Trapping the segfault of a subprocess.Popen
All, I need to run a third-party binary from a python script and retrieve its output (and its error messages). I use something like >>> process = subprocess.Popen(options, stdout=subprocess.PIPE, >>> stderr=subprocess.PIPE) >>> (info_out, info_err) = process.communicate() That works fine, except that the third-party binary in question doesn't behave very nicely and tend to segfaults without returning any error. In that case, `process.communicate` hangs for ever. I thought about calling a `threading.Timer` that would call `process.terminate` if `process.wait` doesn't return after a given time... But it's not really a solution: the process in question can sometimes take a long time to run, and I wouldn't want to kill a process still running. I also thought about polling every x s and stopping when the result of a subprocess.Popen(["ps","-p",str(initialprocess.pid)], stdout=subprocess.PIPE) becomes only the header line, but my script needs to run on Windows as well (and no ps over there)... Any suggestion welcome, Thx in advance P. -- http://mail.python.org/mailman/listinfo/python-list
Re: Trapping the segfault of a subprocess.Popen
On Apr 7, 1:58 am, Nobody wrote: > On Wed, 06 Apr 2011 02:20:22 -0700, Pierre GM wrote: > > I need to run a third-party binary from a python script and retrieve > > its output (and its error messages). I use something like > >>>> process = subprocess.Popen(options, stdout=subprocess.PIPE, > > stderr=subprocess.PIPE) > >>>> (info_out, info_err) = process.communicate() > > That works fine, except that the third-party binary in question doesn't > > behave very nicely and tend to segfaults without returning any error. In > > that case, `process.communicate` hangs for ever. > > Odd. The .communicate method should return once both stdout and stderr > report EOF and the process is no longer running. Whether it terminates > normally or on a signal makes no difference. > > The only thing I can think of which would cause the situation which you > describe is if the child process spawns a child of its own before > terminating. In that case, stdout/stderr won't report EOF until any > processes which inherited them have terminated. I think you nailed it. Running the incriminating command line in a terminal doesn't return to the prompt. In fact, a ps shows that the process is sleeping in the foreground. Guess I should change the subject of this thread... > > I thought about calling a `threading.Timer` that would call > > `process.terminate` if `process.wait` doesn't return after a given > > time... But it's not really a solution: the process in question can > > sometimes take a long time to run, and I wouldn't want to kill a > > process still running. > > I also thought about polling every x s and stopping when the result of > > a subprocess.Popen(["ps","-p",str(initialprocess.pid)], > > stdout=subprocess.PIPE) becomes only the header line, but my script > > needs to run on Windows as well (and no ps over there)... > > It should suffice to call .poll() on the process. In case that doesn't > work, the usual alternative would be to send signal 0 to the process (this > will fail with ESRCH if the process doesn't exist and do nothing > otherwise), e.g.: > > import os > import errno > > def exists(process): > try: > os.kill(process.pid, 0) > except OSError, e: > if e.errno == errno.ESRCH: > return False > raise > return True OK, gonna try that, thx. > You might need to take a different approach for Windows, but the above is > preferable to trying to parse "ps" output. Note that this only tells you > if /some/ process exists with the given PID, not whether the original > process exists; that information can only be obtained from the Popen > object. -- http://mail.python.org/mailman/listinfo/python-list
Re: Trapping the segfault of a subprocess.Popen
On Apr 7, 5:12 am, Terry Reedy wrote: > On 4/6/2011 7:58 PM, Nobody wrote: > > > On Wed, 06 Apr 2011 02:20:22 -0700, Pierre GM wrote: > > >> I need to run a third-party binary from a python script and retrieve > >> its output (and its error messages). I use something like > >>>>> process = subprocess.Popen(options, stdout=subprocess.PIPE, > >> stderr=subprocess.PIPE) > >>>>> (info_out, info_err) = process.communicate() > >> That works fine, except that the third-party binary in question doesn't > >> behave very nicely and tend to segfaults without returning any error. In > >> that case, `process.communicate` hangs for ever. > > I am not sure this will help you now, but > Victor Stinner has added a new module to Python 3.3 that tries to catch > segfaults and other fatal signals and produce a traceback before Python > disappears. Unfortunately, I'm limited to Python 2.5.x for this project. But good to know, thanks... -- http://mail.python.org/mailman/listinfo/python-list
Re: what is wrong with my python code?
On Wednesday 07 February 2007 12:43:34 Dongsheng Ruan wrote: > I got feed back saying" list object is not callable". But I can't figure > out what is wrong with my code. > for i in range(l): > print A(i) You're calling A, when you want to access one of its elements: use the straight brackets [ for i in range(l): print A[i] -- http://mail.python.org/mailman/listinfo/python-list
Logging exceptions to a file
All,
I need to log messages to both the console and a given file. I use the
following code (on Python 2.5)
>>> import logging
>>> #
>>> logging.basicConfig(level=logging.DEBUG,)
>>> logfile = logging.FileHandler('log.log')
>>> logfile.setLevel(level=logging.INFO)
>>> logging.getLogger('').addHandler(logfile)
>>> #
>>> mylogger = logging.getLogger('mylogger')
>>> #
>>> mylogger.info("an info message")
So far so good, but I'd like to record (possibly unhandled) exceptions
in the logfile.
* Do I need to explicitly trap every single exception ?
* In that case, won't I get 2 log messages on the console (as
illustrated in the code below:
>>> try:
>>> 1/0
>>> except ZeroDivisionError:
>>> mylogger.exception(":(")
>>> raise
Any comments/idea welcomed
Cheers.
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Re: Logging exceptions to a file
On May 7, 5:32 am, Lie Ryan wrote:
> Pierre GM wrote:
> > All,
> > I need to log messages to both the console and a given file. I use the
> > following code (on Python 2.5)
>
> >>>> import logging
> >>>> #
> >>>> logging.basicConfig(level=logging.DEBUG,)
> >>>> logfile = logging.FileHandler('log.log')
> >>>> logfile.setLevel(level=logging.INFO)
> >>>> logging.getLogger('').addHandler(logfile)
> >>>> #
> >>>> mylogger = logging.getLogger('mylogger')
> >>>> #
> >>>> mylogger.info("an info message")
>
> > So far so good, but I'd like to record (possibly unhandled) exceptions
> > in the logfile.
> > * Do I need to explicitly trap every single exception ?
> > * In that case, won't I get 2 log messages on the console (as
> > illustrated in the code below:
> >>>> try:
> >>>> 1/0
> >>>> except ZeroDivisionError:
> >>>> mylogger.exception(":(")
> >>>> raise
>
> > Any comments/idea welcomed
> > Cheers.
>
> Although it is usually not recommended to use a catch-all except, this
> is the case where it might be useful. JUST DON'T FORGET TO RE-RAISE THE
> EXCEPTION.
>
> if __name__ == '__main__':
> try:
> main():
> except Exception, e:
> # log('Unhandled Exception', e)
> raise
OK for a simple script, but the (unhandled) exceptions need to be
caught at the module level. Any idea?
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