David Folkner David Folkner - 4 months ago 41
Python Question

Numpy list of 1D Arrays to 2D Array

I have a large list files that contain 2D numpy arrays pickled through

numpy.save
. I am trying to read the first column of each file and create a new 2D array.

I currently read each column using
numpy.load
with a
mmap
. The 1D arrays are now in a list.

col_list = []
for f in file_list:
Temp = np.load(f,mmap_mode='r')
col_list.append(Temp[:,0])


How can I convert this into a 2D array?

Answer

You can just call np.array on the list of 1D arrays.

>>> import numpy as np
>>> arrs = [np.array([1,2,3]), np.array([4,5,6]), np.array([7,8,9])]
>>> arrs
[array([1, 2, 3]), array([4, 5, 6]), array([7, 8, 9])]
>>> arr2d = np.array(arrs)
>>> arr2d.shape
(3, 3)
>>> arr2d
array([[1, 2, 3],
       [4, 5, 6],
       [7, 8, 9]])
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