Python: obtain multidimensional matrix as results from a function

Question

I have a multi-inputs function, say:

def bla(a, b):
    f = a + b
    return f

When I do something like

import numpy as np
bla(np.asarray([0.2,0.4]), np.asarray([2,4]))

The result is:

array([ 2.2,  4.4])

However, I want bla to be applied to each possible pair of my inputs( bla(0.2, 2) , bla(0.2, 4) , bla(0.4, 2) , bla(0.4, 4) ) and obtain the final result as a 2-D matrix. In this example, I want the result to be:

array([[2.2, 4.2],
[2.4, 4.4]
])

How can I do this? My original problem is that I have a function with three variables and one output, then I want to call the function by entering vectors for each variable so that I obtain a 3-D matrix as a result

Answer 1

Not sure if you want to do this without modifying bla() , but for your example at least that's where the change must be:

def bla(a, b):
    return np.asarray(a+n for n in b)

This operates on array a with each element of b , and builds an array with the results. Your example looks a little random (how did you get those .3 fractional parts?), but I'm guessing this is what you're trying to get at.

Answer 2

Provided your function bla can accept arrays instead of scalars, you could use meshgrid to prepare the inputs so that bla(A, B) returns the desired output:

import numpy as np
def bla(a, b):
    f = a + b
    return f

A, B = np.meshgrid([0.2,0.4], [2,4], sparse=True)
bla(A, B)

yields

array([[ 2.2,  2.4],
       [ 4.2,  4.4]])