["python","filenames","slug","sanitize"]
Turn a string into a valid filename?

I have a string that I want to use as a filename, so I want to remove all characters that wouldn't be allowed in filenames, using Python. I'd rather be strict than otherwise, so let's say I want to retain only letters, digits, and a small set of other characters like "_-.() ". What's the most elegant solution? The filename needs to be valid on multiple operating systems (Windows, Linux and Mac OS) - it's an MP3 file in my library with the song title as the filename, and is shared and backed up between 3 machines.
You can look at the Django framework (but take their licence into account!) for how they create a "slug" from arbitrary text. A slug is URL- and filename- friendly. The Django text utils define a function, slugify(), that's probably the gold standard for this kind of thing. Essentially, their code is the following. import unicodedata import re def slugify(value, allow_unicode=False): """ Taken from https://github.com/django/django/blob/master/django/utils/text.py Convert to ASCII if 'allow_unicode' is False. Convert spaces or repeated dashes to single dashes. Remove characters that aren't alphanumerics, underscores, or hyphens. Convert to lowercase. Also strip leading and trailing whitespace, dashes, and underscores. """ value = str(value) if allow_unicode: value = unicodedata.normalize('NFKC', value) else: value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii') value = re.sub(r'[^\w\s-]', '', value.lower()) return re.sub(r'[-\s]+', '-', value).strip('-_') And the older version: def slugify(value): """ Normalizes string, converts to lowercase, removes non-alpha characters, and converts spaces to hyphens. """ import unicodedata value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore') value = unicode(re.sub('[^\w\s-]', '', value).strip().lower()) value = unicode(re.sub('[-\s]+', '-', value)) # ... return value There's more, but I left it out, since it doesn't address slugification, but escaping.