class RevealAccess(object):
    """A data descriptor that sets and returns values
       normally and prints a message logging their access.
    """
 
    def __init__(self, initval=None, name='var'):
        self.val = initval
        self.name = name
 
    def __get__(self, obj, objtype):
        print('Retrieving', self.name)
        return self.val
 
    def __set__(self, obj, val):
        print('Updating', self.name)
        self.val = val
 
class MyClass(object):
    x = RevealAccess(10, 'var "x"')
    y = 5
 
m = MyClass()
 
print(m.x)
 
m.x = 20
 
print(m.x)
print(m.y)

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