Overriding vs Non-overriding Descriptors

• Overriding descriptors are descriptors that implement __set__. Therefore, the user can’t shadow any attribute that is defined as an overriding descriptor because any assignment at the to the instance’s attribute will be forced to go through the __set__ method. The below class utilizes @property, which is an overriding descriptor, to make an attribute as a read-only attribute.

class Test:
    def __init__(self):
        self._x = 1
    
    @property
    def x(self):
        return self._x

c = Test()
print(c.x)  #=> 1
c.x = 10    #=> AttributeError: can't set attribute 'x'

• Non-overriding descriptors are descriptors that don’t implement __set__. This means that the user can shadow the attribute. The common example of a non-overriding descriptor is the instance methods. They are actually implemented using non-overriding descriptor with __get__ method.

class Test:
    def f(self):
        return 1

c = Test()
type(c.f)   #=> method
print(c.f())    #=> 1

c.f = 0
type(c.f)   #=> int
print(c.f)  #=> 0