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

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Context

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

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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]