That's the kind of thing I stumble across all the time. Indexing all the symbols in a codebase:

  results = Counter()
  for file in here.glob('*.py'):
      symbols = parse(file)
      results.update(symbols)

Scanning image metadata:

  for image in here.glob('*.png'):
      headers = png.Reader(image)
      ...

Now that I think about it, most of my use cases involve doing expensive things to all the files in a directory, but in ways where it'd be really sweet if I could do it all in the same process space instead of using a multiprocessing pool (which is otherwise an excellent way to skin that cat).

I've never let that stop me from getting the job done. There's always a way, and if we can't use tool A, then we'll make tool B work. It'll still be nice if it pans out that decent threading is at least an option.