How to undo an array inside of a list in Python?

Question

I know there are several topics about flattening lists and arrays. But I could not find an answer to my question in specific. I am trying to get all possible combinations of a matrix with a vector as follows:

import numpy as np
from itertools import product

Var1 = np.array([1,2,3])
Var2 = np.array([10,20,30])
Var3 = np.array([100,200,300])
Var4 = np.array([500,1000,1500])

First3Var = [Var1,Var2,Var3]

Combinations = list(product(First3Var, Var4))

This works fine, "Combinations" is almost what I want. However, I now get an array inside a list. I want it to be an array with 4 columns, not with 2. Does anyone know how I undo this nested array? I hope my question is clear. Thanks!

Answer 1

You can do [np.append(i,j) for (i,j) in Combinations] and use it as a list or as an np.array() .

import numpy as np
from itertools import product

Var1 = np.array([1,2,3])
Var2 = np.array([10,20,30])
Var3 = np.array([100,200,300])
Var4 = np.array([500,1000,1500])

First3Var = [Var1,Var2,Var3]

Combinations = product(First3Var, Var4)
Combinations = np.array([np.append(i,j) for (i,j) in Combinations])

Now Combinations is a 4-column matrix.

[[   1    2    3  500]
 [   1    2    3 1000]
 [   1    2    3 1500]
 [  10   20   30  500]
 [  10   20   30 1000]
 [  10   20   30 1500]
 [ 100  200  300  500]
 [ 100  200  300 1000]
 [ 100  200  300 1500]]