Python Xpath：lxml.etree.XPathEvalError：谓词无效

Question

I'm trying to learn how to scrape web pages and in the tutorial I'm using the code below is throwing this error:

lxml.etree.XPathEvalError: Invalid predicate

The website I'm querying is (don't judge me, it was the one used in the training vid :/ ): https://itunes.apple.com/us/app/candy-crush-saga/id553834731

The xpath string that causes the error is here:

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

I'm using the LXML and requests libraries.

If you need any additional info I'm happy to provide!

Answer 1

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

You were missing a closing ] after "center-stack" .

You can also just pull the a[@class="name"] tags from div[@class="content"]

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

Both will give you the hrefs you want:

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']