JSONEncoder.default

json

method of JSONEncoder (source)

JSONEncoder.default(o)

Implement this method in a subclass such that it returns
a serializable object for ``o``, or calls the base implementation
(to raise a ``TypeError``).

For example, to support arbitrary iterators, you could
implement default like this::

    def default(self, o):
        try:
            iterable = iter(o)
        except TypeError:
            pass
        else:
            return list(iterable)
        # Let the base class default method raise the TypeError
        return super().default(o)

© Python Software Foundation. PSF License Version 2 · Official docs ↗

1 Example

link / history / report

>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
...     def default(self, obj):
...         if isinstance(obj, complex):
...             return [obj.real, obj.imag]
...         # Let the base class default method raise the TypeError
...         return super().default(obj)
...
>>> json.dumps(2 + 1j, cls=ComplexEncoder)
'[2.0, 1.0]'
>>> ComplexEncoder().encode(2 + 1j)
'[2.0, 1.0]'
>>> list(ComplexEncoder().iterencode(2 + 1j))
['[2.0', ', 1.0', ']']

from the Python docs