Consuming HTTP Services in Python Transcripts
Chapter: Reading JSON data with requests
Lecture: Demo: JSON from Python

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0:00 So here I have a little bit of Json text. So, this Json string,
0:06 if converted to Json or to other objects has a demo field
0:10 and that says processing Json in Python,
0:13 and the instructor is Michael and the duration is 5, presumably minutes.
0:17 So let's start working with this, let me just print this thing out for a second,
0:22 now, notice this is still running the old one so I am going to right click
0:25 and run that and it prints it out and it's kind of indistinguishable
0:28 from say like a python dictionary,
0:31 which actually means working with Json from python is super natural
0:34 because the mapping between Json as something in Javascript or text
0:38 mapped over to Python as dictionaries is nearly one to one,
0:42 it's not exactly but very close, but let's just make sure that that is actually a string
0:47 so I'll say what is the type of this things as well, now you could see,
0:50 okay it is a str, it is, so how do we load this?
0:54 Well, Python comes with what is described as 'batteries included'
0:59 and that means it has a rich standard library including support for Json,
1:03 you could see that is coming straight out of the library,
1:06 so we don't need anything external,
1:08 we don't need to pip install anything, to work with this,
1:11 so what we are going to do is we are going to come over here
1:13 and we are going to parse this Json so we'll say data,
1:17 so there is a couple of things we can do, we can load or we can load s,
1:23 now, I think the naming choices here were super poor
1:28 how about load from string, or load from file, or something to that effect,
1:31 but load you can see fp for file pointer and load s, s for string
1:36 so much for good variable naming, but the one we are looking for
1:40 is we have some text in memory, we want to turn that from text in the form of Json
1:44 into Python dictionaries in the form of data,
1:47 so we are going to use this and this is the one you are going to use most of the time
1:50 when you are doing services because you will make an http request
1:53 and you will have text in memory, so text Json and then we can print this out again,
1:57 we'll just print out data and if I run this, you could see it looks really similar,
2:00 it's different it has single quotes instead of double,
2:03 because that is the way Python dictionaries represent themself,
2:06 and it's all in one line, again, because of that.
2:09 But if I gave you that string there, you couldn't really be sure
2:13 that that didn't come from some sort of service,
2:15 so let's go and do type again, here we go, str says it's string, now it's a dictionary
2:23 and you can see that actually the duration is a number,
2:26 it doesn't have quotes on it, and that is pretty cool,
2:28 let's get a few pieces of information here,
2:31 we'll say in structure= now we want to get information,
2:34 we want to get something on this dictionary, so that is standard Python,
2:37 you just do that by indexing in with the key so we'll say instructor
2:41 and then I'll print your instructor is { }.format, maybe I'll even spell it right,
2:50 how about that? Now if we run it, you can see your instructor is Michael,
2:53 now this is usually good, but sometimes this isn't so good,
2:56 so for example if this doesn't appear we are going to get something super bad,
3:01 we are going to get a KeyError, right, it sort of interspersed throughout here
3:05 but somewhere in here, there we go, KeyError instructor,
3:08 so we can use a different format, different style of getting the value,
3:11 so that is probably recommended because the internet you never know,
3:14 we can say get me an instructor like this and then it just says
3:15 oh, your instructor is none, or we can even ply
3:19 a default here saying substitute if there is not instructor
3:24 presented or we are just going hey look, you are getting a substitute teacher.
3:28 Alright, right now it's substitute, so if I go and put that back,
3:30 now, hey your instructor is Michael, very cool, okay, so that is great,
3:34 final thing let's make a change to this data, let's say you know what,
3:38 your new instructor is going to be Jeff, and somehow I want to
3:43 let's go and just print out the data and see that is changed,
3:48 oops, don't need that twice, do we, we have your instructor is Jeff, okay,
3:52 so here we are processing this, instructor Jeff,
3:55 but this is actually a Python dictionary, right, it's a dict,
3:59 we want this back serialized as Json, so how do we get this back,
4:03 we'll say new Json and then we have a reverse of load s to dump s,
4:10 again, naming is really kind of unfortunate but it is what it is,
4:14 you can dump Json to a file pointer, or you can dump s into memory
4:18 for the same reason that we frequently use the load s in services,
4:21 we are going to use dump s in services as well,
4:24 and then let's just print out both the type of new Json and also new Json itself.
4:28 Let her run, boom, there it is at the end we have class str and now this is the Json,
4:34 notice the double quotes and our class is still called the same
4:38 but our instructor is Jeff, same duration.
4:42 So that is basically it, working with Json from Python,
4:45 really it comes down to the Json module, load s, dump s,
4:49 and then somewhere in the middle, just working with straight up Python dictionaries,
4:54 one thing that may become some sort of hangup for you
4:58 and there are ways to work around it,
5:02 with the Json module is that is there was some kind of date in here,
5:06 this would not work so for example, if we come over here,
5:09 and this has a datetime like now,
5:15 and we'll just put str time or something like that,
5:19 if we try to run that, it's woow, datetime is not a serializable,
5:23 so basically, you can register handlers for serialization
5:26 and you could also just do like a string representation,
5:31 so you could choose like what string or representation you want,
5:33 and then we'll store it like that, okay.
5:36 But dates themselves are not supported in Json, just be careful of that.
5:40 Alright, now you know about Json and working with it from Python,
5:44 let's go get it from somewhere way more interesting than an in memory static string,
5:48 let's go get it from a web service, somewhere like gihub.