Classes Attributes vs Object Attributes

Class Attributes

class Vehicle:
	
	color = 'red' # This should not be changed
	engine = 'v6' # Should be static and should not be changed
 	
	def __init__(self, body_type, make):
		self.vehicle_body = body_type
		self.vehicle_make = make
		

!!! BAD PRACTICE TO CHANGE THE CLASS ATTRIBUTES !!!

# To change the color from the Class above, which you should not do:

Vehicle.color = 'green'

• This becomes a design problem as there are thousands of lines of code in a program.

!!! THIS IS ALSO A BAD PRACTICE !!! :

Instance Variable

car1 = Vehicle('suv', 'toyota')

# By changing the color for the car1 instance
# This changes the color just for the car1 instance
car1.color = 'purple'

# The class does not have a engine variable but by assigining it, you are creating an instance variable called v6 for car1. 
# The rest of the cars do not have an engine attribute
car1.engine = 'v6'

• This also becomes a design issue as other developers can assign car instances willy nilly making this an issue

• Makes interpreting the code hard

Overview Recap:

class Vehicle:
	# The varialbe should not be changed outside of the class specification
	# This is a class attribute
	vehicle_counter = 0
 	
	# This method will always run
	def __init__(self, body_type, make):
		self.vehicle_body = body_type
		self.vehicle_make = make
	
	# Returning a class attribute should be associated with the class
	# Should not be associated with the instance (self)
	def get_vehicle_count(self):
		return Vehicle.vehicle_counter
		
		# This increments the Class value and is not instance related
		Vehicle.vehicle_counter += 1