如何在 python 中转义字符串以用作 xpath 密钥

Question

I got this key error in python

  KeyError: ("./note/[@player='Ba'g']",)

when using

  player = "Ba'g"
  xpathstring = "./note/[@player='{}']".format(player.replace("'","\'"))
  p = xmltree.find(xpathstring)

So I am wondering how to escape the string such that I can use as an xpath search string in an xmltree

Answer 1

Currently you are passing the string "./note/[@player='Ba'g']" to the find function.

There seems to be no way to properly escape single quotes in xpath .

However, you can switch from single to double quotes. Try:

 xpathstring = "./note/[@player=\"{}\"]".format(player)

This is the suggested solution in the linked issue.

Answer 2

I propose this workaround (XPath 2.0):

Assuming you have an element with an attribute which contains single and double quotation marks:

<div>
<note player="Ba&apos;g&quot;N Toast">foo</note>
</div>

To select this node with XPath and a fixed variable we can use something like:

import  re
player = '''Ba'g"N Toast'''
result = re.sub(r"(.+)", r"'\1'",player.replace("'","',codepoints-to-string(39),'").replace('"',"',codepoints-to-string(34),'"))
xpathstring = "//note[@player=concat({})]".format(result)
p = xmltree.find(xpathstring)

We replace ' and " with their codepoints equivalents. The result will feed the concat function in the XPath expression.