jsonpickle returns False on check instance

Question

I wonder why the jsonpickle-module when consecutively applying or calling encode & decode does not pass the isinstance(...) check in Python 3.8.

Let say i have a simple class Person.

Here some code to illustrate what i mean:

import jsonpickle


class Person:
    id: int = -1
    name: str = "John Doe"

    def __init__(self, pId: int = None, name: str = None) -> None:
        self.id = (pId, self.id)[pId is None]
        self.name = (name, self.name)[name is None]


testInstance = Person()
testInstanceJSON = jsonpickle.encode(testInstance, unpicklable=True, make_refs=True)
print(testInstanceJSON)
testInstanceObject = jsonpickle.decode(testInstanceJSON)
print(testInstanceObject)
print(isinstance(testInstanceObject, Person.__class__))

It returns False on the last print-command!

You test if it is of the same (or derived) class as the **class of Person** but the class of a class is "type". — Michael Butscher, Sep 08 '21 at 16:13
@MichaelButscher Thanks for replying, but how to make it pass the isinstance(...) check, what should i do ? Or can i just use `print(type(testInstanceObject) == Person.__class__)`, it,s that what you exactly mean ? — Manifest Man, Sep 08 '21 at 16:26
Remove the `.__class__`. `Person` is already the class which "testInstanceObject" should be an instance of. — Michael Butscher, Sep 08 '21 at 16:32
Right i got it `print(isinstance(testInstanceObject, Person))` returns `True` as expected. ` — Manifest Man, Sep 08 '21 at 16:34
Make sure to write an answer, so i can mark it accordently @MichaelButscher — Manifest Man, Sep 08 '21 at 16:35

score 1 · Accepted Answer · answered Sep 08 '21 at 16:45

The attribute __class__ of an object provides the class the object is an instance of.

Classes like Person are also objects and instances of type.

This means that

isinstance(testInstanceObject, Person.__class__)

is the same as

isinstance(testInstanceObject, type)

but of course testInstanceObject is not an instance of type.

Change it to

isinstance(testInstanceObject, Person)

to check if testInstanceObject is an instance of Person.

jsonpickle returns False on check instance

1 Answers1