test bs4.py

from bs4 import BeautifulSoup
soup = BeautifulSoup("<p>Some<b>bad<i>HTML")
print(soup.prettify())
html
 body
  <p>
   Some
   <b>
    bad
    <i>
     HTML
    </i>
   </b>
  </p>
 </body>
</html>
soup.find(text="bad")
'bad'
soup.i
<i>HTML</i>
#
>>> soup = BeautifulSoup("<tag1>Some<tag2/>bad<tag3>XML", "xml")
#
>>> print(soup.prettify())
<?xml version="1.0" encoding="utf-8"?>
<tag1>
 Some
 <tag2/>
 bad
 <tag3>
  XML
 </tag3>
</tag1>