Python：终止subprocess = Success，但它仍在运行（？）

Question

I have a simple script that calls another python script as a subprocess. I can confirm the subprocess is started and I can grab its PID.

When I attempt to terminate the subprocess (in win), I get the SUCCESS message against the correct PID, but Windows task manager shows the 2nd python.exe process to still be running.

Any suggestions to accomplish this task in Win? I'll be extending this to also work in OSX and Linux eventually:

Simplified:

#!/usr/bin/env python

import os, sys
import subprocess
from subprocess import Popen, PIPE, STDOUT, check_call

pyTivoPath="c:\pyTivo\pyTivo.py"

print "\nmyPID: %d" % os.getpid()

## Start pyTivo ##
py_process = subprocess.Popen(pyTivoPath, shell=True, stdout=PIPE, stderr=subprocess.STDOUT)
print "newPID: %s" % py_process.pid

## Terminate pyTivo ##  
#py_process.terminate() - for nonWin (?)
py_kill = subprocess.Popen("TASKKILL /PID "+ str(py_process.pid) + " /f") 

raw_input("\nPress Enter to continue...")

Note: Python2.7 required, psutils not available

Answer 1

Use the /F (Force) switch on the TASKKILL command. Lots of windows commands do not has useful return values. Don't recall if TASKKILL returns has a useful value.

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Sorry, overlooked your /F

You could try calling the win32 api directly.

import win32api
win32api.TerminateProcess(int(process._handle), -1)

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Found the ActiveState page for this. Documents a number of kill methods, including the Win32 approach above.

There are also a number of reasons why Windows will not allow you to terminate a process. Common reasons are permissions and buggy drivers that have pending I/O requests that don't response to the kill signal properly.

There are some programs, eg ProcessHacker, that are more enthusiastic about killing processes, but I don't know the technical details for certain, though I suspect forced closing of open file handles etc. and then calling Terminate are involved.

You can have similar issues on Linux, ie, no permission to kill process or the process is ignoring the kill signal. Easier to resolve on Linux though, if kill -9 does not work, it can't be killed and it is a rarer condition because you have to ignore signal 9 explicitly in your code.

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0) You could use TASKKILL /T to kill CMD and the Python interpreter.

1) If you change your process creation to create the python process directly (instead of invoking the .py and relying on cmd to launch) with the script name as command argument you will get the PID you expect when you create the process.

2) You could use TASKKILL /IM to kill the process by name, but the name will be the python interpreter and it could kill unintended processes.

Answer 2

In my implementation, the following actually creates TWO processes in Windows ("cmd.exe" and "python.exe").

py_process = subprocess.Popen(pyTivoPath, shell=True, stdout=PIPE, stderr=subprocess.STDOUT)

Noticing the "python.exe" process is a child of the "cmd.exe" process, I added the "/T" (tree kill) switch to my TASKKILL:

py_kill = subprocess.Popen("TASKKILL /PID "+ str(py_process.pid) + " /f /t") 

This results in the desired effect to effectively KILL the python subprocess.

Answer 3

Two processes are created because you call Popen with shell=True . It looks like the only reason you need to use a shell is so you make use of the file association with the interpreter. To resolve your issue you could also try:

from subprocess Popen, PIPE, STDOUT

pyTivoPath = "c:\pyTivo\pyTivo.py"
cmd = r'c:\Python27\python.exe "{}"'.format(pyTivoPath)

# start process
py_process = Popen(cmd, stdout=PIPE, stderr=STDOUT)

# kill process
py_process.terminate()