Python slugify function

I often need to transform a string to something usable in a URL. Over the years I’ve used this snippet a bunch to do just that:

>>> import re
>>> def slugify(s):
...   s = re.sub('[^\w\s-]', '', s)
...   s = re.sub('[\s-]+', '-', s)
...   return s.lower().strip('-')
>>> slugify(" Hello  World - and, this'   shows? ALL. the neat (<stuff>) that slugify can do! ")

(nb: “slug” is a a newspaper term that is much used throughout Django, the web framework I cut my teeth on. As a concept, it maps very nicely to URLs).

The thing I like most about this snippet is 2/3 of the function body is about removing characters instead of adding/replacing them.

Like if the input string already has a dash, it removes it before going any further.

If, after the first line, there is one or more dashes in a row, it collapses them into a single dash.

This all results in a very clean output.