Python Removing duplicates 3 at a time

Question

I am looking for some help here, I have a list which is exactly this

list like this: [1, 1, 1, 5, 5, 5, 10, 10, 10, 10, 10, 10, 8, 8, 8, 8, 8, 8]

wanted result: [1, 5, 10, 10, 8, 8]

I have tried every possible way by iterating through the list 3 at a time and replacing only every third.

''.join([List[i] for i in range(len(List) - 1) if List[i + 1] != XX[i]] + [List[-1]])

I just can't get my head around it is there some python wizard who can do this?

Thanks

In this case, a simple slice is all you need: `[1, 1, 1, 5, 5, 5, 10, 10, 10, 10, 10, 10, 8, 8, 8, 8, 8, 8][::3]`. — chepner, Oct 31 '16 at 13:38
Will there always be duplicates? What would `[1,2,3]` return? — Chris_Rands, Oct 31 '16 at 13:38
[1,1,1,1,1] does not exists and there are always 3 pairs of the same value — GabeTheApe, Oct 31 '16 at 13:39
nice oneliner - just nobody here who can read it at first sight. Did you really write it this way? — Matthias Burger, Oct 31 '16 at 13:39

score 7 · Answer 1 · edited May 23 '17 at 12:00

7

try

foo = [1, 1, 1, 5, 5, 5, 10, 10, 10, 10, 10, 10, 8, 8, 8, 8, 8, 8]
print foo[::3]

This is called "list slicing". What this practically does is it prints out every third argument of your list starting from the first. This article Explain Python's slice notation explains the concept more thoroughly.

edited May 23 '17 at 12:00

Community

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1

answered Oct 31 '16 at 13:40

Hannu

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that worked!! python is amazing Thanks – GabeTheApe Oct 31 '16 at 13:43
1

You could accept the answer if you are happy with it. Thanks. – Hannu Oct 31 '16 at 14:06

score 1 · Answer 2 · answered Oct 31 '16 at 13:45

Code:

lst    = [1, 1, 1, 5, 5, 5, 10, 10, 10, 10, 10, 10, 8, 8, 8, 8, 8, 8]
output = []

skip = 0
for idx, x in enumerate(lst):
    if skip:
        skip = skip - 1
        continue

    if (idx + 2) <= len(lst):
        if lst[idx] == lst[idx+1] and lst[idx] == lst[idx+2]:
            output.append(lst[idx])
            skip = skip + 2
    else:
        output.append(lst[idx])

print output

Python Removing duplicates 3 at a time

2 Answers2