Comment by aborsy

19 hours ago

Yeah. Compare

A = [1, 2; 3, 4];

x = [5; 6];

y = A * x;

with this uglier version:

import numpy as np

A = np.array([[1, 2], [3, 4]])

x = np.array([[5], [6]])

y = A @ x

2 comments

aborsy

Reply
threeducks  18 hours ago

You don't have to wrap the lists in np.array if you use NumPy functions (or if one of the arguments already is a NumPy array, which usually is the case):

    from numpy import *

    A = [[1, 2], [3, 4]]
    x = [[5], [6]]
    y = dot(A, x)

  • nis251413  1 hour ago

    That's nice, but only works, as I understand it, if you use numpy-only functions, which means that you should not use those who denote also base-pythonic, eg +,* etc operations, because then they are interpreted differently. Eg `A + x` gives

        [[1, 2], [3, 4], [5], [6]]

    instead of

        array([[ 6,  7],[ 9, 10]])

    You have to keep track of the context there to know what you can do and what not I guess, which is not ideal.