Python – Chunked interleave of Lists

Sometimes, while working with Lists, we can have a problem to perform merge operation. The simpler version is easy to implement. But when it comes to implement a variation of it, i.e the case in which we need to interleave in chunks alternatively, it becomes a tougher task. Let’s discuss certain way in which this task can be performed. 

Method : Using loop + extend() This task can be performed by using the above functionalities. In this, we compute the iterations required and then run a loop as many times. We add elements in list using extend() and variable number specified. 

Python3

# Python3 code to demonstrate
# Chunked interleave of Lists
# using loop + extend()

# Initializing lists
test_list1 = [4, 5, 6, 8, 10, 11]
test_list2 = [6, 7, 8, 9, 8, 12]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# Initializing step
step = 3

# Chunked interleave of Lists
# using loop + extend()
num = len(test_list1)
iters = int(num / step) + 1
res = []
for idx in range(iters):
    start = step * idx
    end = step * (idx + 1)
    res.extend(test_list1[start : end])
    res.extend(test_list2[start : end])

# printing result
print ("List after chunked merge : " + str(res))

Output : 

The original list 1 is : [4, 5, 6, 8, 10, 11]
The original list 2 is : [6, 7, 8, 9, 8, 12]
List after chunked merge : [4, 5, 6, 6, 7, 8, 8, 10, 11, 9, 8, 12]

Time Complexity: O(n*n) where n is the number of elements in the list “test_list”.  
Auxiliary Space: O(n), where n is the number of elements in the new res list