CODEWITHSUNDEEP
python
Boby
Boby

Reputation: 79

Creating a list of unique items from a list of lists iteratively

I'm trying to create a list of unique items from a list of lists by selecting one item from each list, and if an item in a list is already in the unique item list, then select the second unique item and so on.See list and my attempt below;

mylist=`[[1,2,3],[1,2,3],[1,2,3]]`

def unique(lists):
    uniquelst=[]
    for _lst in lists:
        if _lst[0] not in uniquelst:
            uniquelst.append(_lst[0])
        else:
            uniquelst.append(_lst[1])

    return uniquelst

my output: [1, 2, 2]

Expected output: [1, 2, 3]

Only one item to be selected from each list, hence the appropriate solution should be able to produce the same result for this example [[1, 4, 3], [1, 2, 5], [1, 2, 3]] Any ideas? thanks.

Upvotes: 2

Views: 152

Answers (4)

kuro
kuro

Reputation: 3226

With the restrictions you mentioned this code should work - 

def unique(lists):
    uniquelst = []
    for lst in lists:
        for elem in lst:
            if elem not in uniquelst:
                uniquelst.append(elem)
                break

    return uniquelst

The second loop iterates over elements of the inner list and check if they are already present in uniquelst. In case they are not present, add the element and break from inner loop.

One thing I forgot to mention is that this code assumes the elements of inner list are in sorted order. If that is not the case, please sort inner list using sorted() or sort() before the second loop

Upvotes: 4

RomanPerekhrest
RomanPerekhrest

Reputation: 92854

With set object and itertools.chain(iterables) function:

import itertools

mylist = [[1,2,3],[1,2,3],[1,2,3]]
result = set(itertools.chain(*mylist))
print(list(result))

The output:

[1, 2, 3]

Upvotes: 5

Egor Biriukov
Egor Biriukov

Reputation: 679

flat_list = [item for sublist in mylist for item in sublist]
print(list(set(flat_list)))

Upvotes: 5

selten98
selten98

Reputation: 821

newlist = []
for l in mylist:
    newlist = newlist + l
return list(set(newlist))

Does this help you?

Upvotes: 1

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