Python Json Module

JSON stands for JavaScript Object Notation and is a lightweight format for storing and transporting data. JSON is often used when data is sent from a server to a web page.

Python has the built-in module json, which allow us to work with JSON data.

import json

JSON Data Types

A JSON object is similar to a Python dictionary, but has the following differences:

• JSON Keys are always string.
• Strings are always enclosed with double quotes.
• A JSON boolean start with lowercase letters.
• null is the JSON equivalent of Python None.

The data types JSON supports are:

• String
• Number
• boolean
• null
• Object
• Array

Example:

{
  "name": "Charles",
  "age": 33,
  "has_hair": false,
  "hobbies": ["photography", "running"],
  "appearance": {
    "eyes": "brown",
    "hair_color": null
  }
}

JSON loads() method

With the json.loads method, you can parse a JSON object and transform it to a Python dictionary:

>>> import json

>>> json_person = '{"name": "Charles", "age": 33, "has_hair": false, "hobbies": ["photography", "running"]}'
>>> python_person = json.loads(json_person)
>>> python_person
# {'name': 'Charles', 'age': 33, 'has_hair': False, 'hobbies': ['photography', 'running']}

>>> type(python_person)
# <class 'dict'>

>>> python_person.get("name")
# 'Charles'

JSON dumps() method

The other way around. The dumps() method transforms a Python object to a JSON string:

>>> import json

>>> python_person = {'name': 'Charles', 'age': 33, 'has_hair': False, 'hobbies': ['photography', 'running']}
>>> json_person = json.dumps(python_person)

>>> json_person
# '{"name": "Charles", "age": 33, "has_hair": false, "hobbies": ["photography", "running"]}'

>>> type(json_person)
# <class 'str'>

Reading and writing Json Files

Reading a Json File

>>> import json
>>> with open("filename.json", "r") as f:
...     json_content = json.loads(f.read())
...
>>> json.loads(json_content)
# {'name': 'Charles', 'age': 33, 'has_hair': False}

Writing a Json File

>>> import json

>>> person = {'name': 'Charles', 'age': 33}

>>> with open("filename.json", "w") as f:
...     f.write(json.dumps(person))