How do you run a Python script as a service in Windows?

Question

I am sketching the architecture for a set of programs that share various interrelated objects stored in a database. I want one of the programs to act as a service which prov

Answer 1

A complete pywin32 example using loop or subthread

After working on this on and off for a few days, here is the answer I would have wished to find, using pywin32 to keep it nice and self contained.

This is complete working code for one loop-based and one thread-based solution. It may work on both python 2 and 3, although I've only tested the latest version on 2.7 and Win7. The loop should be good for polling code, and the tread should work with more server-like code. It seems to work nicely with the waitress wsgi server that does not have a standard way to shut down gracefully.

I would also like to note that there seems to be loads of examples out there, like this that are almost useful, but in reality misleading, because they have cut and pasted other examples blindly. I could be wrong. but why create an event if you never wait for it?

That said I still feel I'm on somewhat shaky ground here, especially with regards to how clean the exit from the thread version is, but at least I believe there are nothing misleading here.

To run simply copy the code to a file and follow the instructions.

update:

Use a simple flag to terminate thread. The important bit is that "thread done" prints.
For a more elaborate example exiting from an uncooperative server thread see my post about the waitress wsgi server.

# uncomment mainthread() or mainloop() call below
# run without parameters to see HandleCommandLine options
# install service with "install" and remove with "remove"
# run with "debug" to see print statements
# with "start" and "stop" watch for files to appear
# check Windows EventViever for log messages

import socket
import sys
import threading
import time
from random import randint
from os import path

import servicemanager
import win32event
import win32service
import win32serviceutil
# see http://timgolden.me.uk/pywin32-docs/contents.html for details


def dummytask_once(msg='once'):
    fn = path.join(path.dirname(__file__),
                '%s_%s.txt' % (msg, randint(1, 10000)))
    with open(fn, 'w') as fh:
        print(fn)
        fh.write('')


def dummytask_loop():
    global do_run
    while do_run:
        dummytask_once(msg='loop')
        time.sleep(3)


class MyThread(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        global do_run
        do_run = True
        print('thread start\n')
        dummytask_loop()
        print('thread done\n')

    def exit(self):
        global do_run
        do_run = False


class SMWinservice(win32serviceutil.ServiceFramework):
    _svc_name_ = 'PyWinSvc'
    _svc_display_name_ = 'Python Windows Service'
    _svc_description_ = 'An example of a windows service in Python'

    @classmethod
    def parse_command_line(cls):
        win32serviceutil.HandleCommandLine(cls)

    def __init__(self, args):
        win32serviceutil.ServiceFramework.__init__(self, args)
        self.stopEvt = win32event.CreateEvent(None, 0, 0, None)  # create generic event
        socket.setdefaulttimeout(60)

    def SvcStop(self):
        servicemanager.LogMsg(servicemanager.EVENTLOG_INFORMATION_TYPE,
                            servicemanager.PYS_SERVICE_STOPPED,
                            (self._svc_name_, ''))
        self.ReportServiceStatus(win32service.SERVICE_STOP_PENDING)
        win32event.SetEvent(self.stopEvt)  # raise event

    def SvcDoRun(self):
        servicemanager.LogMsg(servicemanager.EVENTLOG_INFORMATION_TYPE,
                            servicemanager.PYS_SERVICE_STARTED,
                            (self._svc_name_, ''))
        # UNCOMMENT ONE OF THESE
        # self.mainthread()
        # self.mainloop()

    # Wait for stopEvt indefinitely after starting thread.
    def mainthread(self):
        print('main start')
        self.server = MyThread()
        self.server.start()
        print('wait for win32event')
        win32event.WaitForSingleObject(self.stopEvt, win32event.INFINITE)
        self.server.exit()
        print('wait for thread')
        self.server.join()
        print('main done')

    # Wait for stopEvt event in loop.
    def mainloop(self):
        print('loop start')
        rc = None
        while rc != win32event.WAIT_OBJECT_0:
            dummytask_once()
            rc = win32event.WaitForSingleObject(self.stopEvt, 3000)
        print('loop done')


if __name__ == '__main__':
    SMWinservice.parse_command_line()