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?

You can use

numpy.stack(arrays, axis=0)

if you have an array of arrays. You can specify the axis in case you want to stack columns and not rows.