descriptor.py

# In The Name Of God
# ========================================
# [] File Name : descriptor.py
#
# [] Creation Date : 19-10-2016
#
# [] Created By : Parham Alvani (parham.alvani@gmail.com)
# =======================================


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):
    def __init__(self):
        self.x = RevealAccess(10, 'var "x"')
        self.y = 5


m = MyClass()
print(m.x)