Subprocess .wait() is not waiting

Ian Kelly ian.g.kelly at
Fri Mar 24 16:24:05 EDT 2017

On Fri, Mar 24, 2017 at 2:09 PM, Chris Angelico <rosuav at> wrote:
> On Sat, Mar 25, 2017 at 6:55 AM, adam.c.bernier <adam.c.bernier at> wrote:
>> On Friday, March 24, 2017 at 12:55:30 PM UTC-7, adam.c.bernier wrote:
>>> On Friday, March 24, 2017 at 12:51:02 PM UTC-7, Chris Angelico wrote:
>>> > On Sat, Mar 25, 2017 at 6:40 AM, Ian Kelly <ian.g.kelly at> wrote:
>>> > > If that's what's happening it would be a bug. Are you sure that the
>>> > > other program isn't simply crashing or otherwise failing to complete?
>>> > >
>>> >
>>> > Or possibly is running asynchronously. Is this a GUI app? A lot of
>>> > Windows GUI programs don't wait when you invoke them.
>>> >
>>> > ChrisA
>>> Aha! Since the Excel app is a GUI app it's not waiting is that right?
>> If that's the case is there any workaround?
> Errr.... been a while since I messed with Windows.... from memory, I
> think you can "start /wait programname" to make it wait?? Worth a try,
> at least.

start /wait is for batch scripts, specifically because by default
start doesn't wait on GUI programs. I'm pretty sure that
WaitForSingleObject (which Popen.wait uses) is perfectly capable of
waiting on GUI programs (I would even bet dollars for donuts that this
is exactly what start /wait does).

Another possibility is that the subprocess itself is creating its own
subprocesses and not waiting on them. If it terminates before its
children, the wait() call will finish even though work is still being

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