How can you remove duplicate values from a list?

To remove duplicates while preserving order, you can use a set to track seen items and build a new list. Example:

def remove_duplicates(lst):
    seen = set()
    result = []
    for item in lst:
        if item not in seen:
            seen.add(item)
            result.append(item)
    return result

This runs in O(n) time and O(n) space. If order is not important, you can simply convert to a set: list(set(lst)), which is also O(n) but may reorder elements. For stable ordering with Python 3.7+, dict.fromkeys(lst) or list(dict.fromkeys(lst)) achieves the same effect with O(n) complexity.