Unpack series of tuples and lists into 1-d list?

Question

I am trying to create a array from three kind of lists. Like l1, l2, l3. I am getting error says float is not iterable. How to unpack these lists into a 1-d list in python?

l1=[(260.3, 185.0), (268.01, 499.16)]
l2=[(268.01, 500.87), (678.9, 506.0)]
l3=((149.86, 354.48), (182.39, 344.2))
def unpack_lines(l1, l2, l3):
    out = []
    out.extend(l1[0][0])
    out.extend(l1[0][1])
    out.extend(l1[1][0])
    out.extend(l1[1][1])
    out.extend(l2[0][0])
    out.extend(l2[0][1])
    out.extend(l2[1][0])
    out.extend(l2[1][1])
    out.extend(l3[0][0])
    out.extend(l3[0][1])
    out.extend(l3[1][0])
    out.extend(l3[1][1])
    return out

unpack_lines(l1, l2, l3)

Error

TypeError                                 Traceback (most recent call last)
<ipython-input-27-6f84bf5b956a> in <module>
----> 1 unpack_lines(l1, l2, l3)

<ipython-input-26-159b13d00464> in unpack_lines(l1, l2, l3)
      1 def unpack_lines(l1, l2, l3):
      2     out = []
----> 3     out.extend(l1[0][0])
      4     out.extend(l1[0][1])
      5     out.extend(l1[1][0])

TypeError: 'float' object is not iterable

Expected output

[260.3,
185.0,
 268.01,
 499.16,
 268.01,
 500.87,
 678.9,
 506.0,
 149.86,
 354.48,
 182.39,
 344.2]

`return list(itertools.chain.from_iterable(itertools.chain(l1, l2, l3)))` — han solo, Aug 22 '20 at 18:09
`extend` takes an iterable. You probably meant `append`, or `extend(list[i])` — wjandrea, Aug 22 '20 at 18:10
I wanted 1-D array for numpy, so i did extend - something like this I am trying - `[a, b, c, d, e, f, ..... ]` — ajayramesh, Aug 22 '20 at 18:12
Does this answer your question? [How to make a flat list out of list of lists?](https://stackoverflow.com/questions/952914/how-to-make-a-flat-list-out-of-list-of-lists) — wjandrea, Aug 22 '20 at 18:17
@wjandrea - not really, they have just lists but in my question i have lists and tuple. It is similiar question, thank you — ajayramesh, Aug 22 '20 at 18:29
@ajayramesh It's the same process, but yeah yours requires another nesting. This is also similar, but more complex: [Flatten an irregular list of lists](https://stackoverflow.com/q/2158395/4518341) — wjandrea, Aug 22 '20 at 18:40

han solo · Accepted Answer · 2020-08-22T18:29:19.773

2

You can just use itertools.chain.from_iterable over itertools.chain of those like,

>>> list(itertools.chain.from_iterable(itertools.chain(l1, l2, l3)))

Note: If all you need to do is iterate over the values, i'd drop the list creation, otherwise it is fine.

Although, i see you are working with numpy. Then you can just flatten the array like,

>>> import numpy as np
>>> 
>>> l1=[(260.3, 185.0), (268.01, 499.16)]
>>> l2=[(268.01, 500.87), (678.9, 506.0)]
>>> l3=((149.86, 354.48), (182.39, 344.2))
>>> 
>>> data = np.array([l1, l2, l3])
>>> data
array([[[260.3 , 185.  ],
        [268.01, 499.16]],

       [[268.01, 500.87],
        [678.9 , 506.  ]],

       [[149.86, 354.48],
        [182.39, 344.2 ]]])

>>> data.flatten()
array([260.3 , 185.  , 268.01, 499.16, 268.01, 500.87, 678.9 , 506.  ,
       149.86, 354.48, 182.39, 344.2 ])
>>> list(_)
[260.3, 185.0, 268.01, 499.16, 268.01, 500.87, 678.9, 506.0, 149.86, 354.48, 182.39, 344.2]

edited Aug 22 '20 at 18:29

answered Aug 22 '20 at 18:10

han solo

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19

Sorry about that. Updated :) – han solo Aug 22 '20 at 18:12
Glad i could be of help : ) – han solo Aug 22 '20 at 18:21
1

@ajayramesh Please check the update. When working with `numpy`, you rarely wanna use `list`, `numpy` usually have best things – han solo Aug 22 '20 at 18:30
makes sense, since my goal is to get 1-D numpy array. Thank you again again:) – ajayramesh Aug 22 '20 at 18:32
Yeah, no problem : ) – han solo Aug 22 '20 at 18:34

score 0 · Answer 2 · answered Aug 22 '20 at 18:11

If your goal ist to simply flatten the lists of tupels, you can use this:

[item for sublist in zip(l1,l2,l3) for tupel in sublist for item in tupel]

Out[4]: 
[260.3,
 185.0,
 268.01,
 500.87,
 149.86,
 354.48,
 268.01,
 499.16,
 678.9,
 506.0,
 182.39,
 344.2]

score 0 · Answer 3 · answered Aug 22 '20 at 18:12

Use this recursive function.

def unpack(item):
    result = []
    if item is not None:
        if type(item) in [list, tuple]:
            for element in item:
                result.extend(unpack(element))
        elif type(item) is float:
            for elemtn in item:
                result.append(item)
    return result 
l1=[(260.3, 185.0), (268.01, 499.16)]
l2=[(268.01, 500.87), (678.9, 506.0)]
l3=((149.86, 354.48), (182.39, 344.2))
result = unpack(l1)+unpack(l2)+unpack(l3)

Unpack series of tuples and lists into 1-d list?

Error

Expected output

3 Answers3