Adding numpy arrays to numpy array in a for loop

Question

I have tried to add numpy arrays (multiple of numpy_array) in a for loop to a list where each numpy array might have varies shapes like (but let us say each has (10, 64)). So each array has 64 columns and might have as many rows as possible. What I did was the following:

l_arr = numpy_array[indices, :]
list_arr.append(l_arr.tolist())

Then,

numpy_from_list= np.array(list_arr)

But this seems to add extra dimension. For example If I added 3 numpy arrays each of size (10, 64) to a list and then convert a list to a numpy. I would get (3, 10, 64), but instead I want (30, 64).

for i in range(3):
    l_arr = numpy_array[indices, :]
    list_arr.append(l_arr.tolist())
    numpy_from_list= np.array(list_arr)

Can you please help me with that?

try to use numpy's np.stack() function

sehan2
– sehan2

2021-07-31 15:01:19 +00:00
Commented Jul 31, 2021 at 15:01 — sehan2
– sehan2, Commented Jul 31, 2021 at 15:01
@sehan2. Thank you, but I got same result.

Avv
– Avv

2021-07-31 15:04:10 +00:00
Commented Jul 31, 2021 at 15:04 — Avv
– Avv, Commented Jul 31, 2021 at 15:04

sehan2 · Accepted Answer · 2021-07-31 15:07:44Z

1

Here you go:

arrays = [np.random.randint(0,10,(10, 64)) for i in range(3)]
res = np.vstack(arrays)

answered Jul 31, 2021 at 15:07

sehan2

1,8551 gold badge14 silver badges27 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Avv Over a year ago

While running the loop, how I can set a condition that size of stacked arrays should not exceed 30 for example? I did your code and it works, but it has issues as the list size of 3 has actual array sizes of 30 by 64. So I can not set a condition to stop the loop based on list size like while len(list_numpy_arryas) <=30:

Avv Over a year ago

I am adding arrays iteratively not in a single call as you did with arrays above.

sehan2 Over a year ago

your arrays have to have compatible dimensions to stack them

Avv Over a year ago

They are not compatible unfortunatley. One might have (10, 64) while another might have (3, 64), etc. So I first added them to a list and once I finish I stacked them as you did, but the issue is I want to stop once I added a total of (64, 64) from all arrays. Can you help me with that please?

sehan2 Over a year ago

look into 'list comprehensions' or use a for loop as you did above

|

Collectives™ on Stack Overflow

Adding numpy arrays to numpy array in a for loop

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related