1 def cpu_count():
 2     '''
 3     Returns the number of CPUs in the system
 4     '''
 5     if sys.platform == 'win32':
 6         try:
 7             num = int(os.environ['NUMBER_OF_PROCESSORS'])
 8         except (ValueError, KeyError):
 9             num = 0
10     elif 'bsd' in sys.platform or sys.platform == 'darwin':
11         comm = '/sbin/sysctl -n hw.ncpu'
12         if sys.platform == 'darwin':
13             comm = '/usr' + comm
14         try:
15             with os.popen(comm) as p:
16                 num = int(p.read())
17         except ValueError:
18             num = 0
19     else:
20         try:
21             num = os.sysconf('SC_NPROCESSORS_ONLN')
22         except (ValueError, OSError, AttributeError):
23             num = 0
24 
25     if num >= 1:
26         return num
27     else:
28         raise NotImplementedError('cannot determine number of cpus')

 1 /*[clinic input]
 2 os.cpu_count
 3 
 4 Return the number of CPUs in the system; return None if indeterminable.
 5 [clinic start generated code]*/
 6 
 7 static PyObject *
 8 os_cpu_count_impl(PyModuleDef *module)
 9 /*[clinic end generated code: output=c59ee7f6bce832b8 input=d55e2f8f3823a628]*/
10 {
11     int ncpu = 0;
12 #ifdef MS_WINDOWS
13     SYSTEM_INFO sysinfo;
14     GetSystemInfo(&sysinfo);
15     ncpu = sysinfo.dwNumberOfProcessors;
16 #elif defined(__hpux)
17     ncpu = mpctl(MPC_GETNUMSPUS, NULL, NULL);
18 #elif defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
19     ncpu = sysconf(_SC_NPROCESSORS_ONLN);
20 #elif defined(__DragonFly__) || \
21       defined(__OpenBSD__)   || \
22       defined(__FreeBSD__)   || \
23       defined(__NetBSD__)    || \
24       defined(__APPLE__)
25     int mib[2];
26     size_t len = sizeof(ncpu);
27     mib[0] = CTL_HW;
28     mib[1] = HW_NCPU;
29     if (sysctl(mib, 2, &ncpu, &len, NULL, 0) != 0)
30         ncpu = 0;
31 #endif
32     if (ncpu >= 1)
33         return PyLong_FromLong(ncpu);
34     else
35         Py_RETURN_NONE;
36 }