From 832c37d42a395d4ea45994daffa5e41bd74ac1bb Mon Sep 17 00:00:00 2001
From: Pieter Eendebak <pieter.eendebak@gmail.com>
Date: Thu, 20 Jul 2023 02:53:11 +0200
Subject: [PATCH] gh-106751: Optimize _PolllikeSelector for many iteration case
 (gh-106884)

---
 Lib/selectors.py                              | 26 +++++++------------
 ...-07-19-09-11-08.gh-issue-106751.U9nD_B.rst |  1 +
 2 files changed, 10 insertions(+), 17 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-07-19-09-11-08.gh-issue-106751.U9nD_B.rst

diff --git a/Lib/selectors.py b/Lib/selectors.py
index 13497a24097232..20367c9152f331 100644
--- a/Lib/selectors.py
+++ b/Lib/selectors.py
@@ -339,11 +339,8 @@ def __init__(self):
 
     def register(self, fileobj, events, data=None):
         key = super().register(fileobj, events, data)
-        poller_events = 0
-        if events & EVENT_READ:
-            poller_events |= self._EVENT_READ
-        if events & EVENT_WRITE:
-            poller_events |= self._EVENT_WRITE
+        poller_events = ((events & EVENT_READ and self._EVENT_READ)
+                         | (events & EVENT_WRITE and self._EVENT_WRITE) )
         try:
             self._selector.register(key.fd, poller_events)
         except:
@@ -369,11 +366,8 @@ def modify(self, fileobj, events, data=None):
 
         changed = False
         if events != key.events:
-            selector_events = 0
-            if events & EVENT_READ:
-                selector_events |= self._EVENT_READ
-            if events & EVENT_WRITE:
-                selector_events |= self._EVENT_WRITE
+            selector_events = ((events & EVENT_READ and self._EVENT_READ)
+                               | (events & EVENT_WRITE and self._EVENT_WRITE))
             try:
                 self._selector.modify(key.fd, selector_events)
             except:
@@ -404,15 +398,13 @@ def select(self, timeout=None):
             fd_event_list = self._selector.poll(timeout)
         except InterruptedError:
             return ready
-        for fd, event in fd_event_list:
-            events = 0
-            if event & ~self._EVENT_READ:
-                events |= EVENT_WRITE
-            if event & ~self._EVENT_WRITE:
-                events |= EVENT_READ
 
-            key = self._fd_to_key.get(fd)
+        fd_to_key_get = self._fd_to_key.get
+        for fd, event in fd_event_list:
+            key = fd_to_key_get(fd)
             if key:
+                events = ((event & ~self._EVENT_READ and EVENT_WRITE)
+                           | (event & ~self._EVENT_WRITE and EVENT_READ))
                 ready.append((key, events & key.events))
         return ready
 
diff --git a/Misc/NEWS.d/next/Library/2023-07-19-09-11-08.gh-issue-106751.U9nD_B.rst b/Misc/NEWS.d/next/Library/2023-07-19-09-11-08.gh-issue-106751.U9nD_B.rst
new file mode 100644
index 00000000000000..b9a9b563ad2267
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-07-19-09-11-08.gh-issue-106751.U9nD_B.rst
@@ -0,0 +1 @@
+Optimize :meth:`_PollLikeSelector.select` for many iteration case.