Python JSON Examples

Short, runnable programs that show working with json in python in action. Read the explanation, press Run, then change the code and try your own ideas. New to the topic? Start with the Working with JSON in Python lesson.

1Save and load a JSON file

json.dump() writes Python data to a file as JSON, and json.load() reads it back as an equal dict — the simplest way to keep data between runs.

Save and load a JSON file

import json

settings = {"theme": "dark", "font_size": 14, "autosave": True, "recent": ["notes.txt", "todo.txt"]}

with open("settings.json", "w") as f:
    json.dump(settings, f, indent=2)

with open("settings.json") as f:
    print(f.read())

with open("settings.json") as f:
    loaded = json.load(f)
print(loaded == settings, loaded["recent"][0])

Expected output{
  "theme": "dark",
  "font_size": 14,
  "autosave": true,
  "recent": [
    "notes.txt",
    "todo.txt"
  ]
}
True notes.txt

2Formatting options for dumps()

By default non-ASCII characters are escaped as \u codes. sort_keys=True orders the keys and ensure_ascii=False keeps characters such as é readable.

Formatting options for dumps()

import json

place = {"name": "Café Mila", "rating": 4.5, "city": "Lyon"}
print(json.dumps(place))
print(json.dumps(place, sort_keys=True))
print(json.dumps(place, ensure_ascii=False))

Expected output{"name": "Caf\u00e9 Mila", "rating": 4.5, "city": "Lyon"}
{"city": "Lyon", "name": "Caf\u00e9 Mila", "rating": 4.5}
{"name": "Café Mila", "rating": 4.5, "city": "Lyon"}

3Loop over a JSON array of records

APIs often return a list of objects. After json.loads() it is just a list of dicts, so comprehensions and loops work as usual.

Loop over a JSON array of records

import json

todos_json = '''[
  {"id": 1, "title": "Buy milk", "completed": false},
  {"id": 2, "title": "Pay rent", "completed": true},
  {"id": 3, "title": "Call mum", "completed": false}
]'''

todos = json.loads(todos_json)
pending = [todo["title"] for todo in todos if not todo["completed"]]
print(f"{len(pending)} of {len(todos)} tasks pending:")
for title in pending:
    print("-", title)

Expected output2 of 3 tasks pending:
- Buy milk
- Call mum

4Catch invalid JSON

json.JSONDecodeError tells you what went wrong. Catch it when the text comes from a user, a file or the internet.

Catch invalid JSON

import json

samples = ['{"ok": true}', "{'ok': true}", '{"ok": true,}']
for text in samples:
    try:
        print("Parsed:", json.loads(text))
    except json.JSONDecodeError as err:
        print("Invalid JSON:", err.msg)

Expected outputParsed: {'ok': True}
Invalid JSON: Expecting property name enclosed in double quotes
Invalid JSON: Illegal trailing comma before end of object

Practise next

Working with JSON in Python exercises → Back to the lesson

Python Dictionaries examples Python CSV Files examples Python requests: Call Web APIs examples Python API Example: Build an API Client examples