1. Object Oriented Design and Classes

2. Exercises
Design a phone book program. Your program should keep track of the name and phone number of your contacts. You should be able to add new contacts to your phone book and view your phone book.

3. What is a class? Programming mechanism to support OOD
Data and the methods that operate on that data – collectively called members
Example: bank account class
Provide structure for organizing programs

4. Methods Methods operate on data An object in an instance of a class
accessors – read data, provide access to data but do not change it
mutators – change data
examples from bank account, zoo
constructor – builds a new object
An object in an instance of a class
class is a blueprint for objects

5. BankAccount Class class BankAccount:
def __init__(self, initial_balance):
self.balance = initial_balance
def deposit(self, amount):
self.balance += amount
def withdraw(self, amount):
self.balance -= amount
def checkBalance(self):
print "Balance: ", self.balance

6. BankAccount Class def __init__(self, initial_balance):
self.balance = initial_balance
__init__ method is the constructor
Used to initialize members of the object
First parameter is self – the object on which the method/constructor is called
Use dot notation (.) to reference members of the object

7. BankAccount Class def deposit(self, amount): self.balance += amount
def withdraw(self, amount):
self.balance -= amount
Deposit and withdraw are mutators
they modify the data member balance
First parameter is self
Like functions, methods can take any number of parameters

8. BankAccount Class def checkBalance(self):
print "Balance: ", self.balance
checkBalance does not modify data members

9. Creating and Using Objects
b = BankAccount(500)
//Name = Type(constructor parameters)

10. Creating and Using Objects
b = BankAccount(500)
//Name = Type(constructor parameters)
//how would you withdraw funds?
b.withdraw(500)
//object_name.method_name(params)

11. Composing Objects An object can have a reference to another object
class Name:
def __init__(self, first, last):
self.first = first
self.last = last
def printName(self):
print "Name: ", self.first, " ", self.last
class Employee:
def __init__(self, first, last, pay):
self.name = Name(first, last)
self.pay = pay
def printEmployee(self):
self.name.printName()
print "\tPay rate: ", self.pay

12. Exercises
Implement your phone book program.