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Python private attribute

To access an attribute a class instance needs to keep a reference to the attribute object. Because all attribute references are accessible via a class instance's __dict__, it seems impossible to implement private attribute. There is one way, however. The key is to put attribute references in a place inaccessible outside the class, by using closure:

def create_class():
    private_attributes = dict()

    class Class(object):
        def __init__(self):
            private_attributes[id(self)] = 0

        def __del__(self):
            try:
                del private_attributes[id(self)]
            except KeyError:
                pass

        def get_private_attribute(self):
            return private_attributes[id(self)]

        def set_private_attribute(self, value):
            private_attributes[id(self)] = value

    return Class

Class = create_class()

obj = Class()

assert obj.get_private_attribute() == 0

obj.set_private_attribute(1)

assert obj.get_private_attribute() == 1
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