1. VIII. INHERITANCE AND POLYMORPHISM
PYTHON PROGRAMMING
Engr. RANEL O. PADON

2. INHERITANCE

3. PYTHON PROGRAMMING TOPICS
I
•Introduction to Python Programming
II
•Python Basics
III
•Controlling the Program Flow
IV
•Program Components: Functions, Classes, Packages, and Modules
V
•Sequences (List and Tuples), and Dictionaries
VI
•Object-Based Programming: Classes and Objects
VII
•Customizing Classes and Operator Overloading
VIII
•Object-Oriented Programming: Inheritance and Polymorphism
IX
•Randomization Algorithms
X
•Exception Handling and Assertions
XI
•String Manipulation and Regular Expressions
XII
•File Handling and Processing
XIII
•GUI Programming Using Tkinter

4. INHERITANCE Background
Object-Based Programming
 programming using objects
Object-Oriented Programming
 programming using objects & hierarchies

5. INHERITANCE Background
Object-Oriented Programming
A family of classes is known as a class hierarchy.
As in a biological family, there are parent classes and child
classes.

6. INHERITANCE Background
Object-Oriented Programming
 the parent class is usually called base class or superclass
 the child class is known as a derived class or subclass

7. INHERITANCE Background
Object-Oriented Programming
Child classes can inherit data and methods from parent
classes, they can modify these data and methods, and they can
add their own data and methods.
The original class is still available and the separate child class is
small, since it does not need to repeat the code in the parent
class.

8. INHERITANCE Background
Object-Oriented Programming
The magic of object-oriented programming is that other parts of
the code do not need to distinguish whether an object is the
parent or the child – all generations in a family tree can be
treated as a unified object.

9. INHERITANCE Background
Object-Oriented Programming
In other words, one piece of code can work with all members
in a class family or hierarchy. This principle has revolutionized
the development of large computer systems.

10. INHERITANCE Reusing Attributes

11. INHERITANCE Reusing Attributes

12. INHERITANCE The Media Hierarchy

13. INHERITANCE Base and Derived Classes

14. INHERITANCE The CommunityMember Base Class

15. INHERITANCE The Shape Hierarchy

16. INHERITANCE Sample Implementation 1
Magulang
Anak

17. INHERITANCE Magulang Base Class
class Magulang:
def __init__(self, pangalan, kayamanan):
self.pangalan = pangalan
self.kayamanan = kayamanan

18. INHERITANCE Anak Derived Class
class Magulang:
def __init__(self, pangalan, kayamanan):
self.pangalan = pangalan
self.kayamanan = kayamanan
class Anak(Magulang):
def __init__(self, pangalan = "Juan Tamad", kayamanan = 1000000):
Magulang.__init__(self, pangalan, kayamanan)

19. INHERITANCE Sample Execution
class Magulang:
def __init__(self, pangalan, kayamanan):
self.pangalan = pangalan
self.kayamanan = kayamanan
class Anak(Magulang):
def __init__(self, pangalan, kayamanan):
Magulang.__init__(self, pangalan, kayamanan)
gorio = Anak("Mang Gorio", 1000000)
print gorio.pangalan
print gorio.kayamanan

20. INHERITANCE Anak with Default Args
class Magulang:
def __init__(self, pangalan, kayamanan):
self.pangalan = pangalan
self.kayamanan = kayamanan
class Anak(Magulang):
def __init__(self, pangalan = "Juan Tamad", kayamanan = 1000):
Magulang.__init__(self, pangalan, kayamanan)
print Anak().pangalan
print Anak().kayamanan

21. INHERITANCE Magulang with instance method
class Magulang:
def __init__(self, pangalan, kayamanan):
self.pangalan = pangalan
self.kayamanan = kayamanan
def getKayamanan(self):
return self.kayamanan
class Anak(Magulang):
def __init__(self, pangalan = "Juan Tamad", kayamanan = 1000):
Magulang.__init__(self, pangalan, kayamanan)
print Anak().pangalan
print Anak().getKayamanan()

22. INHERITANCE Sample Implementation 2
Rectangle
Square

23. INHERITANCE Rectangle Base Class
class Rectangle():
def __init__(self, lapad, haba):
self.lapad = lapad
self.haba = haba
def getArea(self):
return self.lapad*self.haba

24. INHERITANCE Square Derived Class
class Rectangle():
def __init__(self, lapad, haba):
self.lapad = lapad
self.haba = haba
def getArea(self):
return self.lapad*self.haba
class Square(Rectangle):
def __init__(self, lapad):
Rectangle.__init__(self, lapad, lapad)
def getArea(self):
return self.lapad**2

25. INHERITANCE Sample Execution
class Rectangle():
def __init__(self, lapad, haba):
self.lapad = lapad
self.haba = haba
def getArea(self):
return self.lapad*self.haba
class Square(Rectangle):
def __init__(self, lapad):
Rectangle.__init__(self, lapad, lapad)
def getArea(self):
return self.lapad**2
print Square(3).getArea()

26. INHERITANCE Deadly Diamond of Death
What would be the version of bite() that will be used by Hybrid?
Dark Side
Forces
Villains
attack()
Vampire
Vampire
bite()
Werewolf
bite()
Hybrid

27. INHERITANCE Deadly Diamond of Death
Dark Side
Forces
Villains
attack()
Vampire
Vampire
bite()
Python allow a limited form of multiple
inheritance hence care must be
observed to avoid name collisions or
ambiguity.
Werewolf
bite()
Hybrid
Other languages, like Java, do not allow
multiple inheritance.

28. INHERITANCE Polymorphism
Polymorphism is a consequence of inheritance. It is concept
wherein a name may denote instances of many different classes as
long as they are related by some common superclass.
It is the ability of one object, to appear as and be used like another
object.
In real life, a male person could behave polymorphically:
he could be a teacher, father, husband, son, etc depending on the
context of the situation or the persons he is interacting with.

29. INHERITANCE Polymorphism
Polymorphism is also applicable to systems with same base/core
components or systems interacting via unified interfaces.
 USB plug and play devices
 “.exe” files
 Linux kernel as used in various distributions
(Ubuntu, Fedora, Mint, Arch)
 Linux filesystems (in Linux everything is a file)
The beauty of it is that you could make small code changes
but it could be utilized by all objects inheriting or
interacting with it.

30. INHERITANCE Polymorphism

31. INHERITANCE Polymorphism
Hugis
Tatsulok
Bilog

32. INHERITANCE Polymorphism
class Hugis():
def __init__(self, pangalan):
self.pangalan = pangalan

33. INHERITANCE Polymorphism
class Hugis():
def __init__(self, pangalan):
self.pangalan = pangalan
class Tatsulok(Hugis):
def __init__(self, pangalan, pundasyon, taas):
Hugis.__init__(self, pangalan)
self.pundasyon = pundasyon
self.taas = taas
def getArea(self):
return 0.5*self.pundasyon*self.taas
print Tatsulok("Tatsulok sa Talipapa", 3, 4).getArea()

34. INHERITANCE Polymorphism
class Hugis():
def __init__(self, pangalan):
self.pangalan = pangalan
class Bilog(Hugis):
def __init__(self, pangalan, radyus):
Hugis.__init__(self, pangalan)
self.radyus = radyus
def getArea(self):
return 3.1416*self.radyus**2
print Bilog("Bilugang Mundo", 2).getArea()

35. INHERITANCE Polymorphism
class Hugis():
def __init__(self, pangalan):
class Tatsulok(Hugis):
def __init__(self, pangalan, pundasyon, taas):
def getArea(self):
class Bilog(Hugis):
def __init__(self, pangalan, radyus):
def getArea(self):
koleksyonNgHugis = []
koleksyonNgHugis += [Tatsulok("Tatsulok sa Talipapa", 3, 4)]
koleksyonNgHugis += [Bilog("Bilugang Mundo", 2)]
for i in range(len(koleksyonNgHugis)):
print koleksyonNgHugis[i].getArea()
POLYMORPHISM

36. INHERITANCE Polymorphism
Polymorphism is not the same as method overloading or
method overriding.
Polymorphism is only concerned with the application of
specific implementations to an interface or a more generic
base class.
Method overloading refers to methods that have the same
name but different signatures inside the same class.
Method overriding is where a subclass replaces the
implementation of one or more of its parent's methods.
Neither method overloading nor method overriding are by
themselves implementations of polymorphism.
http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Polymorphism_in_object-oriented_programming.html

37. INHERITANCE Abstract Class

38. INHERITANCE Abstract Class
 there are cases in which we define classes but we don’t
want to create any objects
 they are merely used as a base or model class
 abstract base classes are too generic to define real objects,
that is, they are abstract or no physical manifestation (it’s
like the idea of knowing how a dog looks like but not
knowing how an ‘animal’ looks like, and in this case,
‘animal’ is an abstract concept)

39. INHERITANCE Abstract Class
 Abstract class is a powerful idea since you only have to
communicate with the parent (abstract class), and all
classes implementing that parent class will follow
accordingly. It’s also related to the Polymorphism.

40. INHERITANCE Abstract Class
 ‘Shape’ is an abstract class. We don’t know how a ‘shape’
looks like, but we know that at a minimum it must have a
dimension or descriptor (name, length, width, height, radius,
color, rotation, etc). And these descriptors could be reused
or extended by its children.

41. INHERITANCE Abstract Class
 Abstract classes lay down the foundation/framework on
which their children could further extend.

42. INHERITANCE Abstract Class

43. INHERITANCE The Gaming Metaphor
Gameplay
MgaTauhan
KamponNgKadiliman
Manananggal
HalimawSaBanga
…
Menu Options
…
Maps
Tagapagligtas
Panday
MangJose

44. INHERITANCE Abstract Class
Abstract Classes
MgaTauhan
KamponNgKadiliman
Manananggal
HalimawSaBanga
Tagapagligtas
Panday
MangJose

45. INHERITANCE Abstract Class
class MgaTauhan():
def __init__(self, pangalan, buhay):
if self.__class__ == MgaTauhan:
raise NotImplementedError, "abstract class po ito!"
self.pangalan = pangalan
self.buhay = buhay
def draw(self):
raise NotImplementedError, "kelangang i-draw ito"

46. INHERITANCE Abstract Class
class KamponNgKadiliman(MgaTauhan):
bilang = 0
def __init__(self, pangalan):
MgaTauhan.__init__(self, pangalan, 50)
if self.__class__ == KamponNgKadiliman:
raise NotImplementedError, "abstract class lang po ito!"
KamponNgKadiliman.bilang += 1
def attack(self):
return 5
def __del__(self):
KamponNgKadiliman.bilang -= 1
self.isOutNumbered()
def isOutNumbered(self):
if KamponNgKadiliman.bilang == 1:
print “umatras ang mga HungHang"

47. INHERITANCE Abstract Class
class Tagapagligtas(MgaTauhan):
bilang = 0
def __init__(self, pangalan):
MgaTauhan.__init__(self, pangalan, 100)
if self.__class__ == Tagapagligtas:
raise NotImplementedError, "abstract class lang po ito!"
Tagapagligtas.bilang += 1
def attack(self):
return 10
def __del__(self):
Tagapagligtas.bilang -= 1
self.isOutNumbered()
def isOutNumbered(self):
if Tagapagligtas.bilang == 1:
“umatras ang ating Tagapagligtas"

48. INHERITANCE Abstract Class
class Manananggal(KamponNgKadiliman):
def __init__(self, pangalan):
KamponNgKadiliman.__init__(self, pangalan)
def draw(self):
return "loading Mananaggal.jpg.."
def kapangyarihan(self):
return "mystical na dila"

49. INHERITANCE Abstract Class
class HalimawSaBanga(KamponNgKadiliman):
def __init__(self, pangalan):
KamponNgKadiliman.__init__(self, pangalan)
def draw(self):
return "loading HalimawSaBanga.jpg.."
def kapangyarihan(self):
return "kagat at heavy-armored na banga"

50. INHERITANCE Abstract Class
class Panday(Tagapagligtas):
def __init__(self, pangalan):
Tagapagligtas.__init__(self, pangalan)
def draw(self):
return "loading Panday.jpg.."
def kapangyarihan(self):
return "titanium na espada, galvanized pa!"

51. INHERITANCE Abstract Class
class MangJose(Tagapagligtas):
def __init__(self, pangalan):
Tagapagligtas.__init__(self, pangalan)
def draw(self):
return "loading MangJose.jpg.."
def kapangyarihan(self):
return "CD-R King gadgets"

52. INHERITANCE Abstract Class
creatures
creatures
creatures
creatures
creatures
creatures
= []
+= [Manananggal("Taga-Caloocan")]
+= [HalimawSaBanga("Taga-Siquijor")]
+= [MangJose("Taga-KrusNaLigas")]
+= [MangJose("Taga-Cotabato")]
+= [Panday("Taga-Cubao Ilalim")]
for i in range(len(creatures)):
print creatures[i].draw()
print KamponNgKadiliman.bilang
print Tagapagligtas.bilang
del creatures[0]
loading Manananggal.jpg..
loading HalimawSaBanga.jpg..
loading MangJose.jpg..
loading MangJose.jpg..
loading Panday.jpg..
2
3
atras ang mga Hunghang!
This simple line is so powerful,
since it makes the current Creature
draw itself regardless of what
Creature it is!

53. INHERITANCE Flexibility and Power
Re-use, Improve, Extend

54. OOP: INHERITANCE is Powerful!

55. REFERENCES
 Deitel, Deitel, Liperi, and Wiedermann - Python: How to Program (2001).
 Disclaimer: Most of the images/information used here have no proper source citation, and I do
not claim ownership of these either. I don’t want to reinvent the wheel, and I just want to reuse
and reintegrate materials that I think are useful or cool, then present them in another light,
form, or perspective. Moreover, the images/information here are mainly used for
illustration/educational purposes only, in the spirit of openness of data, spreading light, and
empowering people with knowledge. 