我必须编写一个有两个参数的函数（两个数字列表，并返回其内积），而不使用列表理解，有什么想法吗？

Question

def inner_product(vec1,vec2):
    if len(vec1)==len(vec2) and len(vec1)!=0:
        return sum([vec1[n]*vec2[n] for n in range(len(vec1))])
    else:
        return 0

Is the code that I built contain using list comprehension? if yes what can I do instead of this?

Answer 1

Yes.
Without list comprehension, it would be something like below.

def inner_product(vec1,vec2):
    if len(vec1)==len(vec2) and len(vec1)!=0:
        temp=[]
        for n in range(len(vec1)):
            temp.append(vec1[n]*vec2[n])
        return sum(temp)
    else:
        return 0

Answer 2

A basic for -loop approach.

def inner_product(vec1, vec2):
    result = 0
    if len(vec1) == len(vec2) and len(vec1) != 0:
        for i in range(len(vec1)):
            result += vec1[i] * vec2[i]
    return result


print(inner_product([1, 2, 3], [4, 5, 6]))
#32
print(inner_product([1, 2, 3], [4, 5, 6, 5555]))
#0

Notice that your current implementation returns 0 if the vectors have different length... but careful that a inner product return zero if and only if the two vectors are orthogonal to each other (assumed both vectors non zero)... and this geometrical result will fail. Raising an exception would be a good choice to fix it: raise Exception("Error, vectors non comparable")