Turn list of arrays into an array of lists

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Turn list of arrays into an array of lists - Cola_Reb - Jul-19-2022

Hey everyone,

I am currently struggling with the structure of data I receive. As a result of another (not important here) function I get a list filled with numpy arrays at a large scale (about 20 thousand entries):

first_array=[array([[1, 0, 2, 4, 3]], dtype=int64),
 array([[2, 6, 8, 3, 3]], dtype=int64),
 array([[0, 0, 4, 3, 3]], dtype=int64),
 array([[4, 4, 3, 2, 3]], dtype=int64),
...]

For the further procession of this data I need this input in the reverse structure: An array of lists like the following form:

output_array=array([
       [1, 0, 2, 4, 3],
       [2, 6, 8, 3, 3],
       [0, 0, 4, 3, 3],
       [4, 4, 3, 2, 3],
....])

Is there a way of doing this in a way that keeps the computational time low? Huh

RE: Turn list of arrays into an array of lists - paul18fr - Jul-19-2022

If you change "array" to "np.array" and int64 to "int", then at least the code works:

import numpy as np

Input=[np.array([[1, 0, 2, 4, 3]], dtype=int),
       np.array([[2, 6, 8, 3, 3]], dtype=int),
       np.array([[0, 0, 4, 3, 3]], dtype=int),
       np.array([[4, 4, 3, 2, 3]], dtype=int)]

Input2Array = np.asarray(Input).reshape(4, 5)

print(Input2Array)

Output:[[1 0 2 4 3]
 [2 6 8 3 3]
 [0 0 4 3 3]
 [4 4 3 2 3]]

RE: Turn list of arrays into an array of lists - jefsummers - Jul-20-2022

Just a comment - input is a terrible name for a variable, as it overrides the standard function. You can't use input() after that...

RE: Turn list of arrays into an array of lists - Cola_Reb - Jul-20-2022

(Jul-19-2022, 05:21 PM)paul18fr Wrote: If you change "array" to "np.array" and int64 to "int", then at least the code works:

import numpy as np

first_array=[np.array([[1, 0, 2, 4, 3]], dtype=int),
       np.array([[2, 6, 8, 3, 3]], dtype=int),
       np.array([[0, 0, 4, 3, 3]], dtype=int),
       np.array([[4, 4, 3, 2, 3]], dtype=int)]

Input2Array = np.asarray(Input).reshape(4, 5)

print(Input2Array)

Output:[[1 0 2 4 3]
 [2 6 8 3 3]
 [0 0 4 3 3]
 [4 4 3 2 3]]

Is there also a possibility if it is not possible to change the numpy array to int-type?

RE: Turn list of arrays into an array of lists - Larz60+ - Jul-20-2022

Please pay attention to post by jeffsummers. It is important, taboo actually to use reserved words in your code.
input is used by python, and you are redefining it.

RE: Turn list of arrays into an array of lists - paul18fr - Jul-20-2022

I fully agree with jefsummers and Larz60+, and that's why I've changed in first letter in upper case ... but it may lead to a misunderstanding in a future!

@Cola_Reb: it might be interesting to show how did you make your list

RE: Turn list of arrays into an array of lists - Cola_Reb - Jul-20-2022

It is quite complicated to reproduce this in a simplified way but I will give it a try. I hope it will be clear.

First of all I have an array of the form:

first_array=np.array([0, 0, 0, 0, 0, 1, 2, 2, 2, 3, 3, 4], dtype=int64)

Then I have a function_a that takes this array and calculates a value for each entry which is summed up in a 1-dimensional array with the length of 5. It is hard to find an easy example for this calculation without posting a ton of code, so this is replaced here by a simple random_function, that returns an array of dtype=64 (not modifiable unfortunately):

def function_a(first_array):
    
    total_results = [0 for i in range(5)]

    for row_index in range(first_array.shape[0]):

        total_results += random_function([row_index])
    
    return total_results



def random_function(entry_array):
        
    result_for_entry = np.random.choice([0, 1], size=5, p=[.1, .9])
    result_for_entry = result_for_entry.astype(np.int64)
    
    return result_for_entry


function_a(first_array)

Output:
array([ 9, 11, 10, 12, 11], dtype=int64)

But I have to to this for a larger data set of this example form (here only 5 arrays are assumed, in fact there are 15.000):

testdata=np.array([array([0, 0, 0, 0, 0, 1, 2, 3, 3, 3, 4, 4], dtype=int64),
       array([0, 1, 2, 2, 2, 3, 3, 4, 4], dtype=int64),
       array([0, 0, 1, 3, 4], dtype=int64), array([0, 0], dtype=int64),
       array([0, 1, 2, 2, 4, 4], dtype=int64)], dtype=object)

For this purpose I wrote function_b which results in the mentioned result structure of a list of arrays:

def function_b(testdata):

    results = [[0 for i in range(5)] for k in range(5)]
    
    for i in range(5):
        results[i] = function_a(testdata[i])
       
        
    return results

function_b(testdata)

Output:[array([12, 10, 11, 12, 11], dtype=int64),
 array([8, 7, 9, 8, 7], dtype=int64),
 array([5, 5, 5, 5, 5], dtype=int64),
 array([2, 2, 2, 2, 2], dtype=int64),
 array([6, 6, 6, 6, 5], dtype=int64)]

I hope I explained the structure in an understandable way. Help is much appreciated how I can get the final results as an array of lists.

Thank you!