Error then trying to multiply two arrays by using '@'

Question

I am trying to multiply two arrays by using '@' but this is the error I get

a@b

unsupported operand type(s) for @: 'list' and 'list'

I read that '@' is used for matrix multiplication, which is what I need

Answer 1

From the error message it appears as though you are using lists. You need to use arrays for which you can use the numpy module like this:

import numpy as np

x = [1,2,3,4]
y = [10,20,30,40]

x = np.array(x)
y = np.array(y)

z = x@y
print(z)

which returns this:

300

If you want to multiply lists without numpy you can do this:

# method 1
z = 0
for i, v in enumerate(x):
    z = z + (x[i]*y[i])
print(z)

# method 2
z = sum([x*y for x,y in zip(x,y)])
print(z)

Both would return the same value as above...