Bleach is an HTML sanitizing library that escapes or strips markup and attributes based on a white list. Bleach can also linkify text safely, applying filters that Django's urlize filter cannot, and optionally setting rel attributes, even on links already in the text.
Bleach is intended for sanitizing text from untrusted sources. If you find yourself jumping through hoops to allow your site administrators to do lots of things, you're probably outside the use cases. Either trust those users, or don't.
Because it relies on html5lib, Bleach is as good as modern browsers at dealing with weird, quirky HTML fragments. And any of Bleach's methods will fix unbalanced or mis-nested tags.
The simplest way to use Bleach is:
>>> import bleach >>> bleach.clean('an <script>evil()</script> example') u'an <script>evil()</script> example' >>> bleach.linkify('an http://example.com url') u'an <a href="http://example.com" rel="nofollow">http://example.com</a> url
NB: Bleach always returns a unicode object, whether you give it a bytestring or a unicode object, but Bleach does not attempt to detect incoming character encodings, and will assume UTF-8. If you are using a different character encoding, you should convert from a bytestring to unicode before passing the text to Bleach.