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How to read and write JSON

Updated September 2026 · Beginner-friendly guide

Understand the mapping

JSON objects become dictionaries, arrays become lists, and JSON strings, numbers, booleans, and null map to their Python counterparts.

import json

text = '{"name": "Ada", "active": true, "skills": ["math", "code"]}'
data = json.loads(text)
print(data["name"])
print(data["skills"][0])

Write JSON text

dumps() returns a string. Indentation makes it readable; sort_keys gives stable key order for display.

import json

record = {"score": 95, "name": "Ada", "active": True}
text = json.dumps(record, indent=2, sort_keys=True)
print(text)

Read and write files

load() and dump() work with file objects. Use UTF-8 and a with statement.

import json

settings = {"theme": "dark", "font_size": 16}
with open("settings.json", "w", encoding="utf-8") as file:
    json.dump(settings, file, indent=2)

with open("settings.json", encoding="utf-8") as file:
    loaded = json.load(file)
print(loaded["theme"])

Handle invalid or unsupported data

Malformed input raises JSONDecodeError. Objects such as sets and dates are not JSON serializable until converted to supported values.

import json

try:
    json.loads("{bad json}")
except json.JSONDecodeError as error:
    print(f"Invalid JSON at line {error.lineno}, column {error.colno}")

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