How Can I Remove Duplicate List Elements While Preserving Order in Python?

Removing Duplicates in a List While Maintaining Order

Removing duplicate elements from a list while preserving the original order can be challenging using a set, as it doesn't maintain the element sequence. This article explores several built-in and Pythonic idioms that address this issue.

Faster Option (f7 function)

The function f7 is the fastest option, and it iterates over the list while checking each element against a set to avoid duplication. However, it employs a trick to optimize performance: it assigns seen.add to a local variable seen_add to avoid repeatedly resolving the seen.add function call during each iteration. This enhances efficiency if the function is called frequently on the same dataset.

Ordered Set

An alternative solution is to use an ordered set, which maintains both uniqueness and insertion order. This approach offers a more efficient method for handling large datasets.

Additional Notes

• The or operator in the f7 function is used to attempt a set update.
• The seen.add() function always returns None, making the or expression redundant but logically correct.

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