typed_property with default and default_factory

code.py

from typing import Any, Union, Callable

SENTINEL = object()


def typed_property(
        name: str,
        default: Any = SENTINEL,
        default_factory: Union[Callable, SENTINEL] = SENTINEL
):
    if default is SENTINEL and default_factory is SENTINEL:
        raise TypeError("Choose to use either default or its factory, not both!")
    elif default is SENTINEL:
        default = default_factory()
    else:
        default = None

    varname = "_" + name

    @property
    def prop(self):
        if not hasattr(self, varname):
            setattr(self, varname, default)
        return getattr(self, varname)

    @prop.setter
    def setter(self, value):
        setattr(self, varname, value)

    return prop


class MyClass:
    data = typed_property("data", default_factory=dict)


class MyOtherClass:
    data = typed_property("data", default={1: 1})