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Python | Print all the common elements of two lists
  • Difficulty Level : Easy
  • Last Updated : 05 Jun, 2020

Given two lists, print all the common element of two lists.

Examples:

Input : list1 = [1, 2, 3, 4, 5] 
        list2 = [5, 6, 7, 8, 9]
Output : {5}
Explanation: The common elements of 
both the lists are 3 and 4 

Input : list1 = [1, 2, 3, 4, 5] 
        list2 = [6, 7, 8, 9]
Output : No common elements 
Explanation: They do not have any 
elements in common in between them

Method 1:Using Set’s & property

Convert the lists to sets and then print set1&set2. set1&set2 returns the common elements set, where set1 is the list1 and set2 is the list2.



Below is the Python3 implementation of the above approach:




# Python program to find the common elements 
# in two lists
def common_member(a, b):
    a_set = set(a)
    b_set = set(b)
  
    if (a_set & b_set):
        print(a_set & b_set)
    else:
        print("No common elements"
           
   
a = [1, 2, 3, 4, 5]
b = [5, 6, 7, 8, 9]
common_member(a, b)
   
a = [1, 2, 3, 4, 5]
b = [6, 7, 8, 9]
common_member(a, b)


Output:

{5}
No common elements

Method 2:Using Set’s intersection property

Convert the list to set by conversion. Use intersection function to check if both sets have any elements in common. If they have any elements in common, then print the intersection of both the sets.

Below is the Python3 implementation of the above approach:




# Python program to find common elements in
# both sets using intersection function in
# sets
  
  
# function 
def common_member(a, b):    
    a_set = set(a)
    b_set = set(b)
      
    # check length 
    if len(a_set.intersection(b_set)) > 0:
        return(a_set.intersection(b_set))  
    else:
        return("no common elements")
      
   
a = [1, 2, 3, 4, 5]
b = [5, 6, 7, 8, 9]
print(common_member(a, b))
   
a =[1, 2, 3, 4, 5]
b =[6, 7, 8, 9]
print(common_member(a, b))


Output:

{5}
No common elements

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