How Can I Remove Duplicates from a List While Maintaining Original Order in Python?

Handling Duplicates while Preserving List Order

When working with lists containing duplicate elements, it's often desirable to remove them while maintaining the original order. Using a set to achieve this, as it disregards the original sequence. However, Python offers several alternative approaches that preserve order while removing duplicates.

Built-in Functions and Pythonic Idioms

• Peter Be's Benchmark: https://www.peterbe.com/plog/uniqifiers-benchmark
• Fastest Solution:

def f7(seq):
    seen = set()
    seen_add = seen.add
    return [x for x in seq if not (x in seen or seen_add(x))]

This solution assigns seen.add to seen_add for efficiency, as calling seen.add repeatedly during loop iterations can introduce performance overhead due to Python's dynamic language nature.

• Ordered Set (Recipe): https://code.activestate.com/recipes/528878-ordered-set/

• Ordered Set Properties:

  • O(1) insertion, deletion, and member-check operations
• Note: Using an "or" after seen.add in the above code is simply a mechanism to attempt a set update, not an essential part of the logical test.

By utilizing these methods, developers can remove duplicate elements from lists without sacrificing the original order, catering to specific data manipulation scenarios.

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