问题
I am using lxml and I have a scrapped page from Google Scholar. Following is a minimal working example and things I have tried.
In [56]: seed = "https://scholar.google.com/citations?view_op=search_authors&hl=en&mauthors=label:machine_learning"
In [60]: page = urllib2.urlopen(seed).read()
In [63]: tree = html.fromstring(page)
In [64]: xpath = '(/html/body/div[1]/div[4]/div[2]/div/span/button[2]/@onclick)[1]'
In [65]: tree.xpath(xpath)
#first element returns as list
Out[65]: ["window.location='/citations?view_op\\x3dsearch_authors\\x26hl\\x3den\\x26oe\\x3dASCII\\x26mauthors\\x3dlabel:machine_learning\\x26after_author\\x3dVCoCALPY_v8J\\x26astart\\x3d10'"]
In [66]: xpath = '(/html/body/div[1]/div[4]/div[2]/div/span/button[2]/@onclick)[2]'
#there is no second element
In [67]: tree.xpath(xpath)
Out[67]: []
In [70]: xpath = '(/html/body/div[1]/div[4]/div[2]/div/span/button[2]/@onclick)'
#The list contains only one element
In [71]: tree.xpath(xpath)
Out[71]: ["window.location='/citations?view_op\\x3dsearch_authors\\x26hl\\x3den\\x26oe\\x3dASCII\\x26mauthors\\x3dlabel:machine_learning\\x26after_author\\x3dVCoCALPY_v8J\\x26astart\\x3d10'"]
As per documentation here, return values can be smart strings, but I cannot get a string output from xpath function. How can I write the xpath so that I get a string output from xpath
回答1:
You can use an XPath expression string(/html/body/div[1]/div[4]/div[2]/div/span/button[2]/@onclick), in that case you get a simple string value.
来源：https://stackoverflow.com/questions/34461840/force-xpath-to-return-a-string-lxml