CODEWITHSUNDEEP
pythonpython-3.xlistnesteddot-product
Lenka Marcanova
Lenka Marcanova

Reputation: 11

dot product within a nested list python

I would like to ask whether it is possible to create a dot product within this nested list a = [[1,2,3],[2,4,2],[1,2,3], [5,6,7]] in Python without using numpy

I tried:

a = [[1,2,3],[2,4,2],[1,2,3], [5,6,7]]

for x, y in zip(a):
    temp = []
    for m, n in zip(x):
        temp.append(m * n)
    c.append([sum(temp)])

print(c)

However I got an error message:

not enough values to unpack (expected 2, got 1)

Upvotes: 0

Views: 338

Answers (1)

Brad Solomon
Brad Solomon

Reputation: 40908

You can unpack and zip a, then use operator and reduce (built-in in Python 2.x):

>>> from functools import reduce
>>> from operator import mul
>>> sum(reduce(mul, i) for i in zip(*a))
232

In other words:

>>> i, j, k = zip(*a)

>>> i
(1, 2, 1, 5)
>>> j
(2, 4, 2, 6)
>>> k
(3, 2, 3, 7)

Then you take sum( (1*2*1*5, 2*4*2*6, 3*2*3*7) ).

Upvotes: 1

Related Questions