1 00:00:00,210 --> 00:00:06,590 Hello, everyone, and welcome to this new and exciting session in which we are going to look at APIs. 2 00:00:06,600 --> 00:00:07,140 Now. 3 00:00:07,140 --> 00:00:10,980 API stands for Application Programming Interface. 4 00:00:11,430 --> 00:00:18,330 And in this section we're going to look at why we even need APIs and also how they work. 5 00:00:18,480 --> 00:00:27,300 Now, supposing you've just built this model right here, let's call this Model M one, and this model 6 00:00:27,300 --> 00:00:31,620 can take in an input and produce an output. 7 00:00:31,800 --> 00:00:40,710 The question is how do I make my web app like this one or my mobile app or even my desktop app access 8 00:00:40,710 --> 00:00:52,740 this model which have built such that a user of, let's say this mobile app can just by pressing a button, 9 00:00:52,740 --> 00:00:55,260 get access to this. 10 00:00:55,260 --> 00:01:02,820 My model's predictions the way we could go about this is by making use of APIs. 11 00:01:02,820 --> 00:01:12,210 That's application programming interfaces as defined here the G two dot com website and API permits 12 00:01:12,210 --> 00:01:19,140 software development and innovation to be easier by allowing programs. 13 00:01:19,140 --> 00:01:26,670 That is, for example, your web apps to communicate data and functions safely and quickly. 14 00:01:27,090 --> 00:01:33,420 APIs Does application programming interfaces accelerate innovation because more developers can build 15 00:01:33,420 --> 00:01:37,470 products based on existing data and functionality? 16 00:01:38,280 --> 00:01:40,180 Getting back to our example. 17 00:01:40,200 --> 00:01:50,820 This means that thousands of users now on the web can get access to our model and make predictions. 18 00:01:50,820 --> 00:02:01,230 Without this, developers of this web apps or mobile apps necessarily Mastering the art of model creation. 19 00:02:01,320 --> 00:02:03,540 So we can make this concepts clearer. 20 00:02:03,570 --> 00:02:05,220 Let's take this example. 21 00:02:05,220 --> 00:02:11,700 So yeah, we supposing that you get into a restaurant, you give a command to the waiter, would then 22 00:02:11,700 --> 00:02:18,620 take this command and then tells the cooks to make available the food you have in the command. 23 00:02:18,630 --> 00:02:23,310 Then once this food is ready, it sends it back to the waiter. 24 00:02:23,310 --> 00:02:24,600 That's the API. 25 00:02:24,600 --> 00:02:31,110 And then the waiter now passes on this food to you who then eats it and is happy. 26 00:02:31,140 --> 00:02:38,610 Now, in the case of computer software where we have, say, this mobile app which has to communicate 27 00:02:38,610 --> 00:02:47,280 with this API right here, then this communication has to follow certain rules or a protocol known as 28 00:02:47,280 --> 00:02:49,140 the HTTP. 29 00:02:50,130 --> 00:02:55,800 This protocol guides the way information is being transmitted via the web. 30 00:02:55,980 --> 00:03:00,990 Now, HTTP stands for Hypertext Transfer Protocol. 31 00:03:00,990 --> 00:03:04,530 So this hypertext, then transfer protocol. 32 00:03:04,950 --> 00:03:10,390 Now, the type of data exchange could be text, could be images, could be video. 33 00:03:10,390 --> 00:03:18,960 It could be any kind of data, which is understandable by both this client right here and the server. 34 00:03:19,110 --> 00:03:24,500 Also, communication following this HTTP protocol is connection less. 35 00:03:24,510 --> 00:03:32,940 That is, each time this client needs to communicate with the server to know what objects are found 36 00:03:32,940 --> 00:03:34,620 in the particular image. 37 00:03:34,620 --> 00:03:37,290 A connection is created between these two. 38 00:03:37,560 --> 00:03:43,500 Now, once the connection is created and then the client receives the output, that is the particular 39 00:03:43,500 --> 00:03:48,810 location where the objects are found in an image, that connection is closed. 40 00:03:49,470 --> 00:03:53,040 And so we we now have this which is taken off here. 41 00:03:54,090 --> 00:04:00,450 Then once we want to connect again with the API, which is found in the server, we still create or 42 00:04:00,450 --> 00:04:02,190 recreate another connection. 43 00:04:02,700 --> 00:04:09,690 Then also, as we have said, the data exchange here isn't of a particular type. 44 00:04:09,690 --> 00:04:18,450 So really this protocol doesn't force you to pass or receive a certain type of data so far as the data 45 00:04:18,480 --> 00:04:24,600 you're passing or receiving is understood by the particular entity which is sending or receiving. 46 00:04:25,590 --> 00:04:27,750 Then everything works just fine. 47 00:04:28,200 --> 00:04:33,350 Then the last property of HTTP protocol is it's actually stateless. 48 00:04:33,360 --> 00:04:38,680 That is, once you make a request and then you receive a response. 49 00:04:38,700 --> 00:04:43,650 No client information has been stored in this request response cycle. 50 00:04:44,190 --> 00:04:53,130 Hence, once data has been passed to the API and the response received, you should not expect to be 51 00:04:53,130 --> 00:04:56,800 able to retrieve this data which was being passed to the server. 52 00:04:56,820 --> 00:04:59,820 From this point we are going to go in depth into how. 53 00:05:00,410 --> 00:05:01,460 HTTP works. 54 00:05:02,180 --> 00:05:06,460 So you get to this address w w dot postman dot com. 55 00:05:06,470 --> 00:05:11,960 You could sign in or sign up in case you do not have an account with Postman. 56 00:05:11,990 --> 00:05:14,210 Now I have an account, so I'm just going to sign in. 57 00:05:14,240 --> 00:05:15,740 You get to this point here. 58 00:05:15,740 --> 00:05:19,220 You see you have workspaces, my workspace. 59 00:05:19,220 --> 00:05:24,170 And then you have this link here which comes by default. 60 00:05:24,170 --> 00:05:30,470 You have this URL, which is this information you pass in each time you want to gain access to a particular 61 00:05:30,470 --> 00:05:31,160 site. 62 00:05:31,340 --> 00:05:34,860 In this case, it's Postman Echo dot com. 63 00:05:34,880 --> 00:05:39,110 Now your URL actually stands for Uniform Resource Locator. 64 00:05:39,110 --> 00:05:50,240 And so this address right here permits us to get access to certain resources which are located somewhere 65 00:05:50,240 --> 00:05:51,650 in the web. 66 00:05:52,010 --> 00:05:55,190 And this brings us to the HTTP methods. 67 00:05:56,330 --> 00:06:00,680 If you click right here, you'll see that we have different options, like if you have you have the 68 00:06:00,680 --> 00:06:05,930 gate, you have the post, you have the port, you have the patch, and so on and so forth. 69 00:06:06,980 --> 00:06:09,440 These are known as the HTTP method. 70 00:06:10,100 --> 00:06:17,390 And each time you want to get access to a resource which is located somewhere in the web, you have 71 00:06:17,390 --> 00:06:19,440 to specify the exact method. 72 00:06:19,460 --> 00:06:26,450 So like with a gate, for example, we are saying that we want to get a resource for the post, unlike 73 00:06:26,450 --> 00:06:32,810 the get method, where our main interest is to retrieve some data. 74 00:06:33,620 --> 00:06:43,280 Here we submit an entity to the specified resource which often causes a change in status or side effects 75 00:06:43,280 --> 00:06:44,780 at the level of the server. 76 00:06:45,470 --> 00:06:52,520 So this means that we could make use of the get method when we want to retrieve a user's information 77 00:06:53,480 --> 00:07:00,290 and then we can make use of the post when we want to modify some data or add information. 78 00:07:00,290 --> 00:07:06,650 So like for example, if you want to get registered on a platform, then we make use of this post request 79 00:07:06,890 --> 00:07:10,340 as we're going to add a row on the database. 80 00:07:10,340 --> 00:07:18,500 So suppose we have this database right here where we have the user's ID, we have the user's name and 81 00:07:18,500 --> 00:07:20,690 for example, the user's password. 82 00:07:20,840 --> 00:07:30,080 So here we have this small database and then we have ID, let's say ID zero, we have the name friend 83 00:07:30,080 --> 00:07:31,430 and password. 84 00:07:31,430 --> 00:07:40,640 Let's say whatever value we have here now then we have ID one, let's say Sally, and then we have whatever 85 00:07:40,640 --> 00:07:41,570 password here. 86 00:07:41,780 --> 00:07:43,220 Then we could take two. 87 00:07:43,250 --> 00:07:51,770 We have Rita and we have whatever name we want to have here or whatever password want to have here. 88 00:07:51,770 --> 00:07:52,890 So this is it. 89 00:07:52,940 --> 00:08:00,950 Now, with the get request, we could just retrieve that Fred has an ID of zero. 90 00:08:01,010 --> 00:08:04,370 This name is Fred and the password is a given password. 91 00:08:04,370 --> 00:08:09,860 Whereas with the post request, we could add a new user. 92 00:08:09,860 --> 00:08:14,360 So that's why this pick, of course, and the change in state or side effects on the server. 93 00:08:14,360 --> 00:08:20,180 So we could actually add this new user by passing new information via this post request. 94 00:08:20,180 --> 00:08:27,620 So you could add this third and we could add say Mac, let's say Mac and that's it. 95 00:08:27,740 --> 00:08:30,290 So that's it for the post request. 96 00:08:30,320 --> 00:08:34,090 Now with the put request, we could update this data. 97 00:08:34,100 --> 00:08:42,650 So this means that here we could say we're not interested in maybe modifying the name, but if want 98 00:08:42,650 --> 00:08:47,840 to update this password, we could change this password now to some new password. 99 00:08:48,110 --> 00:08:53,470 So now we could update this row right here and the database. 100 00:08:53,480 --> 00:08:59,750 Now we could also delete, so we could just simply take this off with our delete request and that will 101 00:08:59,750 --> 00:09:02,270 be it for that row. 102 00:09:02,270 --> 00:09:09,770 We also have other methods like the head, the Connect Options, Trace and Patch, which you could check 103 00:09:09,770 --> 00:09:11,960 out in this document right here. 104 00:09:12,620 --> 00:09:17,120 But most times we make use of the get post, put and delete. 105 00:09:17,780 --> 00:09:22,190 Then also this responses have some status codes which we have seen already. 106 00:09:22,190 --> 00:09:26,840 So you maybe have seen a 200 or four. 107 00:09:26,840 --> 00:09:27,230 Okay. 108 00:09:27,230 --> 00:09:29,780 So okay, we make a request and it's okay. 109 00:09:29,780 --> 00:09:31,280 You could receive that. 110 00:09:31,280 --> 00:09:34,790 Let's, let's make this request here you are all empty. 111 00:09:34,790 --> 00:09:35,960 Let's get back here. 112 00:09:35,960 --> 00:09:37,970 And you see, you see your status. 113 00:09:37,970 --> 00:09:39,590 Let's highlight this. 114 00:09:39,590 --> 00:09:40,490 You see a status. 115 00:09:40,490 --> 00:09:41,300 Okay. 116 00:09:41,300 --> 00:09:46,490 So this as we have seen here, let's get back. 117 00:09:47,690 --> 00:09:51,710 This has, as we have seen here, HTTP response status codes. 118 00:09:51,710 --> 00:09:58,280 So you could again check in this documentation and have every detail about the different status codes. 119 00:09:58,280 --> 00:09:59,810 And you need to understand how to. 120 00:09:59,930 --> 00:10:03,290 Work with them as they're very important when you're dealing with APIs. 121 00:10:03,290 --> 00:10:09,650 So we have information, our responses, successful responses lie in between 202 99, and that's why 122 00:10:09,650 --> 00:10:11,690 you see here we have this 200. 123 00:10:13,340 --> 00:10:17,330 Status code, which is a success. 124 00:10:17,900 --> 00:10:22,750 And then we have redirections, we have client error, and we have several error. 125 00:10:22,760 --> 00:10:28,730 So if this error is coming from the person sending the API request, then you'll be between 404 and 126 00:10:28,730 --> 00:10:29,480 99. 127 00:10:29,720 --> 00:10:32,540 The errors from the server will be between 505 99. 128 00:10:32,540 --> 00:10:38,000 So when the server is down, sometimes you will see this 500 so you could check your internal server 129 00:10:38,000 --> 00:10:38,420 error. 130 00:10:38,450 --> 00:10:41,600 The server is in current situation it doesn't know how to handle. 131 00:10:41,600 --> 00:10:44,260 So you could check out all this in this documentation. 132 00:10:44,270 --> 00:10:47,750 Now let's get back here and make this error. 133 00:10:47,750 --> 00:10:50,300 So let's let's put in whatever value one year. 134 00:10:50,870 --> 00:10:56,360 Write that again and you should see your c404 not found. 135 00:10:56,360 --> 00:11:01,310 So you get your you c40 for client error. 136 00:11:01,310 --> 00:11:03,890 So this error comes from the client. 137 00:11:04,040 --> 00:11:10,880 We are going to paste this out here and then select the post request, get to the body form later. 138 00:11:10,880 --> 00:11:12,890 This is the information we'll be passing in. 139 00:11:12,890 --> 00:11:24,950 So yeah, we're going to have email teams and learn that I the password, not a password and then job 140 00:11:25,640 --> 00:11:27,920 alerts and then click on send. 141 00:11:28,400 --> 00:11:29,600 Okay, What do we get? 142 00:11:29,600 --> 00:11:31,370 You see, we have this output right here. 143 00:11:31,370 --> 00:11:36,890 We have our email, the username, the job and a token status to 100. 144 00:11:37,700 --> 00:11:42,200 Now you will notice that unlike with the get requests, we have now introduced this body data. 145 00:11:42,200 --> 00:11:47,840 So if we don't pass this body data, you see that we didn't have the right output. 146 00:11:48,110 --> 00:11:54,770 And this is because to log in to just any platform, obviously you need to pass in your credentials, 147 00:11:54,770 --> 00:11:58,250 which in this case the email, the password and the job. 148 00:11:58,790 --> 00:12:05,720 So this tells us that when doing an API call like this one, so when trying to make the client communicate 149 00:12:05,720 --> 00:12:10,100 with the server, we need to specify the HTTP method. 150 00:12:10,100 --> 00:12:12,770 We need to specify the U URL. 151 00:12:12,950 --> 00:12:17,930 Then we also need to specify the body, which in this case is all this information right here. 152 00:12:17,930 --> 00:12:22,610 That is the body information and the header information. 153 00:12:22,970 --> 00:12:29,090 Now this header and body information could be broken up into the request and response. 154 00:12:29,090 --> 00:12:34,460 So this is the request body and here is a response body. 155 00:12:35,180 --> 00:12:43,340 And then here we have the request header and the response header, which you can get by simply clicking 156 00:12:43,340 --> 00:12:44,450 on this right here. 157 00:12:44,600 --> 00:12:51,740 You can also check out a list of HTTP headers in this developer dot mozilla dot org platform right here. 158 00:12:51,890 --> 00:12:58,490 Then at the level of this response headers, take note of this content type, which is JSON. 159 00:12:58,490 --> 00:13:05,570 JSON actually stands for JavaScript object notation, which is a very easy and lightweight format for 160 00:13:05,570 --> 00:13:10,820 storing and transporting data from a client to a server and vice versa. 161 00:13:11,450 --> 00:13:20,210 The JSON format is programming language independent, and so if we have a client with code reading in 162 00:13:20,210 --> 00:13:29,480 JavaScript, it can communicate JSON data to this API via this request, which is reading, for example, 163 00:13:29,480 --> 00:13:31,880 in another programming language like Python. 164 00:13:31,880 --> 00:13:41,000 And then after processing data, the response in JSON format will still be understood by this JavaScript 165 00:13:41,000 --> 00:13:41,780 client. 166 00:13:41,810 --> 00:13:48,050 Now, to better understand the JSON formatting, let's look at this output which was generated after 167 00:13:48,050 --> 00:13:53,570 we made the get request on this Postman Echo API right here. 168 00:13:54,140 --> 00:13:58,250 You would first notice that it starts and ends with this curly braces. 169 00:13:58,250 --> 00:14:08,120 So we start like this and we end this way and then we have information stored in key value pairs. 170 00:14:08,120 --> 00:14:11,300 So we have the key and then we have the value. 171 00:14:11,300 --> 00:14:14,390 And then each key value pair is separated by a comma. 172 00:14:14,390 --> 00:14:23,930 So we have the first key here key, and then we have the colon, and then we have the value, we have 173 00:14:23,930 --> 00:14:24,800 a comma. 174 00:14:24,800 --> 00:14:25,990 And then the next lesson. 175 00:14:26,000 --> 00:14:35,210 Q One value one, and then next we have key to value two and then separated also by a comma from the 176 00:14:35,210 --> 00:14:37,060 rest and so on and so forth. 177 00:14:37,070 --> 00:14:44,060 So here you see we have this is key one here, key one, value one. 178 00:14:44,060 --> 00:14:52,850 We have the comma and then we have key to this headers, key two headers and then value to now value 179 00:14:52,850 --> 00:14:54,560 two years all this year. 180 00:14:54,560 --> 00:14:59,360 So all this data is of value to So all this. 181 00:14:59,790 --> 00:15:05,670 So our value to and then we have a comer just like yours. 182 00:15:05,670 --> 00:15:11,250 We had this comma and then after we have key three and then value three. 183 00:15:11,640 --> 00:15:18,300 Now for a particular value, we could also have some sort of dictionary. 184 00:15:18,480 --> 00:15:21,570 And so in this case, let's take all this off. 185 00:15:21,570 --> 00:15:28,470 In this case where we had this empty dictionary, this was quite simple, but here we have this dictionary 186 00:15:28,470 --> 00:15:31,730 field with its own key value pairs. 187 00:15:31,740 --> 00:15:35,280 So here we have this key and we have this value. 188 00:15:35,280 --> 00:15:40,620 And then this value is a dictionary made of its own key value pairs. 189 00:15:40,650 --> 00:15:43,650 So you have the commerce again and just like that. 190 00:15:43,650 --> 00:15:51,120 So you have the commas separating each and every key value pair and then you're you just have this string. 191 00:15:51,120 --> 00:15:57,810 So basically what we have in here is we have a key, which is a string. 192 00:15:58,620 --> 00:16:02,220 And we have a value, which is some variable. 193 00:16:02,220 --> 00:16:05,160 Now this variable can be a dictionary like this. 194 00:16:05,160 --> 00:16:11,490 The first two examples, or it can be a string, or it could be an integer or even a boolean. 195 00:16:11,760 --> 00:16:15,780 Now, if you check on this other request, here's the push request. 196 00:16:15,780 --> 00:16:18,420 You'll see this same formatting. 197 00:16:18,420 --> 00:16:23,310 So we have the curly braces which open and close, and then we have each key. 198 00:16:23,310 --> 00:16:25,530 And this value, the key is value. 199 00:16:25,560 --> 00:16:26,550 Key value. 200 00:16:26,550 --> 00:16:28,720 And finally, key value. 201 00:16:28,740 --> 00:16:30,870 Now, this was for the response. 202 00:16:30,870 --> 00:16:32,850 So this was the response body. 203 00:16:33,090 --> 00:16:38,070 Let's go ahead and check at the request body, request body. 204 00:16:38,070 --> 00:16:45,060 We had this form data, but actually we could have raw JSON data which is passed. 205 00:16:45,060 --> 00:16:53,280 So instead of using this, like basically using this UI, we could have this raw and then pass in JSON 206 00:16:53,280 --> 00:16:53,640 data. 207 00:16:53,640 --> 00:16:57,690 So it's here is actually very easy to to write this out. 208 00:16:57,840 --> 00:16:59,220 Let's have this here. 209 00:16:59,250 --> 00:17:01,560 Let's check back at the form data. 210 00:17:01,560 --> 00:17:03,720 We have email, password and job. 211 00:17:04,530 --> 00:17:08,010 Yeah, we have the same so we have email. 212 00:17:08,400 --> 00:17:09,360 There we go. 213 00:17:09,360 --> 00:17:17,970 We specify the email, learn the AI, and then we have the password. 214 00:17:18,480 --> 00:17:24,930 Our password is not a password, so not a password. 215 00:17:25,050 --> 00:17:26,040 There we go. 216 00:17:26,040 --> 00:17:27,690 Next and final one. 217 00:17:27,690 --> 00:17:29,040 We have the job. 218 00:17:29,040 --> 00:17:34,590 We have your new learns. 219 00:17:34,620 --> 00:17:35,970 Okay, so we have that. 220 00:17:35,970 --> 00:17:41,610 So notice how here we constructing this raw data, which we're going to pass in and we're going to see 221 00:17:41,610 --> 00:17:43,050 the output we get your. 222 00:17:43,050 --> 00:17:48,750 So let's send this and what do we get here is what we get as output. 223 00:17:48,750 --> 00:17:52,050 You see your unsupported major type text planning requests. 224 00:17:52,050 --> 00:17:59,100 So this means that the request we sent was text type and not the JSON format. 225 00:17:59,100 --> 00:18:03,990 So you'll notice here we have text which was selected and we just simply have to change this to JSON. 226 00:18:03,990 --> 00:18:08,130 So changing the suggestion, what do you notice is here a change in color? 227 00:18:08,130 --> 00:18:15,090 That is because this now knows that here are the keys which are in red and the values in blue takes 228 00:18:15,090 --> 00:18:18,150 it back to C turns back to all black. 229 00:18:18,180 --> 00:18:21,570 Let's get back to JSON and then rerun this. 230 00:18:21,570 --> 00:18:27,300 So we click on Sell On Send and let's see the output using pass error. 231 00:18:28,630 --> 00:18:29,940 We check that here. 232 00:18:29,970 --> 00:18:32,760 Let's take that off and then send again. 233 00:18:33,180 --> 00:18:33,590 Okay. 234 00:18:33,600 --> 00:18:38,910 So you see now that once we correct that and send this JSON data, we have this output. 235 00:18:38,910 --> 00:18:44,340 So basically using this form data right here, which you could now take off, let's take this off is 236 00:18:44,340 --> 00:18:47,660 the same as passing this raw JSON data. 237 00:18:47,670 --> 00:18:54,510 So the role of post mine is to make it easier for people to test their APIs using this kind of graphical 238 00:18:54,510 --> 00:18:55,320 user interface. 239 00:18:55,320 --> 00:19:02,970 But you could always actually do it by passing this raw JSON data, as you can see here. 240 00:19:03,600 --> 00:19:05,100 And so now you have the status. 241 00:19:05,100 --> 00:19:05,640 Okay? 242 00:19:05,640 --> 00:19:10,530 Whereas when we had this text, let's send so you could see the status, you see for one five unsupported 243 00:19:10,530 --> 00:19:15,510 media type, let's get back to JSON and send and that's what we have. 244 00:19:16,380 --> 00:19:23,220 You also notice again that the level of the headers, we have this JSON format, so the body, the output 245 00:19:23,220 --> 00:19:26,280 we have here is JSON data. 246 00:19:26,580 --> 00:19:33,090 Then instead of passing this, let's add in some random stuff here and click on send. 247 00:19:33,300 --> 00:19:34,350 What do we have? 248 00:19:34,350 --> 00:19:40,680 We have all four not found, but we'll notice that the content type that we have now is no longer the 249 00:19:40,680 --> 00:19:43,380 JSON, but instead HTML. 250 00:19:43,380 --> 00:19:48,690 And when you check out the body, you see we have this year preview page not found. 251 00:19:49,020 --> 00:19:54,960 This shows us that we can have different content types exchanged between the client and the server.