fix #1437: return pids() in sorted order

5 files changed, 14 insertions, 11 deletions

diff --git a/HISTORY.rst b/HISTORY.rst
index c553086b..9fcc72f8 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -18,6 +18,7 @@ XXXX-XX-XX
 - 1426_: [Windows] PAGESIZE and number of processors is now calculated on
   startup.
 - 1433_: new Process.parents() method.  (idea by Ghislain Le Meur)
+- 1437_: pids() are returned in sorted order.
 
 **Bug fixes**
 
diff --git a/docs/index.rst b/docs/index.rst
index 8983e880..a6f2ba73 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -817,13 +817,17 @@ Functions
 
 .. function:: pids()
 
-  Return a list of current running PIDs. To iterate over all processes
-  and avoid race conditions :func:`process_iter()` should be preferred.
+  Return a sorted list of current running PIDs.
+  To iterate over all processes and avoid race conditions :func:`process_iter()`
+  should be preferred.
 
   >>> import psutil
   >>> psutil.pids()
   [1, 2, 3, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, ..., 32498]
 
+  .. versionchanged::
+    5.6.0 PIDs are returned in sorted order
+
 .. function:: process_iter(attrs=None, ad_value=None)
 
   Return an iterator yielding a :class:`Process` class instance for all running
diff --git a/psutil/__init__.py b/psutil/__init__.py
index b5a584f2..1893298b 100644
--- a/psutil/__init__.py
+++ b/psutil/__init__.py
@@ -399,7 +399,7 @@ def _pprint_secs(secs):
 
 @lru_cache()
 def _first_pid():
-    return sorted(pids())[0]
+    return pids()[0]
 
 
 # =====================================================================
@@ -1500,7 +1500,7 @@ _as_dict_attrnames = set(
 
 def pids():
     """Return a list of current running PIDs."""
-    return _psplatform.pids()
+    return sorted(_psplatform.pids())
 
 
 def pid_exists(pid):
diff --git a/psutil/tests/test_posix.py b/psutil/tests/test_posix.py
index 955a4834..15d2f127 100755
--- a/psutil/tests/test_posix.py
+++ b/psutil/tests/test_posix.py
@@ -321,10 +321,8 @@ class TestSystemAPIs(unittest.TestCase):
     def test_pids(self):
         # Note: this test might fail if the OS is starting/killing
         # other processes in the meantime
-        pids_ps = ps("pid")
+        pids_ps = sorted(ps("pid"))
         pids_psutil = psutil.pids()
-        pids_ps.sort()
-        pids_psutil.sort()
 
         # on MACOS and OPENBSD ps doesn't show pid 0
         if MACOS or OPENBSD and 0 not in pids_ps:
diff --git a/psutil/tests/test_system.py b/psutil/tests/test_system.py
index b0b7e4f0..1236af3b 100755
--- a/psutil/tests/test_system.py
+++ b/psutil/tests/test_system.py
@@ -242,11 +242,11 @@ class TestSystemAPIs(unittest.TestCase):
             self.assertFalse(psutil.pid_exists(pid), msg=pid)
 
     def test_pids(self):
-        plist = [x.pid for x in psutil.process_iter()]
-        pidlist = psutil.pids()
-        self.assertEqual(plist.sort(), pidlist.sort())
+        pidslist = psutil.pids()
+        procslist = [x.pid for x in psutil.process_iter()]
         # make sure every pid is unique
-        self.assertEqual(len(pidlist), len(set(pidlist)))
+        self.assertEqual(sorted(set(pidslist)), pidslist)
+        self.assertEqual(pidslist, procslist)
 
     def test_test(self):
         # test for psutil.test() function