From 8edbde4860e40aff2713e2ec2bd2e578e588b6d0 Mon Sep 17 00:00:00 2001
From: Dong-hee Na <donghee.na@python.org>
Date: Wed, 19 Jul 2023 10:43:03 +0900
Subject: [PATCH 1/2] gh-106751: Optimize SelectSelector.select() for many
 iteration case

---
 Lib/selectors.py                                   | 14 ++++++--------
 .../2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst |  2 ++
 2 files changed, 8 insertions(+), 8 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst

diff --git a/Lib/selectors.py b/Lib/selectors.py
index d13405963f219d..a98dc431d584df 100644
--- a/Lib/selectors.py
+++ b/Lib/selectors.py
@@ -316,15 +316,13 @@ def select(self, timeout=None):
             return ready
         r = set(r)
         w = set(w)
-        for fd in r | w:
-            events = 0
-            if fd in r:
-                events |= EVENT_READ
-            if fd in w:
-                events |= EVENT_WRITE
-
-            key = self._fd_to_key.get(fd)
+        rw = r | w
+        fd_to_key_get = self._fd_to_key.get
+        for fd in rw:
+            key = fd_to_key_get(fd)
             if key:
+                events = ((fd in r and EVENT_READ)
+                          | (fd in w and EVENT_WRITE))
                 ready.append((key, events & key.events))
         return ready
 
diff --git a/Misc/NEWS.d/next/Library/2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst b/Misc/NEWS.d/next/Library/2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst
new file mode 100644
index 00000000000000..2696b560371d13
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-07-19-10-45-24.gh-issue-106751.3HJ1of.rst
@@ -0,0 +1,2 @@
+Optimize :meth:`SelectSelector.select` for many iteration case. Patch By
+Dong-hee Na.

From fdab58bb5ea6f1bc0b6dce5d6054c3a632a60c36 Mon Sep 17 00:00:00 2001
From: Dong-hee Na <donghee.na@python.org>
Date: Wed, 19 Jul 2023 10:49:35 +0900
Subject: [PATCH 2/2] Use frozenset

---
 Lib/selectors.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Lib/selectors.py b/Lib/selectors.py
index a98dc431d584df..13497a24097232 100644
--- a/Lib/selectors.py
+++ b/Lib/selectors.py
@@ -314,8 +314,8 @@ def select(self, timeout=None):
             r, w, _ = self._select(self._readers, self._writers, [], timeout)
         except InterruptedError:
             return ready
-        r = set(r)
-        w = set(w)
+        r = frozenset(r)
+        w = frozenset(w)
         rw = r | w
         fd_to_key_get = self._fd_to_key.get
         for fd in rw: