Object Oriented Programming Day 1

Learning Objectives

Students Will Be Able To...

Initialize a class
Call various methods from within a class
Import a class

Context

Python is an object oriented language.
It allows us to organize our code for efficiency and readability

Lesson

Part 1 - What is OOP?

Object Oriented Programming is the practice of writing your code around Objects
We will come back to this later in the lesson

Part 2 - What are Objects?

Everything in Python is an object
Every object is an instance of a class
We know about the various data types and data structures. Well take lists for example. The moment you create a list you made an instance of it. This list now has access to all the methods inside the list class of Python3
lists belong to a list class
strings belong to a string class
dictionaries belong to a dictionary class

Part 3 - Classes

And what is a class? Simply a logical grouping of data and functions (the latter of which are frequently referred to as "methods" when defined within a class).

A class holds many methods that an object can respond to.
They are defined with the word class
They are always capitalized
They are just blueprints for us to use later
Lets make a class example for Car
This car will take in three variables when created
This car will have access to a method called hello that will print the make, model, and year to the to your terminal

class Car:
	"""
	We are making a car class
	"""

	def __init__(self, make, model, year):
		self.make = make
		self.model = model
		self.year = year

	def hello(self):
		print("You have started your car, it is a {year} {make} {model}".format(year = self.year, make = self.make, model = self.model))

my_car = Car(make = "Bugatti", model = "Veyron", year = 2015)

my_car.hello()

Five Min Exercise

Make a class of your favorite movie or tv show
When the class is instantiated I want to be able to use the following methods
- .cast will return me a list of cast members real names
- .characters will return me a list of the characters in the movie
- .release will return me the release date of that movie
- .genre will return the genres this movie belongs to

Part 4 - Classes Terminology

Instantiate - when we instantiate a class we are creating a new instance of that class.
TheCar class is a blueprint. We instantiate it by creating a variable with the Car class.
This variable is now an instance of that care class
We can use the class over and over again, if we had multiple cars, or in the example of your previous exercise, multiple movies.

Part 5 - Instance and Class Variables

A class variable is a variable you want to be given to every instance of the class
A instance variable is specific to that instance of the class
The term self is used over and over again throughout class creation. This is referring to the object in that moment in time. (Instance of the object)

Five Min Exercise

Create a class called Athlete
Create three or more instances using that Athelete class
Every athlete has two legs, two arms, and is_rich(true)
Each athlete has THEIR OWN name, sport, team, height, weight

Part 6 - Scope

Scope works inside out
The methods and variables that are local will have access to those outside of it, however, the outside does not have access to the inside.
Think about Russian Nesting Dolls
return is what allows us to move values and variables between two different things

MISC

triple quotes doc string used to comment your code and help others read your code

Resources

Tutorials Point explanation of classes and objects - (http://www.tutorialspoint.com/python/python_classes_objects.htm)[http://www.tutorialspoint.com/python/python_classes_objects.htm]

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