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Python | Adding K to each element in a list of integers
  • Last Updated : 28 Jan, 2019

While working with the Python lists, we can come over a situation in which we require to add the integer k to each element in the list. We possibly need to iterate and add k to each element but that would increase the line of code. Let’s discuss certain shorthands to perform this task.

Method #1 : Using List Comprehension
List comprehension is just the short way to perform the task we perform using the naive method. This is mainly useful to save time and also is best among others when it comes to readability of the code.




# Python3 code to demonstrate 
# adding K to each element
# using list comprehension
  
# initializing list  
test_list = [4, 5, 6, 3, 9]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# initializing K
K = 4
  
# using list comprehension
# adding K to each element
res = [x + K for x in test_list]
  
# printing result 
print ("The list after adding K to each element : " +  str(res))

Output :

The original list is : [4, 5, 6, 3, 9]
The list after adding K to each element : [8, 9, 10, 7, 13]

Method #2 : Using map() + lambda
map function can be used to pair each element with the lambda function which performs the task of adding K to each element in the list.




# Python3 code to demonstrate 
# adding K to each element
# using map() + lambda
  
# initializing list  
test_list = [4, 5, 6, 3, 9]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# initializing K
K = 4
  
# using map() + lambda
# adding K to each element
res = list(map(lambda x : x + K, test_list))
  
# printing result 
print ("The list after adding K to each element : " +  str(res))

Output :



The original list is : [4, 5, 6, 3, 9]
The list after adding K to each element : [8, 9, 10, 7, 13]

Method #3 : Using map() + operator.add
This is similar to the above function but uses the operator.add to add each element to other element from the other list of K formed before applying the map function. It adds the similar index elements of list.




# Python3 code to demonstrate 
# adding K to each element
# using map() + operator.add
import operator
  
# initializing list  
test_list = [4, 5, 6, 3, 9]
  
# printing original list
print ("The original list is : " + str(test_list))
  
# initializing K list
K_list = [4] * len(test_list)
  
# using map() + operator.add
# adding K to each element
res = list(map(operator.add, test_list, K_list))
  
# printing result 
print ("The list after adding K to each element : " +  str(res))

Output :

The original list is : [4, 5, 6, 3, 9]
The list after adding K to each element : [8, 9, 10, 7, 13]

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