diff -r 5673cf852daa Doc/library/os.rst
--- a/Doc/library/os.rst	Sat Oct 01 01:06:51 2016 -0500
+++ b/Doc/library/os.rst	Sat Oct 01 23:50:09 2016 +0530
@@ -3511,7 +3511,7 @@
    .. versionadded:: 3.3
 
 
-.. function:: waitpid(pid, options)
+.. function:: waitpid(pid, options=0)
 
    The details of this function differ on Unix and Windows.
 
diff -r 5673cf852daa Lib/distutils/spawn.py
--- a/Lib/distutils/spawn.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/distutils/spawn.py	Sat Oct 01 23:50:09 2016 +0530
@@ -135,7 +135,7 @@
         # (ie. keep waiting if it's merely stopped)
         while True:
             try:
-                pid, status = os.waitpid(pid, 0)
+                pid, status = os.waitpid(pid)
             except OSError as exc:
                 if not DEBUG:
                     cmd = executable
diff -r 5673cf852daa Lib/http/server.py
--- a/Lib/http/server.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/http/server.py	Sat Oct 01 23:50:09 2016 +0530
@@ -1107,7 +1107,7 @@
             pid = os.fork()
             if pid != 0:
                 # Parent
-                pid, sts = os.waitpid(pid, 0)
+                pid, sts = os.waitpid(pid)
                 # throw away additional data [see bug #427345]
                 while select.select([self.rfile], [], [], 0)[0]:
                     if not self.rfile.read(1):
diff -r 5673cf852daa Lib/os.py
--- a/Lib/os.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/os.py	Sat Oct 01 23:50:09 2016 +0530
@@ -911,7 +911,7 @@
             if mode == P_NOWAIT:
                 return pid # Caller is responsible for waiting!
             while 1:
-                wpid, sts = waitpid(pid, 0)
+                wpid, sts = waitpid(pid)
                 if WIFSTOPPED(sts):
                     continue
                 elif WIFSIGNALED(sts):
diff -r 5673cf852daa Lib/pty.py
--- a/Lib/pty.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/pty.py	Sat Oct 01 23:50:09 2016 +0530
@@ -167,4 +167,4 @@
             tty.tcsetattr(STDIN_FILENO, tty.TCSAFLUSH, mode)
 
     os.close(master_fd)
-    return os.waitpid(pid, 0)[1]
+    return os.waitpid(pid)[1]
diff -r 5673cf852daa Lib/socketserver.py
--- a/Lib/socketserver.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/socketserver.py	Sat Oct 01 23:50:09 2016 +0530
@@ -561,7 +561,7 @@
             # above max_children.
             while len(self.active_children) >= self.max_children:
                 try:
-                    pid, _ = os.waitpid(-1, 0)
+                    pid, _ = os.waitpid(-1)
                     self.active_children.discard(pid)
                 except ChildProcessError:
                     # we don't have any children, we're done
diff -r 5673cf852daa Lib/subprocess.py
--- a/Lib/subprocess.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/subprocess.py	Sat Oct 01 23:50:09 2016 +0530
@@ -295,7 +295,7 @@
 sts = os.system("mycmd" + " myarg")
 ==>
 p = Popen("mycmd" + " myarg", shell=True)
-pid, sts = os.waitpid(p.pid, 0)
+pid, sts = os.waitpid(p.pid)
 
 Note:
 
@@ -1545,7 +1545,7 @@
 
             if errpipe_data:
                 try:
-                    pid, sts = os.waitpid(self.pid, 0)
+                    pid, sts = os.waitpid(self.pid)
                     if pid == self.pid:
                         self._handle_exitstatus(sts)
                     else:
diff -r 5673cf852daa Lib/test/eintrdata/eintr_tester.py
--- a/Lib/test/eintrdata/eintr_tester.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/eintrdata/eintr_tester.py	Sat Oct 01 23:50:09 2016 +0530
@@ -101,7 +101,7 @@
         proc.wait()
 
     def test_waitpid(self):
-        self._test_wait_single(lambda pid: os.waitpid(pid, 0))
+        self._test_wait_single(lambda pid: os.waitpid(pid))
 
     @unittest.skipUnless(hasattr(os, 'wait4'), 'requires wait4()')
     def test_wait4(self):
diff -r 5673cf852daa Lib/test/test_mailbox.py
--- a/Lib/test/test_mailbox.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_mailbox.py	Sat Oct 01 23:50:09 2016 +0530
@@ -1066,7 +1066,7 @@
             # Signal the child it can now release the lock and exit.
             p.send(b'p')
             # Wait for child to exit.  Locking should now succeed.
-            exited_pid, status = os.waitpid(pid, 0)
+            exited_pid, status = os.waitpid(pid)
 
         self._box.lock()
         self._box.unlock()
diff -r 5673cf852daa Lib/test/test_os.py
--- a/Lib/test/test_os.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_os.py	Sat Oct 01 23:50:09 2016 +0530
@@ -2183,7 +2183,7 @@
         args = [sys.executable, '-c', 'pass']
         # Add an implicit test for PyUnicode_FSConverter().
         pid = os.spawnv(os.P_NOWAIT, _PathLike(args[0]), args)
-        status = os.waitpid(pid, 0)
+        status = os.waitpid(pid)
         self.assertEqual(status, (pid, 0))
 
 
@@ -2268,7 +2268,7 @@
     def test_nowait(self):
         args = self.create_args()
         pid = os.spawnv(os.P_NOWAIT, args[0], args)
-        result = os.waitpid(pid, 0)
+        result = os.waitpid(pid)
         self.assertEqual(result[0], pid)
         status = result[1]
         if hasattr(os, 'WIFEXITED'):
diff -r 5673cf852daa Lib/test/test_platform.py
--- a/Lib/test/test_platform.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_platform.py	Sat Oct 01 23:50:09 2016 +0530
@@ -255,7 +255,7 @@
 
         else:
             # parent
-            cpid, sts = os.waitpid(pid, 0)
+            cpid, sts = os.waitpid(pid)
             self.assertEqual(cpid, pid)
             self.assertEqual(sts, 0)
 
diff -r 5673cf852daa Lib/test/test_posix.py
--- a/Lib/test/test_posix.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_posix.py	Sat Oct 01 23:50:09 2016 +0530
@@ -171,7 +171,7 @@
                 os.chdir(os.path.split(sys.executable)[0])
                 posix.execve(fp, [sys.executable, '-c', 'pass'], os.environ)
             else:
-                self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+                self.assertEqual(os.waitpid(pid), (pid))
         finally:
             os.close(fp)
 
diff -r 5673cf852daa Lib/test/test_pty.py
--- a/Lib/test/test_pty.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_pty.py	Sat Oct 01 23:50:09 2016 +0530
@@ -173,7 +173,7 @@
             ##             'Good: OSError was raised.', '']:
             ##    raise TestFailed("Unexpected output from child: %r" % line)
 
-            (pid, status) = os.waitpid(pid, 0)
+            (pid, status) = os.waitpid(pid)
             res = status >> 8
             debug("Child (%d) exited with status %d (%d)." % (pid, res, status))
             if res == 1:
diff -r 5673cf852daa Lib/test/test_socketserver.py
--- a/Lib/test/test_socketserver.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_socketserver.py	Sat Oct 01 23:50:09 2016 +0530
@@ -63,7 +63,7 @@
         # Don't raise an exception; it would be caught by the test harness.
         os._exit(72)
     yield None
-    pid2, status = os.waitpid(pid, 0)
+    pid2, status = os.waitpid(pid)
     testcase.assertEqual(pid2, pid)
     testcase.assertEqual(72 << 8, status)
 
@@ -373,7 +373,7 @@
     class ForkingErrorTestServer(socketserver.ForkingMixIn, BaseErrorTestServer):
         def wait_done(self):
             [child] = self.active_children
-            os.waitpid(child, 0)
+            os.waitpid(child)
             self.active_children.clear()
 
 
diff -r 5673cf852daa Lib/test/test_ssl.py
--- a/Lib/test/test_ssl.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_ssl.py	Sat Oct 01 23:50:09 2016 +0530
@@ -230,7 +230,7 @@
         else:
             os.close(wfd)
             self.addCleanup(os.close, rfd)
-            _, status = os.waitpid(pid, 0)
+            _, status = os.waitpid(pid)
             self.assertEqual(status, 0)
 
             child_random = os.read(rfd, 16)
diff -r 5673cf852daa Lib/test/test_subprocess.py
--- a/Lib/test/test_subprocess.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_subprocess.py	Sat Oct 01 23:50:09 2016 +0530
@@ -2359,7 +2359,7 @@
                                   stderr=subprocess.PIPE) as proc:
                 pass
         # p should have been wait()ed on, and removed from the _active list
-        self.assertRaises(OSError, os.waitpid, pid, 0)
+        self.assertRaises(OSError, os.waitpid, pid)
         self.assertNotIn(ident, [id(o) for o in subprocess._active])
 
     def test_close_fds_after_preexec(self):
diff -r 5673cf852daa Lib/test/test_threading.py
--- a/Lib/test/test_threading.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_threading.py	Sat Oct 01 23:50:09 2016 +0530
@@ -472,7 +472,7 @@
             if pid == 0:
                 os._exit(1 if t.is_alive() else 0)
             else:
-                pid, status = os.waitpid(pid, 0)
+                pid, status = os.waitpid(pid)
                 self.assertEqual(0, status)
 
     def test_main_thread(self):
@@ -501,7 +501,7 @@
                 print(main.ident == threading.current_thread().ident)
                 print(main.ident == threading.get_ident())
             else:
-                os.waitpid(pid, 0)
+                os.waitpid(pid)
         """
         _, out, err = assert_python_ok("-c", code)
         data = out.decode().replace('\r', '')
@@ -526,7 +526,7 @@
                     # we have to flush before exit.
                     sys.stdout.flush()
                 else:
-                    os.waitpid(pid, 0)
+                    os.waitpid(pid)
 
             th = threading.Thread(target=f)
             th.start()
@@ -694,7 +694,7 @@
         script = """if 1:
             childpid = os.fork()
             if childpid != 0:
-                os.waitpid(childpid, 0)
+                os.waitpid(childpid)
                 sys.exit(0)
 
             t = threading.Thread(target=joiningfunc,
@@ -715,7 +715,7 @@
             def worker():
                 childpid = os.fork()
                 if childpid != 0:
-                    os.waitpid(childpid, 0)
+                    os.waitpid(childpid)
                     sys.exit(0)
 
                 t = threading.Thread(target=joiningfunc,
@@ -782,7 +782,7 @@
             # just fork a child process and wait it
             pid = os.fork()
             if pid > 0:
-                os.waitpid(pid, 0)
+                os.waitpid(pid)
             else:
                 os._exit(0)
 
@@ -815,7 +815,7 @@
             else:
                 os._exit(1)
         else:
-            _, status = os.waitpid(pid, 0)
+            _, status = os.waitpid(pid)
             self.assertEqual(0, status)
 
         for t in threads:
diff -r 5673cf852daa Lib/test/test_tracemalloc.py
--- a/Lib/test/test_tracemalloc.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_tracemalloc.py	Sat Oct 01 23:50:09 2016 +0530
@@ -290,7 +290,7 @@
             finally:
                 os._exit(exitcode)
         else:
-            pid2, status = os.waitpid(pid, 0)
+            pid2, status = os.waitpid(pid)
             self.assertTrue(os.WIFEXITED(status))
             exitcode = os.WEXITSTATUS(status)
             self.assertEqual(exitcode, 0)
diff -r 5673cf852daa Lib/test/test_uuid.py
--- a/Lib/test/test_uuid.py	Sat Oct 01 01:06:51 2016 -0500
+++ b/Lib/test/test_uuid.py	Sat Oct 01 23:50:09 2016 +0530
@@ -403,7 +403,7 @@
             os.close(fds[1])
             self.addCleanup(os.close, fds[0])
             parent_value = uuid.uuid4().hex
-            os.waitpid(pid, 0)
+            os.waitpid(pid)
             child_value = os.read(fds[0], 100).decode('latin-1')
 
             self.assertNotEqual(parent_value, child_value)
diff -r 5673cf852daa Modules/clinic/posixmodule.c.h
--- a/Modules/clinic/posixmodule.c.h	Sat Oct 01 01:06:51 2016 -0500
+++ b/Modules/clinic/posixmodule.c.h	Sat Oct 01 23:50:09 2016 +0530
@@ -2963,7 +2963,7 @@
 #if defined(HAVE_WAITPID)
 
 PyDoc_STRVAR(os_waitpid__doc__,
-"waitpid($module, pid, options, /)\n"
+"waitpid($module, /, pid, options=0)\n"
 "--\n"
 "\n"
 "Wait for completion of a given child process.\n"
@@ -2974,19 +2974,21 @@
 "The options argument is ignored on Windows.");
 
 #define OS_WAITPID_METHODDEF    \
-    {"waitpid", (PyCFunction)os_waitpid, METH_VARARGS, os_waitpid__doc__},
+    {"waitpid", (PyCFunction)os_waitpid, METH_FASTCALL, os_waitpid__doc__},
 
 static PyObject *
 os_waitpid_impl(PyObject *module, pid_t pid, int options);
 
 static PyObject *
-os_waitpid(PyObject *module, PyObject *args)
+os_waitpid(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"pid", "options", NULL};
+    static _PyArg_Parser _parser = {"" _Py_PARSE_PID "|i:waitpid", _keywords, 0};
     pid_t pid;
-    int options;
-
-    if (!PyArg_ParseTuple(args, "" _Py_PARSE_PID "i:waitpid",
+    int options = 0;
+
+    if (!_PyArg_ParseStack(args, nargs, kwnames, &_parser,
         &pid, &options)) {
         goto exit;
     }
@@ -3001,7 +3003,7 @@
 #if defined(HAVE_CWAIT)
 
 PyDoc_STRVAR(os_waitpid__doc__,
-"waitpid($module, pid, options, /)\n"
+"waitpid($module, /, pid, options=0)\n"
 "--\n"
 "\n"
 "Wait for completion of a given process.\n"
@@ -3012,19 +3014,21 @@
 "The options argument is ignored on Windows.");
 
 #define OS_WAITPID_METHODDEF    \
-    {"waitpid", (PyCFunction)os_waitpid, METH_VARARGS, os_waitpid__doc__},
+    {"waitpid", (PyCFunction)os_waitpid, METH_FASTCALL, os_waitpid__doc__},
 
 static PyObject *
 os_waitpid_impl(PyObject *module, intptr_t pid, int options);
 
 static PyObject *
-os_waitpid(PyObject *module, PyObject *args)
+os_waitpid(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"pid", "options", NULL};
+    static _PyArg_Parser _parser = {"" _Py_PARSE_INTPTR "|i:waitpid", _keywords, 0};
     intptr_t pid;
-    int options;
-
-    if (!PyArg_ParseTuple(args, "" _Py_PARSE_INTPTR "i:waitpid",
+    int options = 0;
+
+    if (!_PyArg_ParseStack(args, nargs, kwnames, &_parser,
         &pid, &options)) {
         goto exit;
     }
@@ -6148,4 +6152,4 @@
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=b9ed5703d2feb0d9 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=271dd33f2c82eb95 input=a9049054013a1b77]*/
diff -r 5673cf852daa Modules/posixmodule.c
--- a/Modules/posixmodule.c	Sat Oct 01 01:06:51 2016 -0500
+++ b/Modules/posixmodule.c	Sat Oct 01 23:50:09 2016 +0530
@@ -6825,8 +6825,7 @@
 /*[clinic input]
 os.waitpid
     pid: pid_t
-    options: int
-    /
+    options: int = 0
 
 Wait for completion of a given child process.
 
@@ -6838,7 +6837,7 @@
 
 static PyObject *
 os_waitpid_impl(PyObject *module, pid_t pid, int options)
-/*[clinic end generated code: output=5c37c06887a20270 input=0bf1666b8758fda3]*/
+/*[clinic end generated code: output=5c37c06887a20270 input=dea600de625eec93]*/
 {
     pid_t res;
     int async_err = 0;
@@ -6860,8 +6859,7 @@
 /*[clinic input]
 os.waitpid
     pid: intptr_t
-    options: int
-    /
+    options: int = 0
 
 Wait for completion of a given process.
 
@@ -6873,7 +6871,7 @@
 
 static PyObject *
 os_waitpid_impl(PyObject *module, intptr_t pid, int options)
-/*[clinic end generated code: output=be836b221271d538 input=40f2440c515410f8]*/
+/*[clinic end generated code: output=be836b221271d538 input=ae2f154feb382cba]*/
 {
     int status;
     intptr_t res;