Convert a list of numpy vectors to 2D numpy array

Question

I have a list of numpy arrays. My list contains 5000 numpy arrays and each one has the size (1x1000). I want to construct a numpy array of size 5000x1000. I am trying to do something like:

db_array = np.asarray(db_list) # my db_list has 5000 samples of 1x1000 size

The result was a matrix of size (5000, 1, 1000). How can I construct a matrix with size (5000, 1000)?

I tried reshape and the reuslt was the same. db_array = db_array.reshape(5000, 1000). I got (5000, 1, 1000) when I tried db_array.shape — konstantin
– konstantin, Commented Mar 21, 2018 at 10:34

timgeb · Accepted Answer · 2018-03-21 10:30:43Z

2

An MCVE would help here, but if I understand correctly, just use the numpy.array constructor.

>>> import numpy as np
>>> arraylist = [np.array([1,2,3]), np.array([1,2,3])]
>>> arraylist
[array([1, 2, 3]), array([1, 2, 3])]
>>> np.array(arraylist)
array([[1, 2, 3],
       [1, 2, 3]])

answered Mar 21, 2018 at 10:30

timgeb

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2 Comments

konstantin Over a year ago

As a matter of fact in order to work I convert the list using the the np.array() but then i needed also to reshape. With np.asarray() it did not work.

timgeb Over a year ago

@konstantin then your list does have a different format than the one in my demo which you did not tell us about.

Anurag Reddy · Accepted Answer · 2018-03-21 20:19:08Z

2

So, just initialize the list as a simple numpy array

import numpy as np

list = [np.array([1,2,3]), np.array([1,2,3])]
new_array = np.array(list)
print (new_array)
print (new_array.shape)

answered Mar 21, 2018 at 20:19

Anurag Reddy

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