Python: Perform a deep flattens a list

Last update on April 19 2025 12:57:46 (UTC/GMT +8 hours)

Deep Flatten a List

Write a Python program to perform a deep flattening of a list.

Use recursion.
Use isinstance() with collections.abc.Iterable to check if an element is iterable.
If it is iterable, apply deep_flatten() recursively, otherwise return [lst].

Sample Solution:

Python Code:

from collections.abc import Iterable

# Define a function to deeply flatten a nested list.
def deep_flatten(lst):
    # Check if the input is an iterable (e.g., a list or nested list).
    if isinstance(lst, Iterable):
        # Use list comprehensions to recursively flatten nested lists.
        return [a for i in lst for a in deep_flatten(i)]
    else:
        # If the input is not an iterable, return a list containing the input element.
        return [lst]

# Example 1
nums = [1, [2], [[3], [4], 5], 6]
print("Original list elements:")
print(nums) 
print()
print("Deep flatten the said list:")
print(deep_flatten(nums))

# Example 2
nums = [[[1, 2, 3], [4, 5]], 6]
print("\nOriginal list elements:")
print(nums) 
print()
print("Deep flatten the said list:")
print(deep_flatten(nums))

Sample Output:

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

Deep flatten the said list:
[1, 2, 3, 4, 5, 6]

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

Deep flatten the said list:
[1, 2, 3, 4, 5, 6]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to deeply flatten a list that contains nested lists, tuples, and sets into a single flat list.
Write a Python program to flatten a nested list structure recursively, handling any depth of nesting.
Write a Python program to flatten a list with mixed types (e.g., dictionaries, lists) while preserving the order of numeric elements.
Write a Python program to perform a deep flatten of a list and then sort the resulting flat list in ascending order.

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