Rather than adding a new function, why not adding a parameter like sort(key=func, reverse=True)? Something like fnmatch.filterfalse(pat, invert=True)?

The Unix grep command has a --invert-match option:

       -v, --invert-match
              Invert the sense of matching, to select non-matching lines.

The Unix find and test commands use "!" to invert a condition. Example:

   find ! -name "*.py"  # list files which doesn't match ".py"
   test ! -e setup.py   # true if setup.py doesn't exist