Re: [GRASS-dev] Python and delayed or missing stderr output
On Sun, Sep 9, 2018 at 9:47 PM Markus Metz wrote: > > > > On Wed, Sep 5, 2018 at 10:43 AM Markus Neteler wrote: > > > > Hi, > > > > AFAIK Python buffers (i.e. effectively delays) stderr output which is > > unhelpful in the GRASS GIS context. > > > > Searching for a solution, I found this reference: sys.stdout.flush() > > e.g. > > https://stackoverflow.com/questions/10019456/usage-of-sys-stdout-flush-method > > That should be > sys.stderr.flush() > right? > > Regarding python's multiprocessing, it makes sense that stderr is suppressed because you would not know which process process produced which stderr (or stdout) message. There must be a method in python to redirect stderr and stdout for each process to a unique file, otherwise it would not be possible to find out why some process failed. > > Such a method would need to be implemented in each module usings python's multiprocessing. maybe worth a try also with stderr: https://stackoverflow.com/questions/1501651/log-output-of-multiprocessing-process i.e. within the function that is the target of multiprocessing.Process sys.stderr = open(str(os.getpid()) + ".err.log", "w") and it seems to be a good idea to always sys.stderr.flush() at the end of the subprocess Markus M ___ grass-dev mailing list grass-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Python and delayed or missing stderr output
On Wed, Sep 5, 2018 at 10:43 AM Markus Neteler wrote: > > Hi, > > AFAIK Python buffers (i.e. effectively delays) stderr output which is > unhelpful in the GRASS GIS context. > > Searching for a solution, I found this reference: sys.stdout.flush() > e.g. > https://stackoverflow.com/questions/10019456/usage-of-sys-stdout-flush-method That should be sys.stderr.flush() right? Regarding python's multiprocessing, it makes sense that stderr is suppressed because you would not know which process process produced which stderr (or stdout) message. There must be a method in python to redirect stderr and stdout for each process to a unique file, otherwise it would not be possible to find out why some process failed. Such a method would need to be implemented in each module usings python's multiprocessing. Markus M ___ grass-dev mailing list grass-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-dev
Re: [GRASS-dev] Python and delayed or missing stderr output
* Markus Neteler [2018-09-05 10:43:23 +0200]: Hi, AFAIK Python buffers (i.e. effectively delays) stderr output which is unhelpful in the GRASS GIS context. Searching for a solution, I found this reference: sys.stdout.flush() e.g. https://stackoverflow.com/questions/10019456/usage-of-sys-stdout-flush-method Would it be possible to add that to the GRASS GIS Python API? And would this then make Python scripts, by default, to issue any print statements (for debugging purposes or else) immediately? I am unsure, but I think I see exactly this "problem" sometimes, when scripting. The order of what is requested to print out is sometimes mixed. Thanks Markus. signature.asc Description: PGP signature ___ grass-dev mailing list grass-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-dev
[GRASS-dev] Python and delayed or missing stderr output
Hi, AFAIK Python buffers (i.e. effectively delays) stderr output which is unhelpful in the GRASS GIS context. Searching for a solution, I found this reference: sys.stdout.flush() e.g. https://stackoverflow.com/questions/10019456/usage-of-sys-stdout-flush-method Would it be possible to add that to the GRASS GIS Python API? thanks, markusN ___ grass-dev mailing list grass-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/grass-dev
