chapter-8.5-json.md

Chapter 8.5 The json module

Table of Contents:

• Chapter 8.5 The json module
  • introduction to JSON
  • JSON Data Types and its python equivalent
  • JSON basic Example
  • JSON example with nested objects
  • Dumping Python dictionary into a json string or a file
    • Dumping the dictionary into JSON string
    • Dumping the dictionary into JSON file
  • Loading the JSON file or a JSON string
    • Loading the JSON string
    • Loading the JSON file

introduction to JSON

• JSON (JavaScript Object Notation) is a light weight data interchange format inspired by Javascript object literal syntax.
• A JSON file contains an object or an array that can contain different levels of nesting.
• Keys are string and are surrounded with double quotes ".

JSON Data Types and its python equivalent

SN	JSON Data Type	JSON Example	Python Equivalent	Python Example
1	number	1, 2.5	int or float	1, 2.5
2	string	"John"	str	'john'
3	boolean	true or false	bool	True or False
4	object	{"key": "value"}	dict	{'key': 'value'}
5	arrray	[1,2,3]	list, tuple	[1,2,3]
6	null	null	None	None

JSON basic Example

{
    "name": "John Doe",
    "age": 20,
    "married": true,
    "children": null
}

JSON example with nested objects

{
    "name": "Grade 1",
    "session": 2022,
    "class_teacher": "John Lennon",
    "students": [
        {
            "id": 1,
            "name": "John Doe",
            "subjects": [
                "Physics",
                "Mathematics"
            ]
        },
        {
            "id": 2,
            "name": "Jane Doe",
            "subjects": [
                "Chemistry",
                "Biology"
            ]
        }
    ]
}

Dumping Python dictionary into a json string or a file

person = {
    "name": "John Doe",
    'age': 20,
    'married': False,
    'occupation': 'programmer',
    'programming_languages': [
        {
            "name": "Python",
            "version": 3.9,
            'level': "Beginner",
        },
        {
            "name": "Java",
            "version": 17,
            'level': "Expert",
        },
        {
            "name": "C++",
            "version": 2019,
            'level': "Mid",
        },
    ]
}

Dumping the dictionary into JSON string

We can dump the python dictionary or a list into JSON string using json.dumps() method.

import json

json_str = json.dumps(person)

Dumping the dictionary into JSON file

We can dump the python dictionary or a list into JSON file using json.dump() method.

To dump the dictionary into the json file, we need to open file in a write mode.

import json

with open("filename.json", 'w') as file:
    json.dump(person, file)

The above command saves the output in the file filename.json inside the current working directory.

Loading the JSON file or a JSON string

Loading the JSON string

we can load the JSON string into python equivalent data using json.loads() method.

import json

json_string = '{"name": "John", "age": 20}'
dict_1 = json.loads(json_string)

Loading the JSON file

we can load the JSON file into python equivalent data using json.load() method.

To load the dictionary from the json file, we need to open file in a read mode.

import json

with open("filename.json", 'r') as file:
    dict_1 = json.load(file)