I have a python script invoked with Python 2.7.15 spawning another python script using Python 3.8.5, so it matches your scenario. Print('Runner started! Runner output follows.')įor line in iter(p.stdout.readline, b''):Īnd the current time from runner.py will be displayed in the executor.py script:Ĭode: Select all Aaron% python executor.py

P = Popen(, stdout=PIPE, bufsize=1) # Note the '-u' flag. Read the standard output and error, using non-blocking connections Poll the. My demo below works with the '-u' and it does nothing at all without the flag.Ĭode: Select all Aaron% cat runner.pyĬode: Select all Aaron% cat executor.py Features Start system processes in the background and find their process id. It appears that you need to tell the spawned python process to not buffer its output by passing the '-u' flag. Maybe this will point you in the right direction or at least make you aware of the subprocess module if you haven't heard of it. Here is a snippet taken from one of the examples where you can write to the stdin of the spawned process (you can do something similar for reading from stdout as well):Ĭode: Select all proc = subprocess.Popen(, stdin=subprocess.PIPE) It covers writing to and reading from stdin and stdout of a subprocess: This is the Python 2.7 documentation for the subprocess module: Īnd I think this site has a great writeup with some examples on using the module. You can spawn a new process from Python 2.7 code (to run your Python 3 script) and set it up such that the stdin and stdout can be read and written to. I don't have any of my own examples I can provide, but are you familiar with the subprocess module in Python? It sounds like that may be what you want.

Python run subprocess in background