Question

I’m quite new to python (I use python 3), and i’m trying to serialize a class with one string and two lists as members in JSon. I found that there’s a json lib in the python standart but it seems that I need to manually implement a serialization method. Is there a JSon encoder where I can simply pass an object, and receive the serialized object as string without having to implement a serialization method.
Example:

class MyClass:
    pass

if __name__ == '__main__':
    my_name = "me"
    my_list = {"one","two"}
    my_obj = MyClass()
    my_obj.name = my_name;
    my_obj.my_list = my_list


    serialized_object = JSONserializer.serialize(my_obj).

Thank you.

Answer 1

Don’t know of anything pre-built, but you can write one if your objects are simple enough. Override the default method in the JSONEncoder to look at inspect.getmembers(obj) (inspect is a more readable way of getting at sets of attributes in __dict__).

#!/usr/bin/env python3

import inspect
from json import JSONEncoder


class TreeNode:

    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right


class ObjectJSONEncoder(JSONEncoder):

    def default(self, reject):
        is_not_method = lambda o: not inspect.isroutine(o)
        non_methods = inspect.getmembers(reject, is_not_method)
        return {attr: value for attr, value in non_methods
                if not attr.startswith('__')}


if __name__ == '__main__':
    tree = TreeNode(42,
        TreeNode(24),
        TreeNode(242),
    )
    print(ObjectJSONEncoder().encode(tree))

Update: @Alexandre Deschamps says isroutine works better than is method for some input.