Read, Write and Parse JSON using Python

JSON (JavaScript Object Notation) is a lightweight text format used to store and exchange structured data between applications. Python provides a built-in json module for reading, writing, parsing, and converting JSON data without installing an external package.

Understanding JSON

It represents structured data using objects, arrays, strings, numbers, Boolean values, and null. Python's json module converts JSON data into Python objects and vice versa.

{
    "name": "Aarav",
    "age": 22,
    "skills": ["Python", "SQL"],
    "is_student": true,
    "address": null
}

Explanation:

• Objects contain key-value pairs enclosed in curly braces.
• Arrays contain ordered values enclosed in square brackets.
• JSON property names and string values use double quotation marks.
• JSON uses true, false, and null instead of Python's True, False, and None.

Parsing JSON strings

Parsing converts a JSON-formatted string into a Python object. The json.loads() function is used when JSON data is already available as a string.

import json

json_text = '{"name": "Aarav", "age": 22, "skills": ["Python", "SQL"]}'

data = json.loads(json_text)

print(data)
print(data["name"])
print(data["skills"][0])

Output

{'name': 'Aarav', 'age': 22, 'skills': ['Python', 'SQL']}
Aarav
Python

Explanation:

• json.loads() parses the JSON string and returns a Python dictionary.
• Dictionary keys provide access to individual values.
• List indexing retrieves items from the skills array.

Reading JSON data

json.load() function reads a JSON document from an open file and converts it into a Python object. Use a with statement to ensure that the file is closed automatically.

import json

with open("student.json", "r", encoding="utf-8") as file:
    data = json.load(file)

print(data)
print(data["name"])
print(data["skills"])

Output

{'name': 'Aarav', 'age': 22, 'skills': ['Python', 'SQL']}
Aarav
['Python', 'SQL']

Explanation:

• open() opens the file in read mode.
• json.load() reads and parses the JSON document.
• Resulting dictionary supports normal Python operations, including key access and list indexing.

Converting Python Objects into JSON Strings

json.dumps() function serializes a Python object into a JSON-formatted string. This is useful when data needs to be prepared for transmission, logging, or further processing.

import json

data = {
    "name": "Aarav",
    "age": 22,
    "skills": ["Python", "SQL"]
}

json_text = json.dumps(data, indent=4, sort_keys=True)

print(json_text)
print(type(json_text))

Output

Explanation:

• json.dumps() returns a string rather than writing directly to a file.
• indent=4 formats the output with four spaces per indentation level.
• sort_keys=True arranges object keys in sorted order.
• type() confirms that the resulting value is a Python string.

Writing JSON data

json.dump() function serializes a Python object and writes the JSON representation directly to an open file. This is useful for saving application settings, records, and processed data.

import json

data = {
    "name": "Aarav",
    "age": 22,
    "skills": ["Python", "SQL"]
}

with open("output.json", "w", encoding="utf-8") as file:
    json.dump(data, file, indent=4, ensure_ascii=False)

print("JSON data written successfully.")

Output

JSON data written successfully.

Explanation:

• json.dump() writes the serialized data into the file.
• write mode ("w") creates the file if it does not exist and replaces its existing contents if it does.
• indent=4 makes the file easier to read.
• ensure_ascii=False preserves non-ASCII characters directly in the output.

Loading Methods

Handling JSON Errors

Invalid JSON can cause json.load() or json.loads() to raise a JSONDecodeError. File operations may also raise FileNotFoundError when the requested file is missing.

import json

json_text = '{"name": "Aarav", "age": }'

try:
    data = json.loads(json_text)
    print(data)

except json.JSONDecodeError as error:
    print("Invalid JSON:", error.msg)

Output

Invalid JSON: Expecting value

Explanation:

• JSON string is invalid because age has no value.
• json.loads() raises JSONDecodeError when it cannot parse the document.
• Except block catches the exception and displays a meaningful message.