class CustomEncoder(*, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, default=None)[source]

Bases: json.encoder.JSONEncoder

Constructor for JSONEncoder, with sensible defaults.

If skipkeys is false, then it is a TypeError to attempt encoding of keys that are not str, int, float or None. If skipkeys is True, such items are simply skipped.

If ensure_ascii is true, the output is guaranteed to be str objects with all incoming non-ASCII characters escaped. If ensure_ascii is false, the output can contain non-ASCII characters.

If check_circular is true, then lists, dicts, and custom encoded objects will be checked for circular references during encoding to prevent an infinite recursion (which would cause an OverflowError). Otherwise, no such check takes place.

If allow_nan is true, then NaN, Infinity, and -Infinity will be encoded as such. This behavior is not JSON specification compliant, but is consistent with most JavaScript based encoders and decoders. Otherwise, it will be a ValueError to encode such floats.

If sort_keys is true, then the output of dictionaries will be sorted by key; this is useful for regression tests to ensure that JSON serializations can be compared on a day-to-day basis.

If indent is a non-negative integer, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. None is the most compact representation.

If specified, separators should be an (item_separator, key_separator) tuple. The default is (’, ‘, ‘: ‘) if indent is None and (‘,’, ‘: ‘) otherwise. To get the most compact JSON representation, you should specify (‘,’, ‘:’) to eliminate whitespace.

If specified, default is a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError.



This method is used to serialize objects to JSON format.


Overriding of JSONEncoder.encode(), to make our own process.





This method is used to serialize objects to JSON format.

If obj is a function, then it will return a dict with two keys : ‘code’, for the code source, and ‘nonlocals’ for all nonlocalsvalues. (including nonlocals functions, that will be serialized as this is recursive.) if obj is a np.darray, it converts it into a list. if obj is an object with __dict__ attribute, it returns its __dict__. Else, will let the JSONEncoder do the stuff, and throw an error if the type is not suitable for JSONEncoder.


obj (Any) – Arbitrary object to convert


Python object that JSON encoder will recognize

Return type



Overriding of JSONEncoder.encode(), to make our own process.


obj (Any) – The object to encode in JSON.


The object encoder with the standard json process.

Return type