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Python | Every Kth element removal in List

  • Last Updated : 19 Feb, 2020
Geek Week

We generally wish to employ a particular function to all the elements in a list. But sometimes, according to requirement we would wish to remove certain elements of the list, basically to every Kth element in list. Let’s discuss certain ways in which this can be performed.

Method #1 : Using list comprehension + enumerate()
The functionality of getting every Kth number of list can be done with the help of list comprehension and enumerate function helps in the iteration of the whole list.




# Python3 code to demonstrate
# Every Kth element removal in List
# using list comprehension + enumerate()
  
# initializing list 
test_list = [1, 4, 5, 6, 7, 8, 9, 12]
  
# printing the original list
print ("The original list is : " + str(test_list))
  
# initializing K 
K = 3
  
# using list comprehension + enumerate()
# Every Kth element removal in List
# Remove every third element
res = [i for j, i in enumerate(test_list) if j % K != 0]
  
# printing result
print ("The list after removing every Kth element : " + str(res))
Output :
The original list is : [1, 4, 5, 6, 7, 8, 9, 12]
The list after removing every kth element : [4, 5, 7, 8, 12]

 

Method #2 : Using list comprehension + list slicing
Above mentioned functions can help to perform these tasks. The list comprehension does the task of iteration in list and list slicing does the extraction of every Kth element.






# Python3 code to demonstrate
# Every Kth element removal in List
# using list comprehension + list slicing 
  
# initializing list 
test_list = [1, 4, 5, 6, 7, 8, 9, 12]
  
# printing the original list
print ("The original list is : " + str(test_list))
  
# initializing K 
K = 3
  
# using list comprehension + list slicing
# Every Kth element removal in List
# removes every 3rd element
res = [i for i in test_list if i not in test_list[0 :: 3]]
  
# printing result
print ("The list after removing every Kth element : " + str(res))
Output :
The original list is : [1, 4, 5, 6, 7, 8, 9, 12]
The list after removing every kth element : [4, 5, 7, 8, 12]

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