-------- Original-Nachricht --------
> Datum: Tue, 17 May 2011 13:11:41 +0100
> Von: Glynn Clements <gl...@gclements.plus.com>
> An: "Johannes Radinger" <jradin...@gmx.at>
> CC: grass-user@lists.osgeo.org
> Betreff: Re: [GRASS-user] Re: Using temp files in Grass Script
>
> Johannes Radinger wrote:
>
> > I found that thread about temporary maps...
> >
> > e.g in my case in my python script i use:
> >
> > #Convert river from vector to raster format
> > grass.run_command("v.to.rast",
> > input = "river_gen",
> > overwrite = True,
> > output = "river_raster",
> > use = "val",
> > value = res)
> >
> > #Thinning the rastarized river
> > grass.run_command("r.thin",
> > input = "river_raster",
> > overwrite = True,
> > output = "river_raster_thin")
> >
> > and here is the map river_raster only temporary for the thinning
> > process and the river_raster_thin is used for further calculations.
> > At the moment I have a g.remove to remove the river raster after
> > the thinning process but should I handle that with temporary files/maps
> > and if yes how is that exactly done in my python script?
>
> 1. In general, you should make an attempt at ensuring that temporary
> map names won't conflict with any existing map name. The usual
> approach is to include both ".tmp" and the PID in the map name, e.g.:
>
> import os
> ...
> global tmpmap
> tmp_map = 'river_raster.tmp.%d' % os.getpid()
>
> 2. Deletion should ideally be handled using an exit handler, e.g.:
>
> import os
> import atexit
> import grass.script as grass
>
> tmp_map = None
>
> def cleanup():
> if tmp_map:
> grass.run_command('g.remove', rast = tmp_map, quiet = True)
>
> def main():
> global tmpmap
> tmp_map = 'river_raster.tmp.%d' % os.getpid()
> ...
>
> if __name__ == "__main__":
> options, flags = grass.parser()
> atexit.register(cleanup)
> main()
>
> Using an exit handler ensures that the temporary map gets removed
> regardless of how the script terminates (e.g. if it terminates due to
> an exception).
Thank you for your nice examples how to do that with tmp files and the exit
handler.
Just some questions:
1) is the PID also used on windows systems? so can it be integrated in a script
which also windows users want to use? Is it correct that the PID is the same
value for running the whole script one time?
2) what exactly does the "global tmpmap"?
3)I've got a lot of tmp-files which will be created during the process, so is
there and option to tell the g.remove that all maps containing .tmp.%d' %
os.getpid() in the end should be removed instead of typing all the tmp map
files into the list of g.remove.
4) so the whole thing works that in the end all the tmp maps are deleted after
the processing of the script and after an exception etc.
/johannes
>
> --
> Glynn Clements <gl...@gclements.plus.com>
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