NumPy | Multiply 2D Array to 1D Array

Last Updated : 11 Jul, 2025

Given two NumPy arrays, the task is to multiply a 2D array with a 1D array, each row corresponding to one element in NumPy.

You can follow these methods to multiply a 1D array into a 2D array in NumPy:

Using np.newaxis()
Using axis as none
Using transpose()

Let's understand them better with Python program examples:

Using np.newaxis()

The np.newaxis() method of the NumPy library allows us to increase the dimension of an array by 1 dimension. We use this method to perform element-wise multiplication by reshaping the 1D array to have a second-dimension

Example:

Python3

import numpy as np

ini_array1 = np.array([[1, 2, 3], [2, 4, 5], [1, 2, 3]])
ini_array2 = np.array([0, 2, 3])

# printing initial arrays
print(&quot;initial array&quot;, str(ini_array1))

# Multiplying arrays
result = ini_array1 * ini_array2[:, np.newaxis]

# printing result
print(&quot;New resulting array: &quot;, result)

Output

initial array [[1 2 3]
 [2 4 5]
 [1 2 3]]
New resulting array:  [[ 0  0  0]
 [ 4  8 10]
 [ 3  6  9]]

Using axis as none

We use None, to add a new axis to the 1D NumPy array. This reshapes the 1D array to a 2D array and allows us to multiply it with a 2D array.

Example:

Python3

# Python code to demonstrate
# multiplication of 2d array
# with 1d array

import numpy as np

ini_array1 = np.array([[1, 2, 3], [2, 4, 5], [1, 2, 3]])
ini_array2 = np.array([0, 2, 3])

# printing initial arrays
print(&quot;initial array&quot;, str(ini_array1))

# Multiplying arrays
result = ini_array1 * ini_array2[:, None]

# printing result
print(&quot;New resulting array: &quot;, result)

Output

initial array [[1 2 3]
 [2 4 5]
 [1 2 3]]
New resulting array:  [[ 0  0  0]
 [ 4  8 10]
 [ 3  6  9]]

Using transpose

Using NumPy T attribute, we transpose the 2D array to multiply it with a 1D array and then transpose the resulting array to its original form.

Example:

Python3

# python code to demonstrate
# multiplication of 2d array
# with 1d array

import numpy as np

ini_array1 = np.array([[1, 2, 3], [2, 4, 5], [1, 2, 3]])
ini_array2 = np.array([0, 2, 3])

# printing initial arrays
print(&quot;initial array&quot;, str(ini_array1))

# Multiplying arrays
result = (ini_array1.T * ini_array2).T

# printing result
print(&quot;New resulting array: &quot;, result)

Output

initial array [[1 2 3]
 [2 4 5]
 [1 2 3]]
New resulting array:  [[ 0  0  0]
 [ 4  8 10]
 [ 3  6  9]]

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NumPy | Multiply 2D Array to 1D Array

Using np.newaxis()

Using axis as none

Using transpose

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NumPy | Multiply 2D Array to 1D Array

Using np.newaxis()

Using axis as none

Using transpose

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