This is a simple, one-purpose python library that spawns a process with a shell command an allows you to concurrently feed data into its stdin, while being able to read its stdout and check its status.
Python's subprocess library is very powerful. Yet, simply starting a server program that continuously reads from standard input remained surprisingly elusive. Eventually, as I found myself delving into the mysteries of process groups to properly kill a zombie process, making repeated calls to flush in an act of naked desperation trying to get output without blocking my whole program, and being unable to query the status of my subprocess without wrestling with byzantine return code policies, I finally gave up. The subprocess API seemed to fight me at every turn. I realized that subprocess was simply not designed for my use case.
That's when I made feedwater.
If you
- want to invoke another program from your python script that reads from standard input and has an indefinite lifecycle
- want to sometimes pass data to said program
- want to query it's output in a non-blocking way
- want occasionally to query its status
- want to be able to kill it and all child processes it may or may not have spawned
then feedwater may be for you.