#!/usr/bin/env python

# Written by: DGC

import abc

#==============================================================================

class Shape(object):

__metaclass__ = abc.ABCMeta

@abc.abstractmethod

def __init__(self):

pass

def area(self):

"""

Returns the area of the shape calculated using the shape specific

implementation.

"""

assert self.calculator != None, "self.calculator not defined."

return self.calculator(self)

#==============================================================================

class Rectangle(Shape):

def __init__(self, x, y):

self.calculator = rectangular_area_calculator

self.x = x

self.y = y

#==============================================================================

def rectangular_area_calculator(rectangle):

return rectangle.x * rectangle.y

#==============================================================================

class Triangle(Shape):

def __init__(self, base, height):

self.calculator = triangular_area_calculator

self.base = base

self.height = height

#==============================================================================

def triangular_area_calculator(triangle):

return 0.5 * triangle.base * triangle.height

#==============================================================================

if (__name__ == "__main__"):

x = 4

y = 5

rect = Rectangle(x, y)

print(str(x) + " x " + str(y) + " Rectangle area: " + str(rect.area()))

base = 4

height = 5

tri = Triangle(base, height);

print(

"Base " +

str(base) +

", Height " +

str(height) +

" Triangle area: " +

str(tri.area())

)