beginning_python.py

import math

class cylinder(object):
    
    feature_type = "cylinder"

    def __init__(self, diameter, length):
        self.diameter = diameter
        self.length = length
        self._start_z = 0.00

    def volume(self):
        area = ((self.diameter / 2.0) ** 2) * math.pi
        volume = area * self.length
        return volume
    
    def end_z(self):
        return self._start_z + self.length


class shaft(object):

    def __init__(self):
        self.features = []
        
    def volume(self):
    
    	volume = 0.00
    	
    	for feature in self.features:
    		volume = volume + feature.volume()
    		
    	return volume

    def length(self):
    
    	length = 0
    	
    	for feature in self.features:
    		length = length + feature.length
    		
    	return length

    def add_feature(self, feature):	
        feature._start_z = self.length
        self.features.append(feature)

        
#-- Create some cylinder objects
c1 = cylinder(10.25, 1.25)
c2 = cylinder(8.25, 4.375)

s = shaft() #-- Create a new Shaft Objects

#-- Add cylinder objects to Shaft
s.add_feature(c1)
s.add_feature(c2)


print("Cylinder 1 Volume = %f   Start_z = %f" % (c1.volume(), c1._start_z()))
print("Cylinder 2 Volume = %f   Start_z = %f" % (c2.volume(), c2._start_z()))

#-- Display some info about the Shaft, which are derived from the Cylinder objects
#-- of which it is made of.
print("\nTotal Volume: %f cubic units" % s.volume())
print("\nOverall Length: %s" % s.length())