Python subprocess.call thread hang, subprocess.popen no hang

Question

I am trying to automate the installation of a specific program using Sikuli and scripts on Windows 7. I needed to start the program installer and then used Siluki to step through the rest of the installation. I did this using Python 2.7

This code works as expected by creating a thread, calling the subprocess, and then continuing the main process:

import subprocess
from threading import Thread

class Installer(Thread):
  def __init__(self):
    Thread.__init__(self)
  def run(self):
    subprocess.Popen(["msiexec", "/i", "c:\path\to\installer.msi"], shell=True)

i = Installer()
i.run()
print "Will show up while installer is running."
print "Other things happen"

i.join()

This code does not operate as desired. It will start the installer but then hang:

import subprocess
from threading import Thread

class Installer(Thread):
  def __init__(self):
    Thread.__init__(self)
  def run(self):
    subprocess.call("msiexec /i c:\path\to\installer.msi")

i = Installer()
i.run()
print "Will not show up while installer is running."
print "Other things happen"

i.join()

I understand that subprocess.call will wait for the process to terminate. Why does that prevent the main thread from continuing on? Should the main continue execution immediately after the process call?

Why is there such a difference in behaviors?

I have only just recently started using threads C.

Maybe admin privileges are the problem. Try subprocess.call(['runas', '/user:Administrator', 'c:\path\to\installer.msi']) — Piotr Dabkowski, Apr 08 '14 at 21:04
do you need to add the command line parameters to your install command to make it a silent install? — Rusty Weber, Apr 08 '14 at 21:22

score 1 · Accepted Answer · answered Apr 08 '14 at 21:35

1

You're calling i.run(), but what you should be calling is i.start(). start() invokes run() in a separate thread, but calling run() directly will execute it in the main thread.

answered Apr 08 '14 at 21:35

dano

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I will make sure it is using i.start() and see how that works. – houckrj Apr 09 '14 at 11:04
Your suggestion was correct. When I used i.start() instead of i.run(), subprocess.call worked properly. – houckrj Apr 10 '14 at 12:30

score 0 · Answer 2 · edited May 23 '17 at 12:21

0

First.

you need to add the command line parameters to your install command to make it a silent install.. http://msdn.microsoft.com/en-us/library/aa372024%28v=vs.85%29.aspx the subprocess is probably hung waiting for an install process that will never end because it is waiting for user input.

Second.

if that doesn't work.. you should be using popen and communicate How to use subprocess popen Python

Third.

if that still didn't work, your installer is hanging some where and you should debug the underlying process there.

edited May 23 '17 at 12:21

Community

1
1

answered Apr 08 '14 at 21:26

Rusty Weber

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I will look for the silent install command parameters. That would make the process easier. – houckrj Apr 09 '14 at 11:05
The silent command for the install worked well and helped with the overall execution of the program. – houckrj Apr 10 '14 at 12:31

Python subprocess.call thread hang, subprocess.popen no hang

2 Answers2