json.dump writes to an open file. Add indent=2 and a person can read the result too.
python
import json settings = {"theme": "dark", "font_size": 14, "recent": ["notes.py", "app.py"]} with open("settings.json", "w", encoding="utf-8") as f: json.dump(settings, f, indent=2) with open("settings.json", encoding="utf-8") as f: print(f.read())
output
{
"theme": "dark",
"font_size": 14,
"recent": [
"notes.py",
"app.py"
]
}Want the text instead of a file, say to send in a request or write to a log? json.dumps(settings) returns it as a string.
Names that aren't plain English
By default every non-ASCII character is escaped, so Zoë is written as Zo\u00eb. It's valid, but nobody can read it. ensure_ascii=False keeps the real characters; keep encoding="utf-8" on the file when you use it.
python
import json print(json.dumps({"name": "Zoë", "city": "São Paulo"})) print(json.dumps({"name": "Zoë", "city": "São Paulo"}, ensure_ascii=False))
output
{"name": "Zo\u00eb", "city": "S\u00e3o Paulo"}
{"name": "Zoë", "city": "São Paulo"}"Object of type date is not JSON serializable"
JSON only knows strings, numbers, booleans, null, lists and objects. A date, a Decimal or a set has no JSON form, so dump refuses.
python
import json from datetime import date order = {"id": "A-1001", "placed": date(2026, 10, 7)} try: json.dumps(order) except TypeError as e: print(e) print(json.dumps(order, default=str))
output
Object of type date is not JSON serializable
{"id": "A-1001", "placed": "2026-10-07"}default=str means "for anything you can't handle, use its string form". For dates that gives ISO format, which every language can parse back. For a set, convert it with list() yourself first.