Python Membership and Identity Operators

Difficulty Level : Easy
Last Updated : 03 Dec, 2020

Membership Operators

Membership operators are operators used to validate the membership of a value. It test 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.

# 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

Same example without using in operator:

# 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.

# 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 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.

# 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.

# 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
```

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