A slug is a URL-friendly version of a string, typically used in URLs to identify a resource. Slugs use only lowercase letters, numbers, and hyphens, and are often used to generate human-readable URLs.

In order to convert any string to a slug, you first need to use str.lower() and str.strip() to normalize the input string. Then, you can use re.sub() and regular expressions to replace spaces, dashes, and underscores with hyphens, and remove any special characters.

from re import sub

def slugify(s):
  s = s.lower().strip()
  s = re.sub(r'[^\w\s-]', '', s)
  s = re.sub(r'[\s_-]+', '-', s)
  s = re.sub(r'^-+|-+$', '', s)
  return s

slugify('Hello World!') # 'hello-world'