Get Number of CPUs for Any System, if Python is about

ncpus.py

# Based on : https://groups.google.com/d/msg/sage-devel/1lIJ961gV_w/y-2uqPCyzUMJ
import os
def ncpus():
    #for Linux, Unix and MacOS
    if hasattr(os, "sysconf"):
        if "SC_NPROCESSORS_ONLN" in os.sysconf_names:
            #Linux and Unix
            ncpus = os.sysconf("SC_NPROCESSORS_ONLN")
            if isinstance(ncpus, int) and ncpus > 0:
                return ncpus
        else:
            #MacOS X
            return int(os.popen2("sysctl -n hw.ncpu")[1].read())
    #for Windows
    if "NUMBER_OF_PROCESSORS" in os.environ:
        ncpus = int(os.environ["NUMBER_OF_PROCESSORS"])
        if ncpus > 0:
            return ncpus
    #return the default value
    return 1

print("CPUs: %d" % ncpus())

Thanks for this useful post. I should mention though the code is broken in Python3 since has_key attribute is removed from dict objects.

Replacing that line with if "SC_NPROCESSORS_ONLN" in os.sysconf_names: fixes it.

I've made the suggested changes. I'm glad you found the script useful!