1. Object Oriented Programming In Python

2. Understanding Object Oriented Programming, or OOP
So far, you have written Python programs in a “Top Down” fashion using functions
Now we will learn a new way building and thinking about building software
OOP lets you represent real-life objects as software objects
You will combine characteristics (called attributes) and behaviors (called methods)

3. Alien Spacecraft Example
If you were to build an alien spacecraft, what would be it’s attributes and behaviors?

4. Alien Spacecraft Example
Attributes: Location, fuel level, engine temperature, current velocity, current direction
Behaviors: Move forward, move backward, move up, move down, fire weapons, teleport

5. Objects and Classes
Objects are created (or instantiated in OOP- Speak) from a definition called a class
Classes are like blueprints.
A class isn’t an object; it is a design for one
A builder can create many houses from one set of blueprints
A programmer can create many objects from one class

6. More on Objects and Classes
Separate objects can have separate attribute values
Just as two houses built from the same blueprint can be decorated differently, two objects of the same class can have their own attribute values

7. Bank Account Example A bank has one checking account class
Attributes: Name, account number, date created, balance
Methods: Make deposit, make withdrawl
Two objects can be instantiated for two different customers. Each may have their own account number and balance

8. Simple Python Example class Critter(object) : def talk(self):
print("Hi! I am a Critter")
def main():
crit = Critter()
crit.talk()
main()
Output:
Hi! I am a Critter

9. Creating A Constructor
A constructor is automatically called when the object is instantiated
class Critter(object) :
def __init__(self):
print("A new critter has been born!")
def talk(self):
print("Hi! I am a Critter")
def main():
crit = Critter()
crit.talk()
main()

10. Creating Multiple Objects
class Critter(object) :
def __init__(self):
print("A new critter has been born!")
def talk(self):
print("Hi! I am a Critter")
def main():
crit1 = Critter()
crit1.talk()
crit2 = Critter()
crit2.talk()
main()

11. Using Attributes
You can have attributes created and initialized when an object is instantiated
class Critter(object) :
def __init__(self, name):
print("A new critter has been born!")
self.name = name
def talk(self):
print("Hi! I am a ", self.name, " Critter")
def main():
crit1 = Critter("Dog")
crit1.talk()
crit2 = Critter("Cat")
crit2.talk()
main()

12. Why is OOP important?
Makes complex code easier to develop, more reliable, more maintainable and generally better
Encapsulation – Lets you change the implementation of an object without affecting other code

13. Why is oop important?
Polymorphism - Lets you have different functions, all with the same name, all doing the same job, but on different data
Inheritance – You can write a set of functions and then expand them in different directions without changing or copying them