Python - Incremental List Extension

Sometimes, while working with Python list, we can have a problem in which we need to extend a list in a very customized way. We may have to repeat contents of list and while doing that, each time new list must add a number to original list. This incremental expansion has applications in many domains. Let’s discuss a way in which this task can be performed.

Method : Using list comprehension
This task can be performed in a brute manner, but having a shorter implementation using list comprehension always is better. In this, we perform task in 2 steps, first we make a helper list to form a addition factor list and then cumulate the result using original list.

# Python3 code to demonstrate working of 
# Incremental List Extension 
# Using list comprehension 
  
# initializing list 
test_list = [7, 8, 9] 
  
# printing original list 
print("The original list is : " + str(test_list)) 
  
# Extension factor 
N = 4
  
# Addition factor  
M = 3
  
# Incremental List Extension 
# Using list comprehension 
temp = [1 * M**i for i in range(N)] 
temp[0] = 0
res = list([ele + tele for tele in temp for ele in test_list]) 
  
# printing result  
print("List after extension and addition : " + str(res)) 

Output :

The original list is : [7, 8, 9]
List after extension and addition : [7, 8, 9, 10, 11, 12, 16, 17, 18, 34, 35, 36]

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