的Python的XPath：lxml.etree.XPathEvalError：無效的謂詞

Question

我想學習如何刮網頁，並在教程中，我使用下面的代碼引發此錯誤：

lxml.etree.XPathEvalError: Invalid predicate 

網站我查詢時（不要對我做出判斷，這是在訓練VID使用的一個：/）：https://itunes.apple.com/us/app/candy-crush-saga/id553834731

導致錯誤的XPath字符串是在這裏：

links = tree.xpath('//div[@class="center-stack"//*/a[@class="name"]/@href') 

我使用LXML和請求庫。

如果您需要任何其他信息，我很樂意提供！

Answer 1

print(tree.xpath('//div[@class="center-stack"]//*/a[@class="name"]/@href')) 

你是缺少一個右"center-stack"後]。

你也可以拉a[@class="name"]標籤從div[@class="content"]

tree.xpath('//div[@class="content"]//a[@class="name"]/@href') 

都將給你的HREFs你想：

In [19]: import requests 

In [20]: from lxml.html import fromstring 


In [21]: r = requests.get("https://itunes.apple.com/us/app/candy-crush-saga/id553834731") 

In [22]: tree = fromstring(r.content) 

In [23]: a = tree.xpath('//div[@class="content"]//a[@class="name"]/@href') 

In [24]: b = tree.xpath('//div[@class="center-stack"]//*/a[@class="name"]/@href') 

In [25]: print(a == b) 
True 

In [26]: print(a) 
['https://itunes.apple.com/us/app/word-search-puzzles/id609067187?mt=8', 'https://itunes.apple.com/us/app/cookie-jam/id727296976?mt=8', 'https://itunes.apple.com/us/app/jewel-mania/id561326449?mt=8', 'https://itunes.apple.com/us/app/jelly-splash/id645949180?mt=8', 'https://itunes.apple.com/us/app/bubble-island/id531354582?mt=8'] 

In [27]: print(b) 
['https://itunes.apple.com/us/app/word-search-puzzles/id609067187?mt=8', 'https://itunes.apple.com/us/app/cookie-jam/id727296976?mt=8', 'https://itunes.apple.com/us/app/jewel-mania/id561326449?mt=8', 'https://itunes.apple.com/us/app/jelly-splash/id645949180?mt=8', 'https://itunes.apple.com/us/app/bubble-island/id531354582?mt=8']