好吧，如果我必须诚实，我不知道你使用的一些路径在哪里，因为我找不到它们。我重新编写了你的代码，试图帮助你：

from lxml import html 
import requests
import json
asin = 'B0718Y23CQ'
page_response = requests.get('https://www.amazon.com/product-reviews/'+ asin)
parser = html.fromstring(page_response.content)
reviews_html = parser.xpath('//div[@class="a-section review"]')
reviews_arr = []
for review in reviews_html:
    review_dic = {}
    review_dic['title'] = review.xpath('.//a[@data-hook="review-title"]/text()')
    review_dic['rating'] = review.xpath('.//a[@class="a-link-normal"]/@title')
    review_dic['author'] = review.xpath('.//a[@data-hook="review-author"]/text()')
    review_dic['date'] = review.xpath('.//span[@data-hook="review-date"]/text()')
    review_dic['purchase'] = review.xpath('.//span[@data-hook="avp-badge"]/text()')
    review_dic['review_text'] = review.xpath('.//span[@data-hook="review-body"]/text()')
    review_dic['helpful_votes'] = review.xpath('.//span[@data-hook="helpful-vote-statement"]/text()')
    reviews_arr.append(review_dic)
print(json.dumps(reviews_arr, indent = 4))

输出方案为：

{
        "title": [
            "I find it very useful, I use for anything I need"
        ],
        "rating": [
            "5.0 out of 5 stars"
        ],
        "author": [
            "Nicoletta Delon"
        ],
        "date": [
            "on January 2, 2018"
        ],
        "purchase": [
            "Verified Purchase"
        ],
        "review_text": [
            "I like this a lot. I use it a lot. It's a medium to small size but it holds a lot."
        ],
        "helpful_votes": [
            "\n      One person found this helpful.\n    "
        ]
    }

现在你必须清理结果，从列表中删除它们，防止元素为空，我想你会得到你需要的。要得到所有的评论，你必须迭代页面，添加?pageNumber=1到链接，并迭代数字。你可以使用代理来防止IP阻塞，以防你要做很多请求。