Python String replace based on chars NOT in RegEx

Question

Is it possible to create a reqex that finds characters that are NOT is a specific set?

Rather than Blacklisting a bunch of characters and replacing them, it would be easier for me to allow a certain set and replace characters that are not in that set.

My set looks like this: [.a-zA-Z0-9]

I would like to do something like this:

clean_filename = re.sub(r'([.a-zA-Z0-9])', "_", filename)

obviously this code would replace the characters I want to keep, is there a way to replace the characters NOT in that set?

Answer 1

Yes, use the ^ negation "modifier": r'[^.a-zA-Z0-9]'

Answer 2

clean_filename = re.sub(r'[^.a-zA-Z0-9]', "_", filename)