remove curly brackets from a list of sets in python

Question

my code looks something like this:

documents=set()
finals = []
temporary_set= set()
temporary_set.add(i)
finals.append(documents.intersection(temporary_set))

when i want to get all values from the finals list i use:

for final in finals:
    print (final)

This returns however the items as a set item within a list. like this:

[{27309053}, {23625724}, {25051134}]

How can i make it that the curly brackets will be omitted and that my result will look like this:

[27309053, 23625724, 25051134]

???

score 4 · Accepted Answer · answered Nov 08 '18 at 18:02

4

You can change

finals.append(documents.intersection(temporary_set))

to

finals.extend(documents.intersection(temporary_set))

which will add each element of that intersection to the list, rather than the intersection itself.

answered Nov 08 '18 at 18:02

Patrick Haugh

Great! this was exactly the answer I was looking for. Thanks a lot! – Jorian Onderwater Nov 08 '18 at 18:09

score 2 · Answer 2 · answered Nov 08 '18 at 17:58

2

You can flatten your list of sets using itertools.chain.from_iterable:

import itertools

x = [{27309053}, {23625724}, {25051134}]

list(itertools.chain.from_iterable(x))
# [27309053, 23625724, 25051134]

answered Nov 08 '18 at 17:58

sacuL

1

they could but it would better to go back a step on not create a list of sets in the first place – Chris_Rands Nov 08 '18 at 18:00
I agree. But the question was essentially that they end up with a list of sets, and want it turned into a flat list... – sacuL Nov 08 '18 at 18:01
1

if you intupret the question that way, then it's a common duplicate https://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python (Patrick's approach is better IMO) – Chris_Rands Nov 08 '18 at 18:02

timgeb · Answer 3 · 2018-11-08T18:38:52.570

1

Fixing the code upstream by using extend is the way to go here.

If you end up with a list

l = [{27309053}, {23625724}, {25051134}]

where you can't modify how it's created, you can use iterable unpacking like this:

>>> l = [{27309053}, {23625724}, {25051134}]
>>> [x for x, in l]
>>> [27309053, 23625724, 25051134]

edited Nov 08 '18 at 18:38

answered Nov 08 '18 at 18:08

timgeb

1

Better: `[x for [x] in l]` (non-destructive, and validates sets are 1 item only) – wim Nov 08 '18 at 18:33
@wim Good idea, I modified my answer with the tuple version of this. – timgeb Nov 08 '18 at 18:39

score 0 · Answer 4 · answered Nov 08 '18 at 17:59

0

l = [{27309053}, {23625724}, {25051134}]

[x for sl in l for x in sl]  # evaluates to [27309053, 23625724, 25051134]

answered Nov 08 '18 at 17:59

Alex

4 Answers4