Multiply matrix by list in Python

Question

I am looking for a way to achieve the following in Python and can’t figure out how to do it:

a=[[0,1],[1,0],[1,1]]
b=[1,0,5]

c=hocuspocus(a,b)

--> c=[[0,1],[0,0],[5,5]]

So basically I would like to multiply the different matrix rows in a with the list b.

Thanks a lot in advance!

Asked By: Bart

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Source

Answer 1

hocuspocus = lambda a,b: [[r*q for r in p] for p, q in zip(a,b)]

Answered By: Lie Ryan

Answer 2

Use Numpy, it has a function for cross multiplying, and other useful tools for matricies.

import * from numpy as np

a=[[0,1],[1,0],[1,1]]
b=[1,0,5]

prod = a * b

Answered By: Rob Wagner

Answer 3

Python lists don’t support that behaviour directly, but Numpy arrays do matrix multiplication (and various other matrix operations that you might want) directly:

>>> a
array([[0, 1, 1],
       [1, 0, 1]])
>>> b
array([1, 0, 5])
>>> a * b
array([[0, 0, 5],
       [1, 0, 5]])

Answered By: lvc

Multiply matrix by list in Python

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