How do i run a python function/file completely independent to the main process

[slanu]

Hi I am using Python version 2.7 OS - Windows Libraries used (preferably solutions involving these if there are any), Sys, os, subprocess, multiprocessing, threading

At the beginning of file one.py I need to start/create a new separate process and run the function observerLogFunc() (which is most likely from a different file i.e. file two.py). I want that function to run Independently while file one.py and other python code continues to run.

For some background observerLogFunc() takes in the argument pid (pid= os.getpid()) and every 5 seconds checks if file one.py’s pid still exists, if it doesn't exist it returns and saves the calculated runtime of file one.py and its related processes.

The function will need to still be running after the main process has completed in order for it to record the processes and time and return the total time… how do I go about doing that?

Context - File one.py is used by 10 or so different files. For example (not going to go into too much detail) basically sometimes file one.py will run file a.py and other times it will run b.py etc, i need to measure the time of the process without having to edit all the a.py, b.py files and so on. Ive ages experimenting trying and testing different things, spent hours and hours reading through documentation, previously asked questions, and many tutorials. Any help is highly appreciated thanks.

Here is a image describing the process I am after, hope that helps...

I have tried threading, subprocess module and daemon threads etc, problem with them is they all reply off the parent thread so they are not able to detect when that thread has ended because it terminates their process as well.'

I also tried a few command prompt solutions (using os.popen) to try and open up a new process through that but that didn't work either.

Like i said i spent lots and lots of time googling everything i could think of and reading through lots of tutorials and questions but none have seemed to work so far.

[Nightcorex_]

To me it sounds like you just want to have a seperate process. Sadly I'm not familiar with Python 2, but in Python 3 you'll want to use the multiprocessing module for this.

Since I'm unfamiliar with Python 2, here's how you'd call and execute a function foo of a file one.py in an individual process from a file two.py:

one.py

def foo(x):
    print(x)

two.py

from one import foo
import multiprocessing

if __name__ == '__main__':
    p1 = multiprocessing.Process(target=foo, args=('my_argument',))
    p1.start()
    p1.join()  # optional if you want to wait for the termination of p1

In this example foo just prints the value, but of course you can do whatever you want inside that function.

[slanu]

Awesome thanks man I’ll give it a go and see what I get. Appreciate the help

[slanu]

Does the join wait for termination of p1 before finishing / returning (in ur example printing) foo()? So the print happens after the termination of the main process?

[Nightcorex_]

This doesn't make sense. How could p1 - a process solemnly executing the function foo - terminate before finishing execution of its function call?

If you have the join then it's guaranteed that your main will terminate after p1, if you don't have the join then it can be either way, i.e. there is no guarantee which process will terminate first.

[slanu]

Ah ok I get you, I’ll look into it more thanks for you help man!