Glad you find it useful. Below is an example script to demonstrate the concept. It is awesomely powerful. In vim, select some text and do this:

  :'<,'>! ./example.py

  #!/bin/env python3
  #:'<,'>! ./example.py # ← this is how to use it
  import sys
  data = sys.stdin.readlines()
  for l in data:
    l = l.replace("a", "e").rstrip()
    print(l)