Python JSON encoder that makes more of an effort to encode non-builtin types

betterjsonencoder.py

from json import JSONEncoder
from numbers import Integral, Real
from collections.abc import Sequence, Mapping


class BetterJSONEncoder(JSONEncoder):
	"""JSON encoder that makes more of an effort to encode non-builtin types."""

	def default(self, o):

		# Check bool subclasses first, as they are also considered integers.
		if isinstance(o, bool):
			return bool(o)

		# Check numeric ABCs, most specific first
		if isinstance(o, Integral):
			return int(o)

		if isinstance(o, Real):
			return float(o)

		# Check sequence and mapping ABCs
		if isinstance(o, Sequence):
			return list(o)

		if isinstance(o, Mapping):
			return dict(o)

		# Subclass of plain old str. Probably disjoint from all other
		# possibilities here.
		if isinstance(o, str):
			return str(o)

		# Sequence protocol
		# Check before __index__, Numpy arrays don't subclass Sequence and
		# have an __index__ method (which raises an error on array with more
		# than one element).
		if hasattr(o, '__len__') and hasattr(o, '__getitem__'):
			return list(o)

		# Presence of this method indicates the object is an integer (according
		# to the standard, but Numpy arrays don't obey this).
		if hasattr(o, '__index__'):
			return int(o)

		# Both float and int types have both of the following methods, so in the
		# absence of the __index__ method prioritize __float__.
		if hasattr(o, '__float__'):
			return float(o)

		if hasattr(o, '__int__'):
			return int(o)

		return super().default(o)