Understanding object-oriented programming

Before you start learning about design patterns, it's always good to cover the basics and go through object-oriented paradigms in Python. The object-oriented world presents the concept of objects that have attributes (data members) and procedures (member functions). These functions are responsible for manipulating the attributes. For instance, take an example of the Car object. The Car object will have attributes such as fuel level, isSedan, speed, and steering wheel and coordinates, and the methods would be accelerate() to increase the speed and takeLeft() to make the car turn left. Python has been an object-oriented language since it was first released. As they say, everything in Python is an object. Each class instance or variable has its own memory address or identity. Objects, which are instances of classes, interact among each other to serve the purpose of an application under development. Understanding the core concepts of object-oriented programming involves understanding the concepts of objects, classes, and methods.

Objects

The following points describe objects:

• They represent entities in your application under development.
• Entities interact among themselves to solve real-world problems.
• For example, Person is an entity and Car is an entity. Person drives Car to move from one location to the other.

Classes

Classes help developers to represent real-world entities:

• Classes define objects in attributes and behaviors. Attributes are data members and behaviors are manifested by the member functions
• Classes consist of constructors that provide the initial state for these objects
• Classes are like templates and hence can be easily reused

For example, class Person will have attributes name and age and member function gotoOffice() that defines his behavior for travelling to office for work.

Methods

The following points talk about what methods do in the object-oriented world:

• They represent the behavior of the object
• Methods work on attributes and also implement the desired functionality

A good example of a class and object created in Python v3.5 is given here:

class Person(object):
    def __init__(self, name, age):  #constructor
        self.name = name    #data members/ attributes
        self.age = age
    def get_person(self,):   # member function
         return "<Person (%s, %s)>" % (self.name, self.age)


p = Person("John", 32)    # p is an object of type Person
print("Type of Object:", type(p), "Memory Address:", id(p))

The output of the preceding code should look as follows: