# Adding K to each element in a Python list of integers

PythonServer Side ProgrammingProgramming

In data analysis, sometimes it becomes necessary to add some value to each element in a python list to judge about the outcome of a new scenario. This helps in testing the multiple scenarios on how the data set will behave with different values hence make a model or algorithms which can handle those scenarios. In this article, we will see how we can handle this requirement.

## Using List Comprehension

List comprehension is a normal way of handling the list where we loop through each element of the list. In the below example we add the same number to each element of the list using a simple for loop.

## Example

Live Demo

orig_list = [5, 6, 7, 4, 10]
print ("The given list is : " + str(orig_list))
# Use list comprehension
new_list = [n + 5 for n in orig_list]
# printing result
print ("After adding 5 to each element to list : " + str(new_list))

## Output

Running the above code gives us the following result −

The given list is : [5, 6, 7, 4, 10]
After adding 5 to each element to list : [10, 11, 12, 9, 15]

## Using lambda with map

The map and add method can also give us the same result. Lambda functions repeats the same action for affixed number of iterations and map is used to capture the result after all the lambda iterations are over.

## Example

Live Demo

orig_list = [5, 6, 7, 4, 10]
print ("The given list is : " + str(orig_list))
#Using map() + lambda
new_list= list(map(lambda m : m + 3, orig_list))
print ("After adding i to each element to list : " + str(new_list))

## Output

Running the above code gives us the following result −

The given list is : [5, 6, 7, 4, 10]
After adding i to each element to list : [8, 9, 10, 7, 13]

In place of the lambda operator, we can also use the add method along with map. In the below example, we create another list which has same number of elements as the length of the list and it contains the number which needs to be added. Then we apply the map method.

## Example

Live Demo

import operator
orig_list = [5, 6, 7, 4, 10]
print ("The given list is : " + str(orig_list))
# initializing new list
list_with_k_value = [9] * len(orig_list)
print ("After adding i2 to each element to list : " + str(new_list))
The given list is : [5, 6, 7, 4, 10]
After adding i2 to each element to list : [14, 15, 16, 13, 19]