Numpy numpy.dot Function

  1. Syntax of numpy.dot():
  2. Example Codes: numpy.dot() Method to Find Dot Product

Python Numpynumpy.dot() function calculates the dot product of two input arrays.

Syntax of numpy.dot():

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

Parameters

a Array-like. 1st array or scalar whose dot product is be calculated
b Array-like. 2nd array or scalar whose dot product is be calculated
out Array. An optional argument whose data-type must be the same as the expected data-type of output

Return

It returns the dot product of input vectors. If both inputs are scalars, it produces a 1-D array otherwise n-dimensional array.

Raise ValueError if the last dimension of the 1st input array is not equal to the second-to-last dimension of the 2nd input array.

Example Codes: numpy.dot() Method to Find Dot Product

When Both Inputs Are 1-D Arrays

import numpy as np

a=4
b=5

prod=np.dot(a,b)
print(prod)

Output:

20

Here, since both a and b are 1-D arrays, the np.dot() function simply returns a scalar, which is a simple product of both the numbers.

When Both Inputs Are Vectors

import numpy as np

a=np.array([3,4])
b=np.array([4,5])

prod=np.dot(a,b)
print(prod)

Output:

32

It calculates the dot product of vectors.

The dot product of two vectors [x1,y1] and [x2,y2] is given by x1*x2+y1*y2.

When Both Inputs Are 2-Dimensional Arrays

import numpy as np

a=np.array([[3,4],
          [2,3]])
b=np.array([[4,5],
          [2,3]])

prod=np.dot(a,b)
print(prod)

Output:

[[20 27]
 [14 19]]

It calculates the product of matrices.