Python · Chapter 33 of 45
Python JSON
JSON is a text format for structured data — the standard for web APIs. Python's built-in `json` module converts between JSON strings and Python objects.
`json.loads()` parses a string. `json.dumps()` serialises to a string.
Files
`json.load(file)` and `json.dump(obj, file)` work directly with file objects.
Mapping
dict ↔ object, list ↔ array, str ↔ string, int/float ↔ number, True/False ↔ true/false, None ↔ null.
Example 1 (python)
import json
data = {"name": "Ana", "roles": ["admin", "user"]}
text = json.dumps(data, indent=2)
print(text)Output
{
"name": "Ana",
"roles": [
"admin",
"user"
]
}Serialise a dict to pretty JSON.
Example 2 (python)
import json
json_str = '{"x": 1, "y": [2, 3]}'
obj = json.loads(json_str)
print(obj["y"])Output
[2, 3]Parse JSON string to a Python dict.
Key points
- `json.dumps(obj)` → string.
- `json.loads(str)` → object.
- `json.dump/load` for files.
- JSON keys are always strings.
💡 Note: Datetime and set are NOT JSON-serialisable by default — convert to string or list first.