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Python | Count of common elements in the lists

  • Last Updated : 09 Sep, 2019

Sometimes, while working with Python list we can have a problem in which we have to compare two lists for index similarity and hence can have a task of counting equal index pairs. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using sum() + zip()
This task can be performed by passing the zip(), which performs task of mapping both list with each other, to the sum() which computes the sum according to equal indices.




# Python3 code to demonstrate working of
# Identical element summation in lists
# using sum() + zip()
  
# initialize lists
test_list1 = [5, 6, 10, 4, 7, 1, 19]
test_list2 = [6, 6, 10, 3, 7, 10, 19]
  
# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
  
# Identical element summation in lists
# using sum() + zip()
res = sum(x == y for x, y in zip(test_list1, test_list2))
  
# printing result
print("Summation of Identical elements : " + str(res))
Output :
The original list 1 is : [5, 6, 10, 4, 7, 1, 19]
The original list 2 is : [6, 6, 10, 3, 7, 10, 19]
Summation of Identical elements : 4

 

Method #2 : Using sum() + map() + eq
The task performed in above method using zip() can be executed here using the map function which performs similar task. The equality check can be performed by inbuilt eq operator.






# Python3 code to demonstrate working of
# Identical element summation in lists
# using sum() + map() + eq
from operator import eq
  
# initialize lists
test_list1 = [5, 6, 10, 4, 7, 1, 19]
test_list2 = [6, 6, 10, 3, 7, 10, 19]
  
# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))
  
# Identical element summation in lists
# using sum() + map() + eq
res = sum(map(eq, test_list1, test_list2))
  
# printing result
print("Summation of Identical elements : " + str(res))
Output :
The original list 1 is : [5, 6, 10, 4, 7, 1, 19]
The original list 2 is : [6, 6, 10, 3, 7, 10, 19]
Summation of Identical elements : 4

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