Flatten Nested List in Python

Recursively flatten a deeply nested list into a single list.

An Nguyễn VănAn Nguyễn Văn
November 10, 2025
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Code

1def flatten(lst):
2    result = []
3    for i in lst:
4        if isinstance(i, list):
5            result.extend(flatten(i))
6        else:
7            result.append(i)
8    return result
9
10print(flatten([1, [2, [3, 4]], 5]))
11

Time Complexity Analysis

O(1)Estimated time complexity

This is an automated analysis. The actual complexity may vary based on implementation details.

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An Nguyễn Văn

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