Python JSON encoder convert NaNs to null instead

Question

I'm writing code to receive an arbitrary object (possibly nested) capable of being converted to JSON.

The default behavior for Python's builtin JSON encoder is to convert NaNs to NaN, e.g. json.dumps(np.NaN) results in NaN. How can I change this NaN value to null?

I tried to subclass JSONEncoder and override the default() method as follows:

from json import JSONEncoder, dumps
import numpy as np
    
class NanConverter(JSONEncoder):
    def default(self, obj):
        try:
            _ = iter(obj)
        except TypeError:
            if isinstance(obj, float) and np.isnan(obj):
                return "null"
        return JSONEncoder.default(self, obj)

>>> d = {'a': 1, 'b': 2, 'c': 3, 'e': np.nan, 'f': [1, np.nan, 3]}
>>> dumps(d, cls=NanConverter)
'{"a": 1, "c": 3, "b": 2, "e": NaN, "f": [1, NaN, 3]}'

EXPECTED RESULT: '{"a": 1, "c": 3, "b": 2, "e": null, "f": [1, null, 3]}'

Answer 1

This seems to achieve my objective:

import simplejson


>>> simplejson.dumps(d, ignore_nan=True)
Out[3]: '{"a": 1, "c": 3, "b": 2, "e": null, "f": [1, null, 3]}'