Re: Trapping the segfault of a subprocess.Popen
On Apr 7, 1:58 am, Nobody nob...@nowhere.com 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 tjre...@udel.edu 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
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: Logging exceptions to a file
On May 7, 5:32 am, Lie Ryan lie.1...@gmail.com 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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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.
--
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
