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So what are the response codes that we can get from an API?
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Response codes actually have a very specific meaning,
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but the most important thing they tell us is if our request succeeded or
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if it failed. Now, if you've been using the internet for a while,
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you've probably come across the 404 response code. And the 404
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response code basically means that the thing that you're looking for doesn't
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exist. And you can see various websites having fun with this
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404 page.
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Basically when you're trying to retrieve something from a website and it doesn't
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actually have the thing you're looking for, then this is the code you get.
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But there's actually a lot more response codes other than just 404.
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And in fact,
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you could summarize these status codes just by looking at the first number.
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If it is 100 and something, then it's telling you, hold on,
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something's happening. This is not final.
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If it's 200 something then it is saying, here you go. Everything was successful.
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You should be getting the data you expected.
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If it's 300 something then it usually means you don't actually have permission
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to get this thing, so go away. 400 something, it means that
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you screwed up. Either it could be a 404
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which means that you screwed up
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and the thing you're looking for doesn't even exist,
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or it could be 500 something, which means I,
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as in the server that you are making the request to, screwed up. And maybe the
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server is down, maybe the website is down or maybe there's some other issue.
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So that's just a quick,
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at a glance, sort of way of remembering what's actually happening
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when you are getting these response codes.
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Now you can actually dig deeper into this response object and you can get a
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whole bunch of things from it. For example,
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if you wanted to know the actual status code instead of just a response object,
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then you can say response.status_code,
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and you actually only get the status code. But notice how
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if I change this URL and I make a typo in here,
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instead of iss I have is,
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then now I get a 404 as my response status code.
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OK. So if we get the status code 200 then it means that we were successful.
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But what do we do when we get a different status code?
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What should our program do when the request fails?
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We might be tempted to write code like this. By checking to see if the response
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.status_code is not equal to 200,
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we can actually figure out well, this means that there probably was an error.
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Now it doesn't really make sense to just print out an error because the user who's
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using our program might be expecting something to happen.
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So in most, cases you might want to raise an exception instead.
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You could say bad response from ISS API.
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But we learned from our module on errors and exceptions,
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this is not very good. Firstly, this is not a very specific exception.
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It's going to raise a very general type of exception. And secondly,
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all that we're catching is when the status code is not 200.
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What if we wanted you to know specifically which status code we got back? Well,
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we could, of course check well
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if the response status code was equal to say
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404, then we'll raise a particular type of exception that says that resource
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does not exist. And then we can have,
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um, an elif that says, well,
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if the response status code was 401,
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then that means that you should raise an exception because this particular code
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only happens when you are not authorized to access this data.
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Now there's a lot of status codes that you could be getting back.
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And in the course
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resources I'll link to this particular web page where it tells you all of the
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possible codes that you could be getting and what it means. As you can imagine,
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it's impossible for us to write this many
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if statements checking for every single possibility. What do we do instead?
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You can actually do away with all of this by getting the request module
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to generate the exception instead.
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The requests module is the most popular way for Python developers to work with
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APIs. And you can see in their statistics just the number of stars,
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number of forks,
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and from these stats, you can see just how much active development there is and
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how popular this particular module is. Now,
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if you want to take a look at the documentation,
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then you get taken to their website and it tells you all of the things that it
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can do, which is quite a lot actually.
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Now I won't read through all of this with you,
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but if we take a look at one of the sections, Errors and Exceptions,
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you can actually call raise for status on the response you get back in order
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to raise a HTTP error
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if the request returned an unsuccessful status code.
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Basically instead of us trying to raise an exception for every single possible
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status code and telling the developer what might be the reason, we can simply use
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the request module by saying response.raise_for_status.
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So now what you'll see is that if we don't get a 200
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which is the pass-- Let's say I mess up this end point again,
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then you'll see an exception being raised and it's telling us, look,
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it's a 404 client error. This URL is not found.
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So this request module is actually really powerful and we're going to see how to use
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various aspects of it in the upcoming lessons.
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But for now, the first thing we need to get hold of is the actual data from this
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particular API. To do that,
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we tap into our response and we get the JSON data.
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So this is the actual data. And when I print it,
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you can see that it looks exactly the same as what we got in our browser.
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Coming back to our code where we have this JSON,
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we can tap into it just like we would for any Python dictionary.
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We could use some square brackets and then type in the name of a key that we're
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interested in. For example,
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if this was a Python dictionary and we wanted to know the iss_position,
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then we would add the square brackets and then pass in iss_ position.
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And now when we print data,
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you can see it's now narrowed down and drilled into the position to give us this
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longitude and latitude.
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So we can go even further and tag on another set of square brackets and try to
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get hold of, say the longitude.
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And now we get that actual piece of data. There you have it.
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We get access to the longitude by tapping into our data in the format of a JSON
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and then getting the iss_position. And inside that dictionary,
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we can get hold of the longitude. And we can do the same thing in order to get
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hold of the latitude,
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right?
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But we would change the key of course, to latitude.
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So now I'm going to create a tuple with the longitude and the latitude.
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And now if I print it out,
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you can see how I've managed to nicely format my code and get the pieces of
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data that I want in order to be able to work with it in my project. Now,
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if you wanna see where that particular latitude and longitude is on the world
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map, then we can use a tool called latlong.net.
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So if you go to geographic tools and go to latitude and longitude to address,
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then you can paste in the longitude and latitude values that we got from
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our API. And when we click convert, then you'll see on the map,
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it shows where in the world the ISS is right now.
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So at the moment, it's somewhere to the East of Japan over the Pacific ocean.
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And of course, it's telling you no address found because I don't think anybody
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lives right there.
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So have a play around with that and make sure that you've fully understood
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what's happening in these few lines of code and how we use the API endpoint to
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get the data that we're showing up right here. In the next lesson
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I've got a challenge for you.