Python: Flatten a shallow list

Last update on April 19 2025 13:02:41 (UTC/GMT +8 hours)

Flatten Shallow List

Write a Python program to flatten a shallow list.

Example - 1 :

Example - 2 :

Example - 3 :

Sample Solution-1:

Python Code:

# Import the 'itertools' module, which provides various functions for working with iterators
import itertools

# Define a list 'original_list' containing nested sublists
original_list = [[2, 4, 3], [1, 5, 6], [9], [7, 9, 0]]

# Use 'itertools.chain' and the unpacking operator (*) to merge the sublists into a single flat list
new_merged_list = list(itertools.chain(*original_list))

# Print the newly merged list 'new_merged_list'
print(new_merged_list)

Sample Output:

[2, 4, 3, 1, 5, 6, 9, 7, 9, 0]

Sample Solution-2:

Use a list comprehension to extract each value from sub-lists in order.

Python Code:

# Define a function named 'flatten' that takes a list of lists 'nums' and flattens it into a single list
def flatten(nums):
    # Use a list comprehension to iterate through the sublists 'y' and the elements 'x' within each sublist
    return [x for y in nums for x in y]

# Define a list 'nums' containing nested sublists
nums = [[1, 2, 3, 4], [5, 6, 7, 8]
print("Original list elements:")
# Print the original list 'nums'
print(nums)

# Print a newline for separation
print("\nFlatten the said list:")
# Call the 'flatten' function to flatten the 'nums' list and print the result
print(flatten(nums)

# Reassign 'nums' with a different list of nested sublists
nums = [[2, 4, 3], [1, 5, 6], [9], [7, 9, 0]]
print("\nOriginal list elements:")
# Print the original list 'nums'
print(nums)

# Print a newline for separation
print("\nFlatten the said list:")
# Call the 'flatten' function to flatten the new 'nums' list and print the result
print(flatten(nums))

Sample Output:

Original list elements:
[[1, 2, 3, 4], [5, 6, 7, 8]]

Flatten the said list:
[1, 2, 3, 4, 5, 6, 7, 8]

Original list elements:
[[2, 4, 3], [1, 5, 6], [9], [7, 9, 0]]

Flatten the said list:
[2, 4, 3, 1, 5, 6, 9, 7, 9, 0]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to flatten a deeply nested list.
Write a Python program to flatten a list of lists where some elements are not lists.
Write a Python program to flatten a list and remove duplicates simultaneously.
Write a Python program to flatten a list and maintain the original order of unique elements.

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