Python: How to put unknow Multidimentional array in 1D array

Question

I want to know in python how to take a multidimensional array and put it in a 1D list. This thing work:

a = [[1,2],[3,4]]
sum(a,[])

I get this : [1,2,3,4]

But if I have a multidimensional with unknow dimension or not constant dimension like that :

a = [1,[3,4,[5,6,7]]]

How to get this : [1,2,3,4,5,6,7]

thanks

Possible Duplicate: http://stackoverflow.com/q/2158395/1907098 — Volatility, Jan 10 '13 at 02:26

score 3 · Answer 1 · edited May 23 '17 at 11:56

3

def flatten(lis):
    for i in lis:
        if isinstance(i, collections.Iterable) and not isinstance(i, basestring):
            for sub in flatten(i):
                yield sub
        else:
            yield i

Taken from Christian's solution on this question

If you want to return a list, you can use this:

def flatten(lis):
    flat_list = []
    for i in lis:
        if isinstance(i, collections.Iterable) and not isinstance(i, basestring):
            flat_list.extend(flatten(i))
        else:
            flat_list.append(i)
    return flat_list

However, for big lists, the generator function is much more efficient as it doesn't calculate the next value until it has too, unlike lists which stores its values in memory.

edited May 23 '17 at 11:56

Community

1
1

answered Jan 10 '13 at 02:35

Volatility

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+1 for showing a generator. The input can be arbitrarily large and this will perform well. – Peter Rowell Jan 10 '13 at 02:39
In my software (Blender ... use python3) ... I got this error with this kind of solution : "global name "collection" is not difined" – Jean-Francois Gallant Jan 10 '13 at 18:57
ops ... it's a module I missed to import. But now the error is about "basestring". – Jean-Francois Gallant Jan 10 '13 at 18:59
@Jean-FrancoisGallant You must be using Python 3. Use `str` instead of `basestring`. – Volatility Jan 10 '13 at 23:47

score 1 · Accepted Answer · answered Jan 10 '13 at 02:34

1

One way is to use recursion, something like this should work:

def flatten_list(l):
    new_l = []
    for item in l:
        if type(item) == type([]):
            new_l += flatten_list(item)
        else:
            new_l.append(item)
    return new_l

I did not test this code but the idea is there.

answered Jan 10 '13 at 02:34

Daniel Kuntz

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this one look like simple ! thanks ! And just because it's working as is without testing ! :) – Jean-Francois Gallant Jan 10 '13 at 18:30

Python: How to put unknow Multidimentional array in 1D array

2 Answers2