What is JSON?
Understand the JSON format and how it maps to Python data structures
JSON and Python
JSON (JavaScript Object Notation) is a text format for representing structured data. It is used everywhere — API responses, configuration files, database exports, and web services all use JSON.
The best thing about JSON for Python developers: JSON maps directly to Python's built-in types.
| JSON | Python |
|---|---|
{} object | dict |
[] array | list |
"string" | str |
42 number | int |
3.14 number | float |
true / false | True / False |
null | None |
JSON structure
JSON supports nesting — objects can contain arrays, arrays can contain objects.
{
"user": {
"name": "Alice",
"scores": [95, 88, 92],
"active": true
}
}Where JSON appears
- API responses — nearly every web API returns JSON
- Config files — settings for apps and tools
- Data storage — structured records that don't fit in CSV
Python's json module
Python's built-in json module converts between JSON text and Python objects.
| Function | Direction |
|---|---|
json.load(file) | JSON file → Python object |
json.loads(string) | JSON string → Python object |
json.dump(obj, file) | Python object → JSON file |
json.dumps(obj) | Python object → JSON string |