Question

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 🙂

Answer 1

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.