Abstraction and Encapsulation

Abstraction and Encapsulation

• Abstraction means working with something you know how to use without knowing how it works internally.

• Encapsulation allows binding data and associated methods together in a unit i.e class.

• These principles together allows a programmer to define an interface for applications, i.e. to define all tasks the program is capable to execute and their respective input and output data.

• A good example is a television set. We don’t need to know the inner workings of a TV, in order to use it. All we need to know is how to use the remote control (i.e the interface for the user to interact with the TV).

Abstracting Data

• Direct access to data can be restricted by making required attributes or methods private, just by prefixing it's name with one or two underscores.

• An attribute or a method starting with:

  • no underscores is a public one.

  • a single underscore is private, however, still accessible from outside.

  • double underscores is strongly private and not accessible from outside.

Abstraction and Encapsulation Example

class Employee(Person):
    all_employees = EmployeesList()
    def __init__(self, fname, lname, empid):
        Person.__init__(self, fname, lname)
        self.__empid = empid
        Employee.all_employees.append(self)
    def getEmpid(self):
        return self.__empid

Abstraction and Encapsulation Example Contd..

e1 = Employee('Jack', 'simmons', 456342)
print(e1.fname, e1.lname)
print(e1.getEmpid())
print(e1.__empid)

Jack simmons
456342
AttributeError: Employee instance has no attribute '__empid'