Use of OOP in Python

Classes and Objects

Python is an object-oriented programming language. Everything in Python is associated with classes and objects, along with its attributes and methods. For example: in real life, a car is an object. The car has attributes, such as weight and color, and methods, such as drive and brake.

A Class is like an object constructor, or a "blueprint" for creating objects.

class Car: # class definition
  def __init__(self, modelYear, modelName):
    self.modelYear = modelYear
    self.modelName = modelName

An object is created from a class. We can create many objects from a class. An object is also called an instance of a class.

myCar = Car(1969, "Mustang") # create an object of Car
print(myCar.modelYear, myCar.modelName) # output the value of the modelYear and modelName attributes

PC $ python main.py
 
1969 Mustang

Encapsulation

Encapsulation in Python is a mechanism of wrapping the data (variables) and code acting on the data (methods) together as a single unit.

In encapsulation, the variables of a class will be hidden from other classes, and can be accessed only through the methods of their current class. Therefore, it is also known as data hiding.

There are 3 access modifiers in Python:

private: The code is only accessible within the declared class.
public: The code is accessible from all classes.
protected: The code is accessible in the same package and subclasses.

Private Variables

class Person:
  def __init__(self):
    self.__name = "John" # private variable
 
myObj = Person()
print(myObj.__name) # error

$ python main.py
Traceback (most recent call last):
  File "main.py", line 6    , in <module>
    print(myObj.__name) # error
AttributeError: 'Person' object has no attribute '__name'

Public Variables

class Person:
  def __init__(self):
    self.name = "John" # public variable
 
myObj = Person()
print(myObj.name) # John

$ python main.py
John

Protected Variables

class Person:
  def __init__(self):
    self._name = "John" # protected variable
 
myObj = Person()
print(myObj._name) # John

$ python main.py
John

OOPS - Concept Collections