[GRASS-dev] [GRASS GIS] #2608: Launching Python script on Windows fails with missing freeze_support

[GRASS GIS]

#2608: Launching Python script on Windows fails with missing freeze_support
-------------------------+--------------------------------------------------
 Reporter:  marisn       |       Owner:  grass-dev@…              
     Type:  defect       |      Status:  new                      
 Priority:  normal       |   Milestone:                           
Component:  Python       |     Version:  7.0.0                    
 Keywords:               |    Platform:  MSWindows Vista          
      Cpu:  Unspecified  |  
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 Launch the following script on Windows:
 {{{
 from grass.pygrass.modules.shortcuts import raster as r
 r.mapcalc("rand0 = round(rand(0,1))", s=True)
 r.neighbors(input="rand0", output="count", method="count")
 r.mapcalc("rand1 = if (count > 3, 1, null())")
 r.mapcalc("rand2 = if (count < 1, 1, null())")
 }}}
 and observe an error:
 {{{
 C:\Users\tests\Documents\rand.py
 Traceback (most recent call last):
   File "<string>", line 1, in <module>
   File "C:\Program Files\GRASS GIS
 7.0.0\Python27\lib\multiprocessing\forking.py", line 380, in
 main
     prepare(preparation_data)
   File "C:\Program Files\GRASS GIS
 7.0.0\Python27\lib\multiprocessing\forking.py", line 495, in
 prepare
     '__parents_main__', file, path_name, etc
   File "C:\Users\tests\Documents\rand.py", line 2, in
 <module>
     r.mapcalc("rand0 = round(rand(0,1))", s=True)
   File "C:\Program Files\GRASS GIS
 7.0.0\etc\python\grass\pygrass\modules\interface\module.py",
 line 616, in __call__
     return self.run()
   File "C:\Program Files\GRASS GIS
 7.0.0\etc\python\grass\pygrass\modules\interface\module.py",
 line 714, in run
     get_msgr().debug(1, self.get_bash())
   File "C:\Program Files\GRASS GIS
 7.0.0\etc\python\grass\pygrass\messages\__init__.py", line
 352, in get_msgr
     _instance[0] = Messenger(*args, **kwargs)
   File "C:\Program Files\GRASS GIS
 7.0.0\etc\python\grass\pygrass\messages\__init__.py", line
 175, in __init__
     self.start_server()
   File "C:\Program Files\GRASS GIS
 7.0.0\etc\python\grass\pygrass\messages\__init__.py", line
 185, in start_server
     self.server.start()
   File "C:\Program Files\GRASS GIS
 7.0.0\Python27\lib\multiprocessing\process.py", line 130, in
 start
     self._popen = Popen(self)
   File "C:\Program Files\GRASS GIS
 7.0.0\Python27\lib\multiprocessing\forking.py", line 258, in
 __init__
     cmd = get_command_line() + [rhandle]
   File "C:\Program Files\GRASS GIS
 7.0.0\Python27\lib\multiprocessing\forking.py", line 358, in
 get_command_line
     is not going to be frozen to produce a Windows executable.''')
 RuntimeError:
             Attempt to start a new process before the current process
             has finished its bootstrapping phase.
             This probably means that you are on Windows and you have
             forgotten to use the proper idiom in the main module:
                 if __name__ == '__main__':
                     freeze_support()
                     ...
             The "freeze_support()" line can be omitted if the program
             is not going to be frozen to produce a Windows executable.
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/2608>
GRASS GIS <http://grass.osgeo.org>