Reshape each array in a list of arrays python

Question

I have an list of arrays, I want to reshape each array in the list and then stack.

A sample below

C = np.array([[-127, -108, -290],
       [-123,  -83, -333],
       [-126,  -69, -354],
       [-146, -211, -241],
       [-151, -209, -253],
       [-157, -200, -254]])



D = np.array([[-129, -146, -231],
       [-127, -148, -238],
       [-132, -157, -231],
       [ -93, -355, -112],
       [ -95, -325, -137],
       [ -99, -282, -163]])



E = np.array(([[-141, -133, -200],
       [-132, -123, -202],
       [-119, -117, -204],
       [-107, -210, -228],
       [-101, -194, -243],
       [-105, -175, -244]]))


ArrayList = (C,D,E)

to reshape an individual array I do the following

newArray = ArrayList[0].reshape(1,-1)

and produces the desired result

array([[-127, -108, -290, -123,  -83, -333, -126,  -69, -354, -146, -211,
        -241, -151, -209, -253, -157, -200, -254]])

I tried writing a for loop to go through each item

newArray = []
for i in ArrayList:
    i.reshape(1,-1)
    newArray.append(i)

But I got the same product as what I started with. The desired output is shown below

(array([[-127, -108, -290, -123,  -83, -333, -126,  -69, -354, -146, -211,
         -241, -151, -209, -253, -157, -200, -254]]),
 array([[-129, -146, -231, -127, -148, -238, -132, -157, -231,  -93, -355,
         -112,  -95, -325, -137,  -99, -282, -163]]),
 array([[-141, -133, -200, -132, -123, -202, -119, -117, -204, -107, -210,
         -228, -101, -194, -243, -105, -175, -244]]))

Any help appreciated.

Is your desired result multidimensional or flattened? The double [ are a red flag. You also might check out numpy hstack and vstack — luthervespers
– luthervespers, Commented Mar 27, 2022 at 2:19

constantstranger · Accepted Answer · 2022-03-27 02:16:54Z

2

I think you just need to do this:

newArray = []
for i in ArrayList:
    j = i.reshape(1,-1)
    newArray.append(j)

print(newArray)

Output:

[array([[-127, -108, -290, -123,  -83, -333, -126,  -69, -354, -146, -211,
        -241, -151, -209, -253, -157, -200, -254]]), 
array([[-129, -146, -231, -127, -148, -238, -132, -157, -231,  -93, -355,
        -112,  -95, -325, -137,  -99, -282, -163]]), 
array([[-141, -133, -200, -132, -123, -202, -119, -117, -204, -107, -210,
        -228, -101, -194, -243, -105, -175, -244]])]

answered Mar 27, 2022 at 2:16

constantstranger

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mozway · Accepted Answer · 2022-03-27 02:33:36Z

1

What about using a list comprehension?

newArray = [i.reshape(1,-1) for i in ArrayList]

Output:

[array([[-127, -108, -290, -123,  -83, -333, -126,  -69, -354, -146, -211,
         -241, -151, -209, -253, -157, -200, -254]]),
 array([[-129, -146, -231, -127, -148, -238, -132, -157, -231,  -93, -355,
         -112,  -95, -325, -137,  -99, -282, -163]]),
 array([[-141, -133, -200, -132, -123, -202, -119, -117, -204, -107, -210,
         -228, -101, -194, -243, -105, -175, -244]])]

answered Mar 27, 2022 at 2:33

mozway

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1 Comment

Spooked Over a year ago

thats a nice one liner

Mushroomator · Accepted Answer · 2022-03-27 02:16:42Z

0

reshape() does not guarantee that it will return a "view", as it is called in the docs, to the same array. See the docs for this. It could be a copy of the original array, hence you need to use the return value and append the return value to your array. This should fix your problem.

import numpy as np

C = np.array([[-127, -108, -290],
       [-123,  -83, -333],
       [-126,  -69, -354],
       [-146, -211, -241],
       [-151, -209, -253],
       [-157, -200, -254]])



D = np.array([[-129, -146, -231],
       [-127, -148, -238],
       [-132, -157, -231],
       [ -93, -355, -112],
       [ -95, -325, -137],
       [ -99, -282, -163]])



E = np.array(([[-141, -133, -200],
       [-132, -123, -202],
       [-119, -117, -204],
       [-107, -210, -228],
       [-101, -194, -243],
       [-105, -175, -244]]))


ArrayList = (C,D,E)

newArray = []
for i in ArrayList:
    newArray.append(i.reshape(1,-1))

print(newArray)

Expected output

[array([[-127, -108, -290, -123,  -83, -333, -126,  -69, -354, -146, -211,
        -241, -151, -209, -253, -157, -200, -254]]), array([[-129, -146, -231, -127, -148, -238, -132, -157, -231,  -93, -355,
        -112,  -95, -325, -137,  -99, -282, -163]]), array([[-141, -133, -200, -132, -123, -202, -119, -117, -204, -107, -210,
        -228, -101, -194, -243, -105, -175, -244]])]

answered Mar 27, 2022 at 2:16

Mushroomator

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1 Comment

hpaulj Over a year ago

i.reshape(1,-1) doesn't work in-place, copy or view.

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