def dot_product(vector_a, vector_b):
#base case
#error message if the vectors are not of the same length
if len(vector_a) != len(vector_b):
return "ERROR: both input vectors must be of the same length"
#multiply vector_a at position i with vector_b at position i
#sum the vector made
#return that vector
return sum([vector_a[i] * vector_b[i] for i in range(len(vector_a))])