Procedural Programming

• Procedural Programming is like a recipe
  • inputs
  • steps (sequence)
  • output

Object Oriented Programming

• Object:
  • contains
  • capabilities

Examples

• Bank Account

BankAccount
  contains:
     account number
     account type
     balance
  characteristics:
    transfer
    withdraw
    deposit

• Laptop

contains:
  configuration
     cpu
     ram
     storgae
  os
  features
characteristics:
  start
  shutdown
  browser
  ...
  ...

• Library

book
shelf
newspaper
transaction
librarian
user

• Object oriented programming has two important concepts
  • Class: Here we are building a cookie cutter/ design (Blueprint)
    • In programming world we write class to specify structure
  • Object: This is what we operate on (cookie/home/ac).
    • We create object from class and object has memory/cpu/resources attached to it.

Writing a class

• Class is a blueprint
  • members are contents (variables)
  • methods are capabilities (functions)
• Classes or objects can have relationships
• To classify these relationship all we have to figure out is
  • is-a relationship
  • has-a relationship
• Technically in OOD we have 4 types of relationships that can exist
  • Association: uses
  • Aggregation: Weak has-a
  • Composition: Strong has-a
  • Inheritence: is-a

Exercise

• Identify classes for Restaurant, we are supposed to build a Billing system
  • Restaurant
  • Menu
  • MenuItem
  • Tables list<Table>
  • Order
  • OrderItem
  • Bill
  • Payment
• Menu

contents:
   menu items

• Menu Item

contents:
  id
  category
  price
  name

• Table

content:
   number
   capacity

• Order

content:
  id
  list<orderItem>
  status
capability:
  generate_bill()
  cancel

• OrderItem

content:
  id
  menuitem_id
  quanity

• Bill

contents:
  id
  Order
  amount
  tax
  total
capabilites:
  pay()

UML Diagrams

• Refer Here for visual paradigm

Principles

• Abstraction
• Encapsulation
• Polymorphism
• SOLID
• DuckTyping (Python special)

Refer Here for the notebook created in the class