Cross platform way of finding number of processors on a machine?

Nick Craig-Wood nick at craig-wood.com
Sat Oct 6 20:30:13 CEST 2007


Lawrence Oluyede <raims at dot.com> wrote:
>  John <weekender_ny at yahoo.com> wrote:
> > Is there a way to find the number of processors on a machine (on linux/
> > windows/macos/cygwin) using python code (using the same code/cross
> > platform code)?
> 
>  From processing <http://cheeseshop.python.org/pypi/processing/0.34> :
> 
>  def cpuCount():
>      '''
>      Returns the number of CPUs in the system
>      '''
>      if sys.platform == 'win32':
>          try:
>              num = int(os.environ['NUMBER_OF_PROCESSORS'])
>          except (ValueError, KeyError):
>              pass
>      elif sys.platform == 'darwin':
>          try:
>              num = int(os.popen('sysctl -n hw.ncpu').read())
>          except ValueError:
>              pass
>      else:
>          try:
>              num = os.sysconf('SC_NPROCESSORS_ONLN')
>          except (ValueError, OSError, AttributeError):
>              pass
>          
>      if num >= 1:
>          return num
>      else:
>          raise NotImplementedError


There is a bug in that code...

NotImplementedError will never be raised because num won't have been
set.  It will raise "UnboundLocalError: local variable 'num'
referenced before assignment" instead

-- 
Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick



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