numpy: summing every element of numpy array with every element of another

问题

I'm coming to python from Matlab. In Matlab, given two vectors that are not necessarily the same length, they can be added if one is a row vector and one is a column vector.

v1 = [1 3 5 7]

v2 = [2 4 6]'

v1 + v2

ans =

 3     5     7     9
 5     7     9    11
 7     9    11    13

I am trying to produce the same behavior in python given two numpy arrays. Looping first came to mind:

import numpy as np
v1 = np.array([1,3,5,7])
v2 = np.array([2,4,6])
v3 = np.empty((3,4,))
v3[:] = np.nan

for i in range(0,3):
    v3[i,:] = v1 + v2[i]

Is there a more concise and efficient way?

回答1:

import numpy as np

v1 = np.array([1, 3, 5, 7])
v2 = np.array([2, 4, 6])

v1 + v2[:, None]

You can read more about numpy's broadcasting rules.

回答2:

Try this out:

for i in v2:
  z = []
  for j in v1:
    z.append(i+j)
  
  print(z)

来源：https://stackoverflow.com/questions/63286737/numpy-summing-every-element-of-numpy-array-with-every-element-of-another