Python create dictionary from nested class in list

Question

I am trying to store information about a class in a file. From what I've read, the data is typically converted into a dictionary using instance.__dict__. But the problem is my class contains classes nested inside. For example:

Class1:
    # Example data members
    data = None
    a = 0
    b = 0
    def __init__(self, data, a, b):
        self.data = data
        self.a = a
        self.b = b

Class2:
    x = 0
    y = 0
    def __init__(self, x, y):
        self.x = x
        self.y = y

nested_class = Class2(5, 10)
exterior_class = Class1(nested_class, 10, 15)

Now for the sake of keeping things clear, I am going to refer to the example (instead of the data I am actually working with because its more complicated). If I want to save Class1 in a .json, I cannot use json.dump because it cannot convert the class into a storage format. You can use the above method I mentioned but it won't convert the Class2 into a dictionary. Does anybody know of a better way to solve this issue without having to individually convert each nested class into a dictionary and then back when I need to use them as actual classes and not dictionaries (For the record, I have three layers of nested classes in my actual scenario, so an efficient solution will be appreciated)

Niel Godfrey P. Ponciano · Accepted Answer · 2021-09-05 03:33:42Z

You can use the default argument of json.dumps() to get the __dict__ of an attribute that can't be serialized, such as a nested class object.

If specified, default should be a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError. If not specified, TypeError is raised.

import json


class Class1:
    # Example data members
    data = None
    a = 0
    b = 0
    def __init__(self, data, a, b):
        self.data = data
        self.a = a
        self.b = b


class Class2:
    x = 0
    y = 0
    def __init__(self, duo, x, y):
        self.duo = duo
        self.x = x
        self.y = y


class Class3:
    def __init__(self, name1, name2):
        self.name1 = name1
        self.name2 = name2


level3 = Class3("John Lennon", "Paul McCartney")
level2 = Class2(level3, 5, 10)
level1 = Class1(level2, 10, 15)

def to_serializable(val):
    if hasattr(val, '__dict__'):
        return val.__dict__
    return val

print(json.dumps(level1.__dict__, default=to_serializable))

Output (pretty printed with an indentation of 4):

{
    "data": {
        "duo": {
            "name1": "John Lennon",
            "name2": "Paul McCartney"
        },
        "x": 5,
        "y": 10
    },
    "a": 10,
    "b": 15
}

Collectives™ on Stack Overflow

Python create dictionary from nested class in list

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related