I'd like to take care of this at Python.  At least for posix (someone else can deal with the windows side if they want).

I just stumbled upon an extension module at work that someone wrote specifically because os.listdir consumed way too much ram by building up a huge list on large directories with tons of long filenames that it needed to process.  (when your process is in charge of keeping that directory in check... the inability to process it once it grows too large simply isn't acceptable)