Lib/json/__init__.py

cpython 3.14 @ ab2d84fe1023/Lib/json/__init__.py ↗

Lib/json/__init__.py is the entry point for the json package. It provides dumps, loads, dump, and load as thin wrappers over JSONEncoder and JSONDecoder. The speed-critical string scanning and encoding paths live in Modules/_json.c.

Map

Lines	Symbol	Role
1-50	Re-exports	JSONDecodeError, JSONEncoder, JSONDecoder
51-150	dumps, dump	Encode Python object to JSON string or file
151-250	loads, load	Decode JSON string or file to Python object
251-360	Module-level docs	Parameter reference

Reading

dumps parameters

# CPython: Lib/json/__init__.py:183 dumps
def dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True,
          allow_nan=True, cls=None, indent=None, separators=None,
          default=None, sort_keys=False, **kw):
    ...
    if cls is None:
        cls = JSONEncoder
    return cls(
        skipkeys=skipkeys, ensure_ascii=ensure_ascii,
        check_circular=check_circular, allow_nan=allow_nan, indent=indent,
        separators=separators, default=default, sort_keys=sort_keys,
        **kw).encode(obj)

cls allows a custom encoder; passing cls=MyEncoder is the standard way to extend JSON serialization without monkey-patching.

default() hook

JSONEncoder.default(obj) is called when an object is not natively serializable. The default implementation raises TypeError. Override it to return a serializable representation.

object_hook and object_pairs_hook

JSONDecoder(object_hook=fn) calls fn(dict) on every JSON object, allowing custom deserialization. object_pairs_hook receives an ordered list of (key, value) pairs, useful for preserving key order or building custom mapping types.

allow_nan

When allow_nan=True (the default), NaN, Infinity, and -Infinity are encoded as JavaScript literals (not valid JSON). When False, they raise ValueError. Similarly on decoding, nan and inf tokens are accepted by default.

gopy notes

Not yet ported. module/json/ is planned. The encoder and decoder both depend on Modules/_json.c speed paths; the Go port will use encoding/json as the backend, adjusting for CPython's NaN/Inf handling and the object_hook callback.