Reacts' useEffect hook, written in python [naive implementation]

useEffect.py

#!/usr/bin/env python3


class Observable:
    def __init__(self, value):
        self._value = value
        self._subscribers = []

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, value):
        self._value = value
        for subscriber in self._subscribers:
            subscriber()


class Observer:
    def __init__(self, observable, callback):
        self._observable = observable
        self._callback = callback
        self._observable._subscribers.append(self)

    def __call__(self):
        self._callback()


class UseEffect:
    def __init__(self, callback, depdenency_array):
        self._observers = []
        self._callback = callback
        for dep in depdenency_array:
            observer = Observer(dep, self._callback)
            self._observers.append(observer)


def foo():
    global x
    print("x changed to", x.value)


x = Observable(10)
hook = UseEffect(foo, [x])
x.value = 20
x.value = 30
x.value = 40
x.value = 50