Escape unescaped data of XML string in python3

Question

I want to escape the unescaped data inside a xml string e.g.

string = "<tag parameter = "something">I want to escape these >, < and &</tag>"

to

"<tag parameter = "something">I want to escape these &gt;, &lt; and &amp;</tag>"

• Now, I definitely can't use any xml parsing libraries like xml.dom.minidom or xml.etree because the data is unescaped & will give error

• In regex, I figure out way to match & get start and end positions of data substing

  exp = re.search(">.+?</", label)
  # Get position of the data between tags
  start = exp.start() + 1
  end = exp.end() - 2
  return label[ : start] + saxutils.escape(label[start : end]) + label[end : ]
  

• But in re.search, I can't match the exact xml format

• If I use re.findall I can't get positions of the substrings found
• I could always find positions of found substring by index but that won't be efficient, I want a simple but efficent solution
• BeautifulSoup solutions are welcomed but I wish there was some more beautiful way to do it with python's basic libraries

Answer 1

Perhaps you should be considering re.sub:

>>> oldString = '<tag parameter = "something">I want to escape these >, < and &</tag>'
>>> newString = re.sub(r"(<tag.*?>)(.*?)</tag>", lambda m: m.group(1) + cgi.escape(m.group(2)) + "</tag>", oldString)
>>> print newString
<tag parameter = "something">I want to escape these &gt;, &lt; and &amp;</tag>

My warning is that the regular expression will definitely break if you have nested tags. See Why is it such a bad idea to parse XML with regex?