Read and write JSON

JSON can represent objects, arrays, strings, numbers, true or false, and null. Python’s json module converts between JSON text and matching Python values. Use dumps() to create JSON text and loads() to parse it.

For file practice, download the Python practice files v1.0.0 bundle. The examples write their own files, so the samples stay unchanged. Work on a copy if you edit a sample.

import json

settings = {"subject": "Python", "minutes": 25}
encoded = json.dumps(settings)
restored = json.loads(encoded)
print(restored["subject"])
print(restored["minutes"] + 5)

Python
30

Save JSON to a file

Write UTF-8 JSON with pathlib, then load it back. json.dumps(..., indent=2) makes the saved file easier to read. Writing replaces an existing file at that path.

import json
from pathlib import Path

path = Path("my_settings.json")
path.write_text(json.dumps({"goal": 3}, indent=2), encoding="utf-8")
loaded = json.loads(path.read_text(encoding="utf-8"))
print(loaded["goal"])

3

Why this works

json.dumps() converts Python values to JSON text, and json.loads() converts JSON text back to Python values. A JSON object usually becomes a Python dictionary and a JSON array becomes a list. Loading a numeric JSON value gives a number, unlike the text fields returned by csv.reader.

Practice

Save a dictionary with your subject and planned sessions to a JSON file. Read it back and print the values. Use a practice filename so you do not replace an important file. Then load the sample settings.json from the practice bundle and print its minutes plus 5; you should see 30.

Try another case

After loading {"goal": 3} from JSON, can you add 2 to the goal without int()?