Issue #17914: Add os.cpu_count(). Patch by Yogesh Chaudhari, based on an

initial patch by Trent Nelson.

2 files changed, 13 insertions, 22 deletions

diff --git a/Lib/multiprocessing/__init__.py b/Lib/multiprocessing/__init__.py
index b5f16d7..b42613f 100644
--- a/Lib/multiprocessing/__init__.py
+++ b/Lib/multiprocessing/__init__.py
@@ -85,30 +85,11 @@ def cpu_count():
     '''
     Returns the number of CPUs in the system
     '''
-    if sys.platform == 'win32':
-        try:
-            num = int(os.environ['NUMBER_OF_PROCESSORS'])
-        except (ValueError, KeyError):
-            num = 0
-    elif 'bsd' in sys.platform or sys.platform == 'darwin':
-        comm = '/sbin/sysctl -n hw.ncpu'
-        if sys.platform == 'darwin':
-            comm = '/usr' + comm
-        try:
-            with os.popen(comm) as p:
-                num = int(p.read())
-        except ValueError:
-            num = 0
+    num = os.cpu_count()
+    if num is None:
+        raise NotImplementedError('cannot determine number of cpus')
     else:
-        try:
-            num = os.sysconf('SC_NPROCESSORS_ONLN')
-        except (ValueError, OSError, AttributeError):
-            num = 0
-
-    if num >= 1:
         return num
-    else:
-        raise NotImplementedError('cannot determine number of cpus')
 
 def freeze_support():
     '''
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 3a38285..65d3c3b 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2216,6 +2216,15 @@ class OSErrorTests(unittest.TestCase):
                 else:
                     self.fail("No exception thrown by {}".format(func))
 
+class CPUCountTests(unittest.TestCase):
+    def test_cpu_count(self):
+        cpus = os.cpu_count()
+        if cpus is not None:
+            self.assertIsInstance(cpus, int)
+            self.assertGreater(cpus, 0)
+        else:
+            self.skipTest("Could not determine the number of CPUs")
+
 @support.reap_threads
 def test_main():
     support.run_unittest(
@@ -2246,6 +2255,7 @@ def test_main():
         TermsizeTests,
         OSErrorTests,
         RemoveDirsTests,
+        CPUCountTests,
     )
 
 if __name__ == "__main__":