flatten list in python

Question

I want to flatten the list:

exampleArray = [[[151.68694121866872]], 
                [[101.59534468349297]], 
                [[72.16055999176308]]]

to:

[151.68694121866872, 101.59534468349297, 72.16055999176308]

Right now I am doing this:

resultArray= list(chain.from_iterable(list(chain.from_iterable(exampleArray))))

Even though it works I wanted to know if there's a better way.

It is [`itertools.chain.from_iterable`](http://docs.python.org/library/itertools.html#itertools.chain.from_iterable). — Dan D., Oct 15 '12 at 09:53
I guess then just `list(chain.from_iterable(chain.from_iterable(lis)))` is enough, no need of that `list()` call. ` — Ashwini Chaudhary, Oct 15 '12 at 09:57
is it always just a list containing single element (nested) sublists? — moooeeeep, Oct 15 '12 at 09:57
This is very close: [Flatten (an irregular) list of lists in Python](http://stackoverflow.com/a/2158532/63011) — Paolo Moretti, Oct 15 '12 at 10:01

score 2 · Accepted Answer · answered Oct 15 '12 at 09:51

2

How about

result = [x[0][0] for x in exampleArray]

answered Oct 15 '12 at 09:51

waitingkuo

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Very good specific example. Not the best general one though, obviously. – Tim McNamara Oct 15 '12 at 10:01

score 1 · Answer 2 · answered Oct 15 '12 at 09:52

1

In [6]: from itertools import chain

In [7]: lis=[[[151.68694121866872]], [[101.59534468349297]], [[72.16055999176308]]]

In [8]: list(chain(*(chain(*lis))))

Out[8]: [151.68694121866872, 101.59534468349297, 72.16055999176308]

answered Oct 15 '12 at 09:52

Ashwini Chaudhary

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Meitham · Answer 3 · 2016-06-29T09:58:09.700

1

There isn't a better way, this is the most recommended way. See official recipes

def flatten(listOfLists):
    "Flatten one level of nesting"
    return chain.from_iterable(listOfLists)

edited Jun 29 '16 at 09:58

answered Oct 15 '12 at 09:52

Meitham

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thanks just wanted to see if there was will remove the extra list I added to the code – user1741339 Oct 15 '12 at 10:57

score 1 · Answer 4 · answered Oct 15 '12 at 09:59

You don't need to convert the itertools.chain object (an iterable) into a list:

resultArray= list(chain.from_iterable(list(chain.from_iterable(exampleArray))))
# could be rewritten as
resultArray= list(chain.from_iterable(chain.from_iterable(exampleArray)))

.

You could write a deepness function using recursion:

def deep_chain_from_iterable(it, n):
    if n == 0:
        return list(it)
    else:
        return deep_chain_from_iterable(itertools.chain.from_iterable(it),n-1)

deep_chain_from_iterable(exampleArray, 2)

score 0 · Answer 5 · answered Oct 15 '12 at 11:56

0

For fixed level of depth (as in example) you can just sum enough times:

sum(sum(listoflistsoflists, []), [])

answered Oct 15 '12 at 11:56

mechmind

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flatten list in python

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