Python Membership and Identity Operators

• Difficulty Level : Easy
• Last Updated : 09 Aug, 2021

Membership Operators

Membership operators are operators used to validate the membership of a value. It tests for membership in a sequence, such as strings, lists, or tuples. 
 

• in operator: The ‘in’ operator is used to check if a value exists in a sequence or not. Evaluates to true if it finds a variable in the specified sequence and false otherwise.

• Python3

# Python program to illustrate

# Finding common member in list

# using 'in' operator

list1=[1,2,3,4,5]

list2=[6,7,8,9]

for item in list1:

    if item in list2:

        print("overlapping")     

else:

    print("not overlapping")

Output:

not overlapping

The same example without using in operator:

• Python3

# Python program to illustrate

# Finding common member in list

# without  using 'in' operator

#  Define a function() that takes two lists

def overlapping(list1,list2):

    c=0

    d=0

    for i in list1:

        c+=1

    for i in list2:

        d+=1

    for i in range(0,c):

        for j in range(0,d):

            if(list1[i]==list2[j]):

                return 1

     return 0

list1=[1,2,3,4,5]

list2=[6,7,8,9]

if(overlapping(list1,list2)):

    print("overlapping")

else:

    print("not overlapping")

Output:

not overlapping

• ‘not in’ operator- Evaluates to true if it does not finds a variable in the specified sequence and false otherwise. 

• Python3

# Python program to illustrate

# not 'in' operator

x = 24

y = 20

list = [10, 20, 30, 40, 50 ];

if ( x not in list ):

   print("x is NOT present in given list")

else:

   print("x is  present in given list")

if ( y in list ):

   print("y is present in given list")

else:

   print("y is NOT present in given list")

Identity operators

In Python identity operators are used to determine whether a value is of a certain class or type. They are usually used to determine the type of data a certain variable contains. 
There are different identity operators such as 

• ‘is’ operator – Evaluates to true if the variables on either side of the operator point to the same object and false otherwise. 

• Python3

# Python program to illustrate the use

# of 'is' identity operator

x = 5

if (type(x) is int):

    print("true")

else:

    print("false")

Output: 

true

• ‘is not’ operator – Evaluates to false if the variables on either side of the operator point to the same object and true otherwise. 

• Python3

# Python program to illustrate the

# use of 'is not' identity operator

x = 5.2

if (type(x) is not int):

    print("true")

else:

    print("false")

Output:

true