pythonhtmlalgorithmxhtml

How do I fix wrongly nested / unclosed HTML tags?


I need to sanitize HTML submitted by the user by closing any open tags with correct nesting order. I have been looking for an algorithm or Python code to do this but haven't found anything except some half-baked implementations in PHP, etc.

For example, something like

<p>
  <ul>
    <li>Foo

becomes

<p>
  <ul>
    <li>Foo</li>
  </ul>
</p>

Any help would be appreciated :)


Solution

  • using BeautifulSoup:

    from BeautifulSoup import BeautifulSoup
    html = "<p><ul><li>Foo"
    soup = BeautifulSoup(html)
    print soup.prettify()
    

    gets you

    <p>
     <ul>
      <li>
       Foo
      </li>
     </ul>
    </p>
    

    As far as I know, you can't control putting the <li></li> tags on separate lines from Foo.

    using Tidy:

    import tidy
    html = "<p><ul><li>Foo"
    print tidy.parseString(html, show_body_only=True)
    

    gets you

    <ul>
    <li>Foo</li>
    </ul>
    

    Unfortunately, I know of no way to keep the <p> tag in the example. Tidy interprets it as an empty paragraph rather than an unclosed one, so doing

    print tidy.parseString(html, show_body_only=True, drop_empty_paras=False)
    

    comes out as

    <p></p>
    <ul>
    <li>Foo</li>
    </ul>
    

    Ultimately, of course, the <p> tag in your example is redundant, so you might be fine with losing it.

    Finally, Tidy can also do indenting:

    print tidy.parseString(html, show_body_only=True, indent=True)
    

    becomes

    <ul>
      <li>Foo
      </li>
    </ul>
    

    All of these have their ups and downs, but hopefully one of them is close enough.