Polymorphism.pptx

POLYMORPHISM
Poly means many. Morphs means forms.
Polymorphism means 'Many Forms'.
Eg1: Yourself is best example of polymorphism.In front of Your parents You will have one
type of behaviour and with friends another type of behaviour.Same person but different
behaviours at different places,which is nothing but polymorphism.
Eg2: + operator acts as concatenation and arithmetic addition
Eg3: * operator acts as multiplication and repetition operator
Eg4: The Same method with different implementations in Parent class and child
classes.(overriding)
Related to polymorphism the following 4 topics are important
1. Duck Typing Philosophy of Python
2. Overloading
1. Operator Overloading
2. Method Overloading
3. Constructor Overloading
1. Duck Typing Philosophy of Python:
In Python we cannot specify the type explicitly. Based on provided value at runtime the type
will be considered automatically. Hence Python is considered as Dynamically Typed
Programming Language.

def f1(obj):
obj.talk()
What is the type of obj? We cannot decide at the beginning. At runtime we can pass any
type.Then how we can decide the type?
At runtime if 'it walks like a duck and talks like a duck,it must be duck'. Python follows this
principle. This is called Duck Typing Philosophy of Python.
Demo Program:
1) class Duck:
2) def talk(self):
3) print('Quack.. Quack..')
4)
5) class Dog:
6) def talk(self):
7) print('Bow Bow..')
8)
9) class Cat:
10) def talk(self):
11) print('Moew Moew ..')

12)
13) class Goat:
14) def talk(self):
15) print('Myaah Myaah ..')
16)
17) def f1(obj):
18) obj.talk()
19)
20) l=[Duck(),Cat(),Dog(),Goat()]
21) for obj in l:
22) f1(obj)
Output:
Quack.. Quack..
Moew Moew ..
Bow Bow..
Myaah Myaah ..
The problem in this approach is if obj does not contain talk() method then we will get
AttributeError
Eg:
1) class Duck:
2) def talk(self):

5) class Dog:
6) def bark(self):
8) def f1(obj):
9) obj.talk()
10)
11) d=Duck()
12) f1(d)
14) d=Dog()
15) f1(d)
Output:
D:kiran_classes>py test.py
Quack.. Quack..
Traceback (most recent call last):
File "test.py", line 22, in <module>
f1(d)
File "test.py", line 13, in f1
obj.talk()
AttributeError: 'Dog' object has no attribute 'talk'
But we can solve this problem by using hasattr() function.
hasattr(obj,'attributename')
attributename can be method name or variable name

Demo Program with hasattr() function:
1) class Duck:
2) def talk(self):
4)
5) class Human:
6) def talk(self):
7) print('Hello Hi...')
8)
9) class Dog:
10) def bark(self):
12)
13) def f1(obj):
14) if hasattr(obj,'talk'):
15) obj.talk()
16) elif hasattr(obj,'bark'):
17) obj.bark()
18)
19) d=Duck()
20) f1(d)
21)
22) h=Human()
23) f1(h)

24)
25) d=Dog()
26) f1(d)
27) Myaah Myaah Myaah...
Overloading:
We can use same operator or methods for different purposes.
Eg1: + operator can be used for Arithmetic addition and String concatenation
print(10+20)#30
print('kiran'+'soft')#kiransoft
Eg2: * operator can be used for multiplication and string repetition purposes.
print(10*20)#200
print('kiran'*3)#kirankirankiran
Eg3: We can use deposit() method to deposit cash or cheque or dd
deposit(cash)
deposit(cheque)
deposit(dd)
There are 3 types of overloading
1. Operator Overloading
2. Method Overloading
3. Constructor Overloading

1. Operator Overloading:
We can use the same operator for multiple purposes, which is nothing but operator
overloading.
Python supports operator overloading.
Eg1: + operator can be used for Arithmetic addition and String concatenation
print(10+20)#30
print('kiran'+'soft')#kiransoft
Eg2: * operator can be used for multiplication and string repetition purposes.
print(10*20)#200
print('kiran'*3)#kirankirankiran
Demo program to use + operator for our class objects:
1) class Book:
2) def __init__(self,pages):
3) self.pages=pages
4)
5) b1=Book(100)
6) b2=Book(200)
7) print(b1+b2)
D:kiran_classes>py test.py
Traceback (most recent call last):
File "test.py", line 7, in <module>
print(b1+b2)

TypeError: unsupported operand type(s) for +: 'Book' and 'Book'
We can overload + operator to work with Book objects also. i.e Python supports Operator
Overloading.
For every operator Magic Methods are available. To overload any operator we have to
override that Method in our class.
Internally + operator is implemented by using __add__() method.This method is called magic
method for + operator. We have to override this method in our class.
Demo program to overload + operator for our Book class objects:
1) class Book:
2) def __init__(self,pages):
3) self.pages=pages
4)
5) def __add__(self,other):
6) return self.pages+other.pages
7)
8) b1=Book(100)
9) b2=Book(200)
10) print('The Total Number of Pages:',b1+b2)

Output: The Total Number of Pages: 300
The following is the list of operators and corresponding magic methods.
+ ---> object.__add__(self,other)
- ---> object.__sub__(self,other)
* ---> object.__mul__(self,other)
/ ---> object.__div__(self,other)
// ---> object.__floordiv__(self,other)
% ---> object.__mod__(self,other)
** ---> object.__pow__(self,other)
+= ---> object.__iadd__(self,other)
-= ---> object.__isub__(self,other)
*= ---> object.__imul__(self,other)
/= ---> object.__idiv__(self,other)
//= ---> object.__ifloordiv__(self,other)
%= ---> object.__imod__(self,other)
**= ---> object.__ipow__(self,other)
< ---> object.__lt__(self,other)
<= ---> object.__le__(self,other)
> ---> object.__gt__(self,other)
>= ---> object.__ge__(self,other)
== ---> object.__eq__(self,other)
!= ---> object.__ne__(self,other)
Overloading > and <= operators for Student class objects:

1) class Student:
2) def __init__(self,name,marks):
3) self.name=name
4) self.marks=marks
5) def __gt__(self,other):
6) return self.marks>other.marks
7) def __le__(self,other):
8) return self.marks<=other.marks
9)
10)
11) print("10>20 =",10>20)
12) s1=Student("kiran",100)
13) s2=Student("Ravi",200)
14) print("s1>s2=",s1>s2)
15) print("s1<s2=",s1<s2)
16) print("s1<=s2=",s1<=s2)
17) print("s1>=s2=",s1>=s2)
Output:
10>20 = False
s1>s2= False
s1<s2= True
s1<=s2= True
s1>=s2= False

Program to overload multiplication operator to work on Employee objects:
1) class Employee:
2) def __init__(self,name,salary):
3) self.name=name
4) self.salary=salary
5) def __mul__(self,other):
6) return self.salary*other.days
7)
8) class TimeSheet:
9) def __init__(self,name,days):
10) self.name=name
11) self.days=days
12)
13) e=Employee('kiran',500)
14) t=TimeSheet('kiran',25)
15) print('This Month Salary:',e*t)
Output: This Month Salary: 12500
2. Method Overloading:
If 2 methods having same name but different type of arguments then those methods are
said to
be overloaded methods.
Eg: m1(int a)
m1(double d)

But in Python Method overloading is not possible.
If we are trying to declare multiple methods with same name and different number of
arguments then Python will always consider only last method.
Demo Program:
1) class Test:
2) def m1(self):
3) print('no-arg method')
4) def m1(self,a):
5) print('one-arg method')
6) def m1(self,a,b):
7) print('two-arg method')
8)
9) t=Test()
10) #t.m1()
11) #t.m1(10)
12) t.m1(10,20)
Output: two-arg method
In the above program python will consider only last method.
How we can handle overloaded method requirements in Python:
Most of the times, if method with variable number of arguments required then we can
handle with default arguments or with variable number of argument methods.

Demo Program with Default Arguments:
1) class Test:
2) def sum(self,a=None,b=None,c=None):
3) if a!=None and b!= None and c!= None:
4) print('The Sum of 3 Numbers:',a+b+c)
5) elif a!=None and b!= None:
6) print('The Sum of 2 Numbers:',a+b)
7) else:
8) print('Please provide 2 or 3 arguments')
9)
10) t=Test()
11) t.sum(10,20)
12) t.sum(10,20,30)
13) t.sum(10)
Output:
The Sum of 2 Numbers: 30
The Sum of 3 Numbers: 60
Please provide 2 or 3 arguments
Demo Program with Variable Number of Arguments:

1) class Test:
2) def sum(self,*a):
3) total=0
4) for x in a:
5) total=total+x
6) print('The Sum:',total)
7)
8)
9) t=Test()
10) t.sum(10,20)
11) t.sum(10,20,30)
12) t.sum(10)
13) t.sum()
3. Constructor Overloading:
Constructor overloading is not possible in Python.
If we define multiple constructors then the last constructor will be considered.
1) class Test:
2) def __init__(self):
3) print('No-Arg Constructor')
4)
5) def __init__(self,a):
6) print('One-Arg constructor')
7)

8) def __init__(self,a,b):
9) print('Two-Arg constructor')
10) #t1=Test()
11) #t1=Test(10)
12) t1=Test(10,20)
Output: Two-Arg constructor
In the above program only Two-Arg Constructor is available.
But based on our requirement we can declare constructor with default arguments and
variable number of arguments.
Constructor with Default Arguments:
1) class Test:
2) def __init__(self,a=None,b=None,c=None):
3) print('Constructor with 0|1|2|3 number of arguments')
4)
5) t1=Test()
6) t2=Test(10)
7) t3=Test(10,20)
8) t4=Test(10,20,30)

Output:
Constructor with 0|1|2|3 number of arguments
Constructor with Variable Number of Arguments:
1) class Test:
2) def __init__(self,*a):
3) print('Constructor with variable number of arguments')
4)
5) t1=Test()
6) t2=Test(10)
7) t3=Test(10,20)
8) t4=Test(10,20,30)
9) t5=Test(10,20,30,40,50,60)
Output:
Constructor with variable number of arguments

Method overriding:
What ever members available in the parent class are bydefault available to the child class
through inheritance. If the child class not satisfied with parent class implementation then
child class is allowed to redefine that method in the child class based on its requirement.
This concept is called overriding.
Overriding concept applicable for both methods and constructors.
Demo Program for Method overriding:
1) class P:
2) def property(self):
3) print('Gold+Land+Cash+Power')
4) def marry(self):
5) print('Appalamma')
6) class C(P):
7) def marry(self):
8) print('Katrina Kaif')
9)
10) c=C()
11) c.property()
12) c.marry()
Output:
Gold+Land+Cash+Power
Katrina Kaif

From Overriding method of child class,we can call parent class method also by using
super()
method.
1) class P:
2) def property(self):
3) print('Gold+Land+Cash+Power')
4) def marry(self):
5) print('Appalamma')
6) class C(P):
7) def marry(self):
8) super().marry()
9) print('Katrina Kaif')
10)
11) c=C()
12) c.property()
13) c.marry()
Output:
Gold+Land+Cash+Power
Appalamma
Katrina Kaif

Demo Program for Constructor overriding:
1) class P:
3) print('Parent Constructor')
4)
5) class C(P):
7) print('Child Constructor')
8)
9) c=C()
Output: Child Constructor
In the above example,if child class does not contain constructor then parent class
constructor will be executed From child class constuctor we can call parent class
constructor by using super() method.
Demo Program to call Parent class constructor by using super():
1) class Person:
2) def __init__(self,name,age):
3) self.name=name
4) self.age=age
5)
6) class Employee(Person):
7) def __init__(self,name,age,eno,esal):
8) super().__init__(name,age)

9) self.eno=eno
10) self.esal=esal
11)
12) def display(self):
13) print('Employee Name:',self.name)
14) print('Employee Age:',self.age)
15) print('Employee Number:',self.eno)
16) print('Employee Salary:',self.esal)
17)
18) e1=Employee('Durga',48,872425,26000)
19) e1.display()
20) e2=Employee('Sunny',39,872426,36000)
21) e2.display()
Output:
Employee Name: Durga
Employee Age: 48
Employee Number: 872425
Employee Salary: 26000
Employee Name: Sunny
Employee Age: 39
Employee Number: 872426
Employee Salary: 36000

Polymorphism.pptx

More Related Content

Similar to Polymorphism.pptx

Recently uploaded

Polymorphism.pptx