convert numpy array of lists to array of int

Question

I have a 2D numpy array of single element lists:

aaa = np.array(
[[ [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0] ],
 [ [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0] ],
 [ [0], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4] ] ]
)

How can I turn the inner list into an int so I would have:

nnnn = np.array(
    [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
     [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
     [0, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 ]]
)

It sounds simple but anything I have tried I still end up with a list.

I tried sum() as a technique for summing the values in a list, but only ended up summing the whole lot.

I think the simplest solution is in the second dupe https://stackoverflow.com/questions/37152031/numpy-remove-a-dimension-from-np-array - `aaa[:,:,0]` — Tomerikoo, Jul 07 '22 at 08:38

Kins · Answer 1 · 2022-07-08T08:55:22.593

-1

You can do:

nnnn = np.array([l.flatten() for l in aaa])

You can also use reshape:

nnnn = aaa.reshape(-1, aaa.shape[1])

Or even simpler:

nnnn = aaa[:,:,0]

It is useful to note that the last solution returns a view, not a copy. Meaning that changes you apply to the new array will also be reflected in the old array

edited Jul 08 '22 at 08:55

answered Jul 07 '22 at 08:28

Kins

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Or just `aaa.reshape(arr.shape[:-1])` – Tomerikoo Jul 07 '22 at 08:33
1

Or even simpler `aaa[:,:,0]` – Tomerikoo Jul 07 '22 at 08:36
1

Thanks for the ideas everybody. I dont understand how this is interpreted as a change in dimensions though. I start with a 2D array and want to end with a 2D array. Regardless aaa[:,0] does what I want and gives an array of numbers – jc508 Jul 07 '22 at 23:56
You actually start with a 3D array: `aaa.shape` returns `(3,20,1)` – Kins Jul 08 '22 at 07:51
You can also mark the answer as accepted for future users and better reference – Kins Jul 08 '22 at 08:52

convert numpy array of lists to array of int

1 Answers1