AbstractClassEx.py

# need to import ABCMeta, abstractmethod from abc (abstract base classes) module to implement abstract class feature

from abc import ABCMeta, abstractmethod
# we required (metaclass = ABCMeta) to use feature of abstraction
class Shape(metaclass = ABCMeta):
#To tell python this is abstractmethod we have to use A decorator indicating abstract methods.
	@abstractmethod
	def area(self):
		pass
	
#now we will inherit Shape class in other concret class

class Circle(Shape):
	def __init__(self, radius):
		self.radius = radius
	def area(self):
		return self.radius**2 * 3.14
	
class Square(Shape):
	def __init__(self, side):
		self.side = side
	def area(self):
		return self.side * 2
	
class Rectangle(Shape):
	def __init__(self, length, breath):
		self.length = length
		self.breath = breath
	def area(self):
		return self.breath * self.length
	
circle = Circle(5)
square = Square(5)
rectangle = Rectangle(5,6)

print("area of circle is {}".format(circle.area()))
print("area of square is {}".format(square.area()))
print("area of rectngle is {}".format(rectangle.area()))

# Error

class ErrorClass(Shape):
	def errorPrint(self):
		print("This implementation give error since we are no implementing area method of abstarct class")
		
err = ErrorClass()
err.errorPrint()    

#output
#################################################################################################
#	area of circle is 78.5
#	area of square is 10
#	area of rectngle is 30
#	---------------------------------------------------------------------------
#	TypeError                                 Traceback (most recent call last)
#	<ipython-input-8-6aaa6b28b92e> in <module>()
#     44                 print("This implementation give error since we are no implementing area method of abstarct class")
#     45 
#	---> 46 err = ErrorClass()
#     47 err.errorPrint()
#
#	TypeError: Can't instantiate abstract class ErrorClass with abstract methods area
#######################################################################################################