Matrix-Vector Multiplication

def matvec(M, v):
    result = []
    for i in range(len(M)):
        s = 0
        for j in range(len(M[i])):
            s += M[i][j] * v[i]
        result.append(s)
    return result

print(matvec([[1, 2], [3, 4]], [5, 6]))  # expected [17, 39]