 --> 00:07:35,285 and we have to restart, of course, 146 00:07:36,752 --> 00:07:39,880 but now when we do this, we get 147 00:07:39,880 --> 00:07:43,941 a valid JSON representation of this thing. 148 00:07:43,941 --> 00:07:48,135 Another thing, the status code is 200 OK, 149 00:07:48,135 --> 00:07:50,022 but evidently things are not okay, 150 00:07:50,022 --> 00:07:52,963 because we were not able to find the item. 151 00:07:52,963 --> 00:07:55,308 So what to return in this case, 152 00:07:55,308 --> 00:07:56,697 I'm sure you know it if you remember it 153 00:07:56,697 --> 00:07:59,197 from one of the presentations. 154 00:08:01,437 --> 00:08:02,667 That's right. 155 00:08:02,667 --> 00:08:05,667 The error code for not found is 404. 156 00:08:06,616 --> 00:08:09,023 This is a common interview question as well. 157 00:08:09,023 --> 00:08:13,016 What's the most popular http status code? 158 00:08:13,016 --> 00:08:16,852 And the most popular is not 404, it is 200. 159 00:08:16,852 --> 00:08:19,840 So make sure to not fall into that trap. 160 00:08:19,840 --> 00:08:22,979 Let's restart the app, and press again, 161 00:08:22,979 --> 00:08:26,774 and now we get item is null, 404 not found. 162 00:08:26,774 --> 00:08:28,031 Awesome. 163 00:08:28,031 --> 00:08:31,151 I think our get endpoint is now working. 164 00:08:31,151 --> 00:08:34,859 Something else to remember is that creating 165 00:08:34,859 --> 00:08:38,144 also has its own http status code, 166 00:08:38,144 --> 00:08:41,561 and maybe you remember which one that is. 167 00:08:43,439 --> 00:08:44,342 Hopefully you did. 168 00:08:44,342 --> 00:08:46,686 It's very similar to 200 OK. 169 00:08:46,686 --> 00:08:50,950 200 OK is for when the server just kind of returns some data 170 00:08:50,950 --> 00:08:52,095 and says everything's okay. 171 00:08:52,095 --> 00:08:54,247 I've given you what you wanted. 172 00:08:54,247 --> 00:08:55,830 201 is for created. 173 00:08:56,684 --> 00:09:01,282 So when we go ahead and restart the app again, 174 00:09:01,282 --> 00:09:05,039 and then go back to Postman and create the chair, 175 00:09:05,039 --> 00:09:07,847 now we gat back 201 created, 176 00:09:07,847 --> 00:09:09,619 which means the object has been created 177 00:09:09,619 --> 00:09:13,097 and it has been added to the database. 178 00:09:13,097 --> 00:09:16,080 Notice there is also a very similar status code 179 00:09:16,080 --> 00:09:19,060 called 202, which is accepted, 180 00:09:19,060 --> 00:09:23,998 and the accepted code is when you are delaying the creation. 181 00:09:23,998 --> 00:09:28,985 For example, if creating the object takes a long time, 182 00:09:28,985 --> 00:09:31,835 you may say, "I'm gonna create this object, 183 00:09:31,835 --> 00:09:35,089 "return 202, and the object that's created then 184 00:09:35,089 --> 00:09:37,269 "after five or 10 minutes." 185 00:09:37,269 --> 00:09:39,974 The client doesn't have to wait five or 10 minutes, 186 00:09:39,974 --> 00:09:43,797 but it knows that you have accepted the creation of that. 187 00:09:43,797 --> 00:09:47,964 It may then fail, but that's out with the client's control. 188 00:09:49,057 --> 00:09:51,630 So, hopefully all of that makes sense. 189 00:09:51,630 --> 00:09:53,970 Using the right status codes is very important 190 00:09:53,970 --> 00:09:57,756 because it is a very quick way of clients, 191 00:09:57,756 --> 00:10:00,430 like web applications or mobile applications, 192 00:10:00,430 --> 00:10:03,518 to check whether things went wrong or not, 193 00:10:03,518 --> 00:10:04,351 and in this case, 194 00:10:04,351 --> 00:10:07,090 if we get a 404, we don't even need to check the payload 195 00:10:07,090 --> 00:10:08,638 because we know nothing's coming back 196 00:10:08,638 --> 00:10:10,960 that we're really interested in. 197 00:10:10,960 --> 00:10:13,329 If 201 comes back, then we should check the payload 198 00:10:13,329 --> 00:10:16,413 to see what has been created. 199 00:10:16,413 --> 00:10:17,818 That's everything for this video. 200 00:10:17,818 --> 00:10:18,841 In the next one, we're going to be 201 00:10:18,841 --> 00:10:20,949 implementing the item list, 202 00:10:20,949 --> 00:10:23,364 which I'm sure you can do that already, 203 00:10:23,364 --> 00:10:26,022 just with the knowledge that we've got now. 204 00:10:26,022 --> 00:10:26,855 I'll give you a hint. 205 00:10:26,855 --> 00:10:28,887 We're going to have to create a new resource 206 00:10:28,887 --> 00:10:31,852 so you can give that a go before the next video. 207 00:10:31,852 --> 00:10:33,190 I'll see you there.