Spawn a long-lived process outside of PSS/E

child.py

"""
Child thread

constantly writes to a file for 60 seconds
"""
from __future__ import with_statement
import time

FILE = 'demo.txt'

def child():
    print 'running child'

    with open(FILE, 'w') as demo:
        demo.write('BEGIN\n')

    for i in range(60):
        time.sleep(1)
        with open(FILE, 'a') as demo:
            demo.write('%d\n' % time.time())

child()

main.py

"""
Main thread

Spawns a new process outside of itself.
"""
import subprocess
from tkFileDialog import askopenfilename

def main():

    childscript = askopenfilename(title="Run which script?")

    subprocess.Popen(
            ["python", childscript],
            creationflags=subprocess.CREATE_NEW_CONSOLE)

    print "finished main"

main()