Python JSON encoder - default method

Question

I want to make my class JSON serializeable and am trying to extend it with the JSONEncoder class. However, why does the default function take the o parameter when it is supposed to be a method of my class.

I want to serialize my class object, not a third object that is passed to the method?

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

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 JSONEncoder.default(self, o)

You don't extend your class with JSONEncoder, you extend JSONEncoder to handle your class. — glibdud
– glibdud, Commented Sep 1, 2017 at 18:22
The class you want to make serializable isn't suppose to inherit from JSONEncoder... that is your fundamental misunderstanding. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Sep 1, 2017 at 18:22

Moher · Accepted Answer · 2017-09-01 18:33:34Z

1

you should do something like this:

>>> 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 json.JSONEncoder.default(self, obj)

maybe you're forgetting json at last return.
take a look at json doc

edited Sep 1, 2017 at 18:33

answered Sep 1, 2017 at 18:24

Moher

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