How to build an array of all combinations of two NumPy arrays?
Last Updated :
25 Apr, 2025
Our task is to build an array containing all possible combinations of elements from two NumPy arrays. To achieve this, we can utilize the np.meshgrid() function, which creates coordinate grids from the arrays. By reshaping these grids, we can generate a 2D array that holds every combination of values from the two input arrays.
Syntax:
numpy.meshgrid(*xi, copy=True, sparse=False, indexing='xy')
Examples of building an array of all combinations of two NumPy arrays
Example 1: Computing combinations of elements of Two NumPy arrays
This code demonstrates how to combine two 1D NumPy arrays using np.meshgrid() to create a 2D grid of coordinates and then reshape it into a 2D array.
Python
import numpy as np
a = np.array([1, 2])
b = np.array([4, 6])
print("Array-1")
print(a)
print("\nArray-2")
print(b)
res = np.array(np.meshgrid(a, b)).T.reshape(-1, 2)
print("\nCombine array:")
print(res)
OutputArray-1
[1 2]
Array-2
[4 6]
Combine array:
[[1 4]
[1 6]
[2 4]
[2 6]]
Explanation: Two 1D arrays a and b are created. np.meshgrid(a, b) creates coordinate grids from the arrays a and b. The result is reshaped into a 2D array with pairs of coordinates using .T.reshape(-1, 2). The combined array of all coordinate pairs is printed.
Example 2: Computing combinations of elements of Three NumPy arrays
This code demonstrates how to combine three 1D NumPy arrays using np.meshgrid() to create a 3D grid of coordinates and then reshape it into a 2D array of coordinate triples.
Python
import numpy as np
a = np.array([1, 2, 3])
b = np.array([4, 6, 4])
c = np.array([3, 6])
print("Array-1")
print(a)
print("Array-2")
print(b)
print("Array-3")
print(c)
res = np.array(
np.meshgrid(a, b, c)).T.reshape(-1, 3)
print("\nCombine array:")
print(res)
Output
Array-1
[1 2 3]
Array-2
[4 6 4]
Array-3
[3 6]
Combine array:
[[1 4 3]
[1 6 3]
[1 4 3]
[2 4 3]
[2 6 3]
[2 4 3]
[3 4 3]
[3 6 3]
[3 4 3]
[1 4 6]
[1 6 6]
[1 4 6]
[2 4 6]
[2 6 6]
[2 4 6]
[3 4 6]
[3 6 6]
[3 4 6]]
Explanation: The code begins by creating three 1D NumPy arrays, a, b, and c. Using np.meshgrid(a, b, c), coordinate grids are generated from these arrays. The result is then reshaped into a 2D array of coordinate triples by applying .T.reshape(-1, 3).
Example 3: Computing combinations of elements of Four NumPy arrays
This code demonstrates how to combine four 1D NumPy arrays into all possible combinations of their elements using np.meshgrid(). It creates a 4D coordinate grid and then reshapes the grid into a 2D array of coordinate quadruples.
Python
import numpy as np
a = np.array([50, 21])
b = np.array([4, 4])
c = np.array([1, 10])
d = np.array([7, 14])
print("Array-1")
print(a)
print("Array-2")
print(b)
print("Array-3")
print(c)
print("Array-4")
print(d)
res = np.array(np.meshgrid(a, b, c, d)).T.reshape(-1, 4)
print("\nCombine array:")
print(res)
Output
Array-1
[50 21]
Array-2
[4 4]
Array-3
[ 1 10]
Array-4
[ 7 14]
Combine array:
[[50 4 1 7]
[50 4 1 7]
[21 4 1 7]
[21 4 1 7]
[50 4 10 7]
[50 4 10 7]
[21 4 10 7]
[21 4 10 7]
[50 4 1 14]
[50 4 1 14]
[21 4 1 14]
[21 4 1 14]
[50 4 10 14]
[50 4 10 14]
[21 4 10 14]
[21 4 10 14]]
Explanation: The code creates four 1D arrays (a, b, c, d) and uses np.meshgrid() to generate a 4D coordinate grid. It then reshapes the grid into a 2D array of coordinate quadruples using .T.reshape(-1, 4). The result is a 2D array containing all possible combinations of values from the four arrays.
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