An Enthusiastic Programmer

Python JSON Example


JSON (JavaScript Object Notation) is a lightweight data-interchange format. Python builds very powerful build-in functionality support JSON. This article will discuss the encoding and decoding of JSON in Python. make sure you have already known JSON syntax before starting if you aren’t, please check it first.

Python support JSON Natively!

Python has a build-in package json for encoding and decoding JSON data. just throw the below little guy up to your file in the first line.

import json

Decoding JSON

json library package provides two methods for deserializing from a string(json format) to a Python Object.

json.loads(str) #Decode the json string
json.load(fileobj) #Decode while JSON file read

load() accepted a file_object parameter, deserializing from a file contents. however loads() accepted string parameter, deserializing from a string.

if the string data or the file contents being deserialized is not a valid JSON document, then a JSONDecodeError will be raised.

import json

# some JSON:
x =  '{ "school":"oxford","type":"university","location":"England"}'

# parse x:
y = json.loads(x)

# the result y is a Python dictionary:
res = y["school"] + " is a "+y["type"]+" in "+y["location"]

# Output: oxford is a university in England

Encoding JSON

json package also provides two methods for serializing Python Object as a JSON formatted string. they are:

json.dumps() #encoding to JSON objects
json.dump() #encoded string writing on file

the dump() method will write the encoded string into a file. dumps() method produces only a JSON form string.

They both accept a default parameter that should be a function that gets called for objects that can’t otherwise be serialized. it should return a JSON encoded version of the object or raise TypeError.

TypeError will be raised, if not specified the default parameter while meeting unable to handled types.

import json

# a Python object (dict):
x = {
    "name":"Jay gatsby",
    "friends":"nick carraway",

# convert into JSON:
# the result y is a JSON string:
y = json.dumps(x)

# Output: {"name": "Jay gatsby", "gender": "male", "career": ["thief", "gambler", "bootlegger"], "beloved": "daisy", "friends": "nick carraway", "great": "yes"}

you have already know how to deserializing and serializing till here. in the next chapter, we will discuss the variable conversion table between JSON and Python.

Conversion table

JSON to Python

JSON Python
Object dict
Array list
String unicode
number – int number - int, long
number – real float
True True
False False
Null None

you should make sure JSON string is valid JSON form when converting a JSON string into python. the website can help you jsonviwer.

Python to JSON

Python JSON
dict Object
list Array
unicode String
number - int, long number – int
float number – real
True True
False False
None Null

when you convert Python into JSON form string, you should also guarantee that it’s a valid python datatype that can be converted into JSON form. you should specify default parameter as a function that for custom conversion if you are not using above datatype sheet when converting.


Now everything is very clear. I will summarize steps once more.

  • import json package
  • deserializing use loads()/load()
  • serializing use dumps()/dump()
  • make all of the data that converting is valid

if you have some recommendations or thoughts, don’t stingy your words. write it in the comment area we will discuss it together.