NumPy: Build an array of all combinations of three NumPy arrays

Last update on March 24 2025 13:39:09 (UTC/GMT +8 hours)

Build Array of All Combinations of Three Arrays

Write a NumPy program to build an array of all combinations of three NumPy arrays.

Sample Solution:

Python Code:

# Importing the NumPy library and aliasing it as 'np'
import numpy as np

# Creating three lists: 'x', 'y', and 'z'
x = [1, 2, 3]
y = [4, 5]
z = [6, 7]

# Printing the original arrays
print("Original arrays:")
print("Array-1")
print(x)
print("Array-2")
print(y)
print("Array-3")
print(z)

# Creating a new NumPy array by meshgrid to combine elements from 'x', 'y', and 'z'
new_array = np.array(np.meshgrid(x, y, z)).T.reshape(-1, 3)

# Printing the combined array obtained from meshgrid
print("Combine array:")
print(new_array)

Sample Output:

Original arrays:
Array-1
[1, 2, 3]
Array-2
[4, 5]
Array-3
[6, 7]
Combine array:
[[1 4 6]
 [1 5 6]
 [2 4 6]
 [2 5 6]
 [3 4 6]
 [3 5 6]
 [1 4 7]
 [1 5 7]
 [2 4 7]
 [2 5 7]
 [3 4 7]
 [3 5 7]]

Explanation:

In the above code –

• x = [1, 2, 3]: Define the first list 'x' with elements 1, 2, and 3.
• y = [4, 5]: Define the second list 'y' with elements 4 and 5.
• z = [6, 7]: Define the third list 'z' with elements 6 and 7.
• np.meshgrid(x, y, z): Create a meshgrid from the input lists 'x', 'y', and 'z'. The meshgrid is a multidimensional grid that contains the coordinates of all possible combinations of elements from the input lists.
• np.array(np.meshgrid(x, y, z)).T: Transpose the meshgrid to rearrange the axes.
• .reshape(-1, 3): Reshape the transposed array into a 2D array with 3 columns and an automatically calculated number of rows.
• new_array = ...: Assign the reshaped array to the variable 'new_array'.
• Finally print() function prints the resulting 'new_array' containing all possible combinations of elements from lists 'x', 'y', and 'z'.

For more Practice: Solve these Related Problems:

• Write a NumPy program to generate the full combination of elements from three 1D arrays using np.meshgrid.
• Create a function that returns an array where each row is a unique triplet from the input arrays.
• Test the combination generator with arrays of varying lengths and verify the total number of combinations.
• Implement an alternative solution using itertools.product and converting the result into a NumPy array.

Python-Numpy Code Editor: