In Python, the scope ( Public, Protected, Private) characteristic of an attribute or member of the class is indicated by “the naming conventions of the member”. These are the naming conventions

Public: This means the member can be accessed outside of the class by other instances. The naming convention denotes that it has no underscores eg numberOfFields = 6 Protected: This means that the member can be accessed by the Parent Class and its “Children” – those classes that inherit the parent class The naming convention denotes that it has ONE underscore in front of the member name eg _numberOfFields = 6 Private This means the member is only accessible within the parent class. The naming convention denotes that it has TWO underscores in front of the member name eg __numberOfFields = 6

Lets check some examples

Let’s create a Car class and a BMW class the inherits from the Car Class

class Car:
    numberOfWheels = 4
    _colour = "Black"  #protected attribute
    __yearOfManufacture = '2017' ## private

class BMW(Car):
    def __init__(self):
        print("Protected attribute colour of car is :{} and the car has {}".format(self._colour, self.numberOfWheels))

 

Lets instantiate both classes and see how the attributes behave

car = Car()
print("Public attribute {}".format(car.numberOfWheels))

Public attribute 4

bmw = BMW()

Protected attribute colour of car is :Black and the car has 4

 

Lets access the private variable outside of the class

print("Accessing the private variable: ", car.__yearOfManufacture)

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-21-f33c89bb066a> in <module>()
----> 1 print("Accessing the private variable: ", car.__yearOfManufacture)

AttributeError: Car instance has no attribute '__yearOfManufacture'

 

Though we are strongly advised not to use the private variable outside of the class we can actually access it like below

print("Accessing the private variable YearOfManufacture: ", car._Car__yearOfManufacture)

('Accessing the private variable YearOfManufacture: ', '2017')

 

 

The full code can be found below:

Credit to Four Pillars of Object Oriented Programming on Udemy