Object Oriented Programming in Python

Classes and Instances
Class Variables
Classmethods and Staticmethods
Creating Subclasses
Special (Magic/Dunder) Methods
Property Decorators-Getters, Setters and Deleters

NOTES

01. Classes and Instances

Classes

Classes are the building blocks in Object Oriented Programming. Classes allow us to logically group our data and functions in a way that is easy to reuse and also easy to build upon if need be.
Instances

An Instance is a concrete occurrence of any object. Classes can be seen as blueprints from which you create your Instances.

02. Class Variables

Attributes or methods specific to a class are called Class attributes

For example :

 class Employee:
    num_of_emps = 0                 
    raise_amount = 1.04            
    def __init__(self,fname,lname,salary):                             
        self.fname = fname
        self.lname = lname
        self.salary = salary
        Employee.num_of_emps += 1

Here no_of_emps and raise_amount are class attributes. These are used when certain values need to be set outside a function.

03. Class and Static Methods

Class Methods

Class methods:takes the first argument as the class, these are created using decoraters @classmethod. Creating class method using decorater
```
  @classmethod
  def set_raise_amt(cls,amount):
      cls.raise_amount = amount 
```
Static Methods

A static method can't access or modify the class state. Static methods does not automatically passes the first argument as self these act as regular functions ,we add them to the class as they have logical connection with the class in order to create the static method the decorater @staticmethod is used.

04. Inheritance-Creating Subclasses

Inheritance

Inheritance allows us to inherit attributes and methods from the parent class this is used to create sub classes and get the functionality of our parent class without writing the same thing more than once withhout affecting parent class in any way.

Creating-Subclasses

Syntax for creating subclass --> class classname(inherited from)

For example:

class Developer(Employee): #subclass Developer inherited from class Employee
      raise_amount = 1.05
      def __init__(self,fname,lname,salary,prog_lang):
          super().__init__(fname,lname,salary)
          self.prog_lang = prog_lang

05. Special (Magic/Dunder) Methods

Special methods also known as magic methods these methods allow us to emulate some built-in within python and it's also how we implement operator overloading

For example:

print(4+6) and print('a'+'b') ,these two statements will have different result still using same operator but getting different results this is known as operator overloading.

Special methods use double underscore __init__ also known as dunder two more common dunder special methods are dunder :

repr() : is met to be an unambiguous representation of the object and should be used for thing like logging and debugging etc....
str() : is a more of a readable representation of an object and is meant to be used as a display to the end user.

06. Property Decorators -Getters, Setters and Deleters

Property Decoraters allow us to define a method but allow us to access it as a attribute.

Getters

A Getter is a method that gets the value of a property.

Setters

A Setter is a method that sets the value of a property

Setting fname and lname using Setter from a string.

 @fullname.setter 
  def fullname(self,name):
      fname,lname = name.split(" ")
      self.fname = fname
      self.lname = lname

Deleters

A Deleter is a method that deletes the value of a property.

Deleter for fullname

 @fullname.deleter
 def fullname(self): 
     print('Name Deleted!')
     self.fname = None
     self.lname = None

CREDITS

Thanks to Mr. Corey Schafer for his amazing playlist: Python OOP Tutorials - Working with Classes

devaaravmishra/oop-with-python

Object Oriented Programming in Python

Contents

NOTES

01. Classes and Instances

Classes

Instances