Question

Can anyone suggest a good solution to remove duplicates from nested lists if wanting to evaluate duplicates based on first element of each nested list?

The main list looks like this:

L = [['14', '65', 76], ['2', '5', 6], ['7', '12', 33], ['14', '22', 46]]

If there is another list with the same element at first position [k][0] that had already occurred, then I’d like to remove that list and get this result:

L = [['14', '65', 76], ['2', '5', 6], ['7', '12', 33]]

Can you suggest an algorithm to achieve this goal?

Answer 1

Do you care about preserving order / which duplicate is removed? If not, then:

dict((x[0], x) for x in L).values()

will do it. If you want to preserve order, and want to keep the first one you find then:

def unique_items(L):
    found = set()
    for item in L:
        if item[0] not in found:
            yield item
            found.add(item[0])

print list(unique_items(L))