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JSON (JavaScript Object Notation)

SFBy Sitraka Forler · Lecturer, Durham Business School·Updated 13 September 2026· About this site

A plain-text format for structured data, built from objects, arrays and simple values.

JSON is the usual format for web APIs (application programming interfaces) and many config files, and it maps neatly onto Python dicts and lists. Values are objects, arrays, strings, numbers, true, false or null, and every key is a double-quoted string. Comments, trailing commas, single quotes and NaN (not a number) are all invalid, even though Python's json.dumps writes NaN by default.

{
  "trade_id": "T-1001",
  "currency": "EUR",
  "quantity": 10,
  "prices": [101.5, 102.25],
  "settled": true,
  "comment": null
}