Python: Add two given lists of different lengths, start from right, use itertools module

Last update on July 12 2025 13:08:54 (UTC/GMT +8 hours)

36. Add Lists from Right

Write a Python program to add two given lists of different lengths, starting from the right, using the itertools module.

Sample Solution:

Python Code:

from itertools import zip_longest

def elementswise_right_join(l1, l2):
    result = [a + b for a,b in zip_longest(reversed(l1), reversed(l2), fillvalue=0)][::-1]
    return result

nums1 = [2, 4, 7, 0, 5, 8]
nums2 = [3, 3, -1, 7]
print("\nOriginal lists:")
print(nums1)
print(nums2)
print("\nAdd said two lists from right:")
print(elementswise_right_join(nums1, nums2))

nums3 = [1, 2, 3, 4, 5, 6]
nums4 = [2, 4, -3]
print("\nOriginal lists:")
print(nums3)
print(nums4)
print("\nAdd said two lists from right:")
print(elementswise_right_join(nums3, nums4))

Sample Output:

Original lists:
[2, 4, 7, 0, 5, 8]
[3, 3, -1, 7]

Add said two lists from right:
[2, 4, 10, 3, 4, 15]

Original lists:
[1, 2, 3, 4, 5, 6]
[2, 4, -3]

Add said two lists from right:
[1, 2, 3, 6, 9, 3]

For more Practice: Solve these Related Problems:

• Write a Python program to add two lists of different lengths from the right side using itertools.zip_longest, padding missing values with zero.
• Write a Python program to sum two lists element-wise starting from the right and then reverse the resulting list.
• Write a Python program to create an iterator that aligns two lists from the right, adds corresponding elements, and then outputs the final list.
• Write a Python program to use itertools.zip_longest to add two lists from the right, applying a custom function for missing elements.

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Python Code Editor:

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