Remove all duplicate elements in a list

Question

I have a list (ex: [1, 2, 2, 3, 4, 3]) and I need to only keep the first occurrence of any of the elements in the list (ex: the list should become [1, 2 ,3, 4]). I know that I could do something like this:

badList = [1, 2, 2, 3, 4, 3]
goodList = []
for element in badList:
    if element in goodList:
        continue
    goodList.append(element)
print (goodList)

However, this is a very messy solution, and I am hoping there is a more elegant way.

Do you care about the order of elements? – pault Mar 26 '18 at 18:14 — pault, Mar 26 '18 at 18:14

score 2 · Accepted Answer · answered Mar 26 '18 at 18:14

2

from collections import OrderedDict
list(OrderedDict.fromkeys(badList))
[1, 2, 3, 4]

credit to @poke

answered Mar 26 '18 at 18:14

Peter Dolan

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score 0 · Answer 2 · answered Mar 26 '18 at 18:13

0

Just convert to a set then back to a list:

goodList = list(set(badList))

answered Mar 26 '18 at 18:13

Adriano Martins

1,788
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This doesn't keep order which OP indicated he cared about – Peter Dolan Mar 26 '18 at 18:14
The order could be kept this way: `goodList = sorted(list(set(badList)))` – Jānis Š. Mar 26 '18 at 18:25

Remove all duplicate elements in a list

2 Answers2