(continued from previous pageself radiusself metal etc are the instance variable which must be unique ""self date date self metal metal self radius radius self price price self quantity quantity def cost(self)return self price self quantity def area(self)return math pi self radius** object of class let' create an object 'rof the class 'ring'to verify the operation of the classas shown belowfrom pythonic import ring ring(" = - ""gold" metal 'goldr cost( area( class variable and initialization letsadd some class variables to the above class and define some initial values to the arguments in the __init__ function as shown belownoteclass variable should be used to create the shared variables it is always good to put the shared variables on the class level rather than instance level pythonic py import math import time class ring(object)""here we will see the actual logic behind various pieces of python language instancesvariablesmethod and @property etc alsowe will see the combine usage of these pieces to complete design with agile methodology ""class variables date time strftime("% -% -% "time gmtime()today' date "yyyy-mm-ddcenter center of the ring def __init__(selfdate=datemetal="copper"radius= price= quantity= )(continues on next page simple data structure to classes