Using with statement in python [duplicate]

Hey guys am trying to use the with statement in my code..Since am new to python i just wrote to code to understand the working of with statement..My code

class Employee:
    empCount = 0
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary


c = Employee("blah",1)
c.empCount = ['aad']




class Subin(Employee):

    def __init__(self, name, salary):
        self.name = name
        self.salary = salary


    def __enter__(self):
        return self

    def __exit__(self ,type):
        print 'ok'


    def babe(self):
        with c.empCount as b:
            return 0

b = Subin("sds",1)
b.babe()

When I run the code I get the error:

Traceback (most recent call last):
  File "C:/Python27/dfg", line 38, in <module>
    b.babe()
  File "C:/Python27/dfg", line 33, in babe
    with c.empCount as b:
AttributeError: __exit__

Can you guys tell me why this is happening?