np.dot function - Python NumPy dot() Function

NumPy dot() Function:

np.dot function: The dot() method in the NumPy module is used to do the dot product of two arrays. Specifically,

It is the inner product of vectors if both a and b are 1-D arrays (without complex conjugation).
Matrix multiplication is used when both a and b are 2-D arrays, however, matmul or a @ b is preferred.
If either a or b is 0-D (scalar), it is equivalent to multiply and using numpy.multiply(a, b) or a * b is preferred.
It is a sum product over the last axis of a and b if “a” is an N-D array and “b” is a 1-D array.
It is a sum product over the final axis of a and the second-to-last axis of b if “a” is an N-D array and “b” is an M-D array (where M>=2).

dot(a, b)[i, j, k, m] = sum(a[i, j, :] * b[k, : ,m])

Syntax:

numpy.dot(a, b, out=None)

Parameters

a: This is required. It is the first array_like parameter given as input.

b: This is required. It is the second array_like parameter given as input.

out: This is optional. It is the location where the result will be stored.

Return Value:

.dot() python: The dot product of a and b is returned. A scalar is returned if a and b are both scalars or both 1-D arrays; otherwise, an array is returned. If out is specified, it will be returned.

Note: If the last dimension of a is not the same size as the second-to-last dimension of b, the ValueError exception is thrown.

NumPy dot() Function in Python

Example1

Approach:

Import numpy module using the import keyword.
Pass two random numbers as the arguments to the dot() function of numpy module to calculate the dot product of the given two numbers.
Store it in a variable.
Print the dot product of the given two numbers.
The Exit of the Program.

Below is the implementation:

# Import numpy module using the import keyword
import numpy as np
# Pass two random numbers as the arguments to the dot() function
# of numpy module to calculate the dot product of given two numbers
# Store it in a variable.
rslt = np.dot(4, 6)
# Print the dot product of the given two numbers 
print("The dot product of given two numbers = ", rslt)

Output:

The dot product of given two numbers = 24

Example2

Approach:

Import numpy module using the import keyword.
Give the first array as static input and store it in a variable.
Give the second array as static input and store it in another variable.
Pass the given two array’s as an argument to the dot() function of numpy module to get the inner dot product of the given two arrays.
Store it in another variable.
Print the inner dot product of the given two arrays.
The Exit of the Program.

Below is the implementation:

# Import numpy module using the import keyword
import numpy as np
# Give the first array as static input and store it in a variable.
fst_arry = [4, 9, 2]
# Give the second array as static input and store it in another variable.
scnd_arry = [6, 3, 5]
# Pass the given two array's as an argument to the dot() function of numpy module 
# to get the inner dot product of the given two arrays.
# Store it in another variable.
rslt = np.dot(fst_arry, scnd_arry)
# Print the inner dot product of the given two arrays.
print("The inner dot product of the given two arrays = ", rslt)

Output:

The inner dot product of the given two arrays = 61

Example3

Numpy dot function: Here dot() function is used to calculate the dot product for the complex numbers

# Import numpy module using the import keyword
import numpy as np
# Pass the random list of complex numbers as an argument to the array() function 
# to create an array. 
# Store it in a variable.
fst_arry = np.array([2+4j, 1+3j])
# Pass the random list of complex numbers as an argument to the array() function 
# to create another array. 
# Store it in another variable.
scnd_arry = np.array([1+2j, 3+2j])
# Pass the given two array's as the argument to the dot() function of numpy module 
# to get the dot product of the given two arrays of complex numbers.
# Store it in another variable.
rslt = np.dot(fst_arry, scnd_arry)
# Print the dot product of the given two arrays of complex numbers.
print("The dot product of the given two arrays of complex numbers = ")
print(rslt)

Output:

The dot product of the given two arrays of complex numbers = 
(-9+19j)

Example4

Dot function python: Here dot() function is used to calculate the dot product for the 2D arrays i.e matrix.

The dot() function returns matrix multiplication when two matrices are given.

# Import numpy module using the import keyword
import numpy as np
# Pass the random list(2D) as an argument to the array() function 
# to create an array. 
# Store it in a variable.
fst_arry = np.array([[5, 6], 
                     [1, 7]])
# Pass the random list(2D) as an argument to the array() function 
# to create another array. 
# Store it in another variable.
scnd_arry = np.array([[2, 4], 
                      [8, 7]])
# Pass the given two array's as the argument to the dot() function of numpy module 
# to get the dot product of the given two 2D arrays 
# Here it returns the matrix multiplcation of given arrays(matrices)
# Store it in another variable.
rslt = np.dot(fst_arry, scnd_arry)
# Print the matrix multiplcation of given two arrays(matrices)
print("The matrix multiplcation of given two arrays(matrices) = ")
print(rslt)

Output:

The matrix multiplcation of given two arrays(matrices) = 
[[58 62]
 [58 53]]

np.dot function – Python NumPy dot() Function

NumPy dot() Function in Python

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