使用lxml的Python脚本，xpath返回空列表

Question

I tried to scrap href links from an html tag using xpath with lxml. But the xpath is returning null list whereas it was tested separately and it seems to work.

The code is returning a null value whereas the xpath seems to work fine.

page = self.opener.open(link).read()
doc=html.fromstring(str(page))
ref = doc.xpath('//ul[@class="s-result-list s-col-1 s-col-ws-1 s-result-list-hgrid s-height-equalized s-list-view s-text-condensed s-item-container-height-auto"]/li/div/div[@class="a-fixed-left-grid"]/div/div[@class="a-fixed-left-grid-col a-col-left"]/div/div/a')
for post in ref:
    print(post.get("href"))

I'm using a proxy server, for accessing the links and it seems to work, as the "doc" variable is getting populated with the html content. I've checked the links and I'm on the proper page to fetch this xpath.

This is the link from which I'm trying to fetch data: https://www.amazon.com/s/ref=lp_266162_nr_n_0?fst=as%3Aoff&rh=n%3A283155%2Cn%3A%211000%2Cn%3A1%2Cn%3A173508%2Cn%3A266162%2Cn%3A3564986011&bbn=266162&ie=UTF8&qid=1550120216&rnid=266162

Answer 1

Your xpath selector is invalid. try css selctor like below

import requests
import lxml, lxml.html

url = 'https://www.amazon.com/s/ref=lp_266162_nr_n_0?fst=as%3Aoff&rh=n%3A283155%2Cn%3A%211000%2Cn%3A1%2Cn%3A173508%2Cn%3A266162%2Cn%3A3564986011&bbn=266162&ie=UTF8&qid=1550120216&rnid=266162'
r = requests.get(url)
html = lxml.html.fromstring(r.content)
links = html.cssselect('.a-fixed-left-grid-col .a-col-left a')
for link in links:
    print(link.attrib['href'])

output

https://www.amazon.com/Top-500-Instant-Pot-Recipes/dp/1730885209
https://www.amazon.com/Monthly-Budget-Planner-Organizer-Notebook/dp/1978202865
https://www.amazon.com/Edge-Order-Daniel-Libeskind/dp/045149735X
https://www.amazon.com/Man-Glass-House-Johnson-Architect/dp/0316126438
https://www.amazon.com/Versailles-Private-Invitation-Guillaume-Picon/dp/2080203371
https://www.amazon.com/Palm-Springs-Modernist-Tim-Street-Porter/dp/0847861872
https://www.amazon.com/Building-Chicago-Architectural-John-Zukowsky/dp/0847848701
https://www.amazon.com/Taverns-American-Revolution-Adrian-Covert/dp/160887785X
https://www.amazon.com/TRAVEL-MOSAIC-Color-Number-Relaxation/dp/1717562221
https://www.amazon.com/Understanding-Cemetery-Symbols-Historic-Graveyards/dp/1547047216
https://www.amazon.com/Soviet-Bus-Stops-Christopher-Herwig/dp/099319110X
https://www.amazon.com/Famous-Movie-Scenes-Dot-Dot/dp/1977747043

pip requirements

certifi==2018.11.29
chardet==3.0.4
cssselect==1.0.3
idna==2.8
lxml==4.3.1
requests==2.21.0
urllib3==1.24.1

Answer 2

I suppose you are after the links within Books : Arts & Photography : Architecture : Buildings : Landmarks & Monuments . I used xpath within the script to fetch the links. Give it a go:

import requests
from lxml.html import fromstring

link = 'https://www.amazon.com/s/ref=lp_266162_nr_n_0?fst=as%3Aoff&rh=n%3A283155%2Cn%3A%211000%2Cn%3A1%2Cn%3A173508%2Cn%3A266162%2Cn%3A3564986011&bbn=266162&ie=UTF8&qid=1550120216&rnid=266162'
r = requests.get(link,headers={"User-Agent":"Mozilla/5.0"})
htmlcontent = fromstring(r.text)
itemlinks = htmlcontent.xpath('//*[@id="mainResults"]//*[contains(@class,"s-access-detail-page")]')
for link in itemlinks:
    print(link.get('href'))

If you wanted to go for css selector, then the following should work:

'#mainResults .s-access-detail-page'