Object-Oriented Programming

What Is Object-Oriented Programming?

• Object-Oriented Programming (OOP): Focuses on objects and message passing between them rather than just variables and functions.
• Classes and Objects:
  • Class: Blueprint for creating objects. Defines instance variables and methods.
  • Object: Instance of a class.

A class specifies the set of instance variables and methods that are “bundled together” for defining a type of object. A class, therefore, is a “cookie cutter” that can be used to make as many object instances of that type as needed. For example, strings in Python are object instances of the built-in String class

One method of the String class is isdigit. Thus, every string object has this method. The specific object whose isdigit method is called determines the specific string that it is applied to:

• name.isdigit() ➝ False
• city_state.isdigit() ➝ False
• address.isdigit() ➝ False
• zip_code.isdigit() ➝ True

Message passing

Message passing occurs when a method of one object calls a method of another.

For example, if Object B were a list and B1 a sorting method, then a call to B1 is a message (or request) for it to become sorted.

A message to one object can result in the propagation of messages among many other objects in order to accomplish a request.