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JSON
6:33JSON is quickly becoming the de facto standard for Web-based communication. Most APIs expect, accept, and return JSON and many pieces of desktop software use JSON for configuration files. Let's see how to use Python's built-in `json` module to read and write this handy format.
CSVs were and still are a very
popular format for importing and
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exporting data to and
from databases and spreadsheets.
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Much of the web though,
runs on another common and
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popular format, JSON, or
JavaScript Object Notation.
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No, I'm not trying to get
you to write JavaScript,
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Python's JSON module is very handy for
encoding and decoding data from JSON.
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You'll use this when you're
receiving information in your API or
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sending information to an API, or
maybe you just want to use it to read and
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write files on your server.
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JSON is pretty common for
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configuration files too,
regardless of how you're going to use it,
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it's a great format to know about, and
a great library to know how to use.
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Python's JSON library is pretty solid and
I think, pretty easy to use.
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Let's check out this JSON
file about a piece of art
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that I downloaded from
the Minneapolis Institute of Art.
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You can see that a lot of stuff in here,
I can read it like it's a dictionary and
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go, it's dated 1899, cool,
but I don't wanna do that.
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I wanna be able to do this in Python,
right?
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So I'm gonna make a new file and
I'm gonna call this art.py,
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and inside of here, first things first.
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We need to import the JSON module, so
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the JSON module has all of
our handy dandy stuff in it.
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So I'm going to open it up, what is this?
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148.json as art file.
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So I'm gonna open that up and
I'm gonna say art = jason.load(artfile),
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and then I'm gonna
print(art['description']).
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All right, cool?
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So let's go run this.
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And I get that it's a boat with two masts
in front of a bridge with a lift-gate,
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two row boats in water at left,
buildings at left, trees at right,
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that's the description I
got from the JSON file.
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Now that might not look like much but it's
really handy if you're dealing with tons
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of input from an outside source, or
lots and lots and lots of files.
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And you don't have to try and
turn plain-text files in Python Objects or
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anything like that through RegX or
some sort of, I don't even know,
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some sort of arcane incantation.
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The load method, which we used right here,
takes a file-like object and
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tries to turn that into
a Python object of some kind.
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In this case, because what we have here is
what we would call a dictionary in Python,
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it just creates a dictionary,
it creates an actual Python dictionary.
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If we had a list, an array for
JavaScript, then we would get a list
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in Python, another way that we can
do this is with the load s method.
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You'll probably hear people call
it loads instead of load s or
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load string, I call it loads all the time.
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Honestly, that's fine, that's what the
word is, but the way that it's spelled,
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what it is, is it's the way that we can
take a string with embedded JSON in it and
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turn that into a Python object.
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Let's try that out,
let's try it out down here in the shell.
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We'll do Python, import json and
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let's do nums = json.loads and
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then a string of 1,2, and 3.
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All right, and so
now if I do nums[2] I get the number 3,
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so we loaded the string in the JSON.
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In that string there was an array of
integers which the JSON module turned
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into a list of ints and
I think that's pretty handy.
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The opposite of load and
loads are the dump and
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dumps methods, so let's try them out.
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So we can do json.dumps([5, 4, 3, 2, 1]).
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No quote marks, and now, I get a string
which has the array of numbers in it,
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so it's kinda like I turned
the list into a string,
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I mean, it almost seems like I get
to str and then the list, right?
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And I could on something this simple,
but on something that's a little bit
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more complicated, you obviously
can't do that, let's try this.
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I'm gonna make myself into a dictionary,
so first_name is Kenenth,
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last_name is Love, and
my topic here at Treehouse Is Python.
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All right, so I can't just do str(me),
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I mean, I can but I don't get
exactly the right thing, right?
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So let's do json.dumps(me) and
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while it looks the same,
there is a difference because in JSON
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you have to have double quotes instead
of single quotes to make it valid.
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So this is valid JSON, what I did
before is not, and if I was to have
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numbers like that in there, we'd want
to change how those things worked.
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We could also easily send this string out
across the internet with no problems, so
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that's great,
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that's super handy, we could do something
similarly using the Dump method.
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But Dump goes directly into a file-like
object instead of into a string,
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so we have me, let's make Craig.
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So again, do first_name as Craig,
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last_name as Dennis, and
topic as Java all right?
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So we have me, and we have Craig,
and let's do with open
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teachers.json, and a for append,
although it doesn't really matter,
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cuz we're writing into this for
the first time, as teacherfile.
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Then we wanna say json.dump, and
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we're gonna dump an array of me and
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craig into teacherfile, all right?
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Let that run and now,
let's shrink that down, refresh this,
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if we checked out teachers.json
that the file that we just created.
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There's me, and
I misspelled my own name, and
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there's Craig, and
it made a list of objects.
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So that's pretty cool, that's super
awesome, the JSON module is amazingly
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handy for both encoding and decoding
data to and from files and strings.
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I find myself using it a lot with
various APIs on the web, and
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I bet that you will find it the same.
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