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Serialize JSON with sorted keys

Convert Python objects to JSON strings with object keys sorted for deterministic output.

Python practice15 minModules & Standard LibraryIntermediateLast updated March 23, 2026

Problem statement

Write a function json_sorted(obj) that serializes a Python object to a JSON string where the keys of all JSON objects are sorted. Use standard JSON encoding semantics (e.g., None -> null, True/False -> true/false). The output should be deterministic so the same input always produces the same string representation.

Task

Implement json_sorted(obj) that returns a JSON string with object keys sorted lexicographically (applies recursively to nested objects).

Examples

Sort top-level keys

Input

json_sorted({'b': 2, 'a': 1})

Output

{"a": 1, "b": 2}

Top-level object keys are sorted alphabetically in the resulting JSON string.

Input format

A Python object composed of dicts, lists, strings, numbers, booleans, and None passed to json_sorted(obj)

Output format

A JSON-formatted string with object keys sorted

Constraints

- Use only the Python standard library. - Maintain JSON semantics. - The serialized string must be deterministic for the same input. - Keep default spacing produced by json.dumps for readability.

Samples

Sample 1

Input

json_sorted({'b':1, 'a':2})

Output

{"a": 2, "b": 1}

Keys 'a' and 'b' are ordered in the output string.