How I can create reference to member of the class instance?

[AlekseyPython]

Python 3.7.1

I wrote this class:

class Cycler(object):
    def __init__(self, data):
        self.data = data

    def do(self):
        My_ref = self.data
        My_ref = 2

And now I want create small name to simplify the code. In above code the instance self does not change the value of the variable data (but variable My_ref will now refer to an object of type 'int' with a value of 2).

How I can create writable reference to a member of the class instance?