From fe612489c044a0e076ac227af60b56fa4c1963e9 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Fri, 6 Jan 2023 14:05:40 +0300
Subject: [PATCH 1/2] gh-100792: Make `email.message.Message.__contains__`
 twice as fast

---
 Lib/email/message.py                                        | 6 +++++-
 .../Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst  | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst

diff --git a/Lib/email/message.py b/Lib/email/message.py
index 65fda507251ce3..b540c33984a753 100644
--- a/Lib/email/message.py
+++ b/Lib/email/message.py
@@ -448,7 +448,11 @@ def __delitem__(self, name):
         self._headers = newheaders
 
     def __contains__(self, name):
-        return name.lower() in [k.lower() for k, v in self._headers]
+        name_lower = name.lower()
+        for k, v in self._headers:
+            if name_lower == k.lower():
+                return True
+        return False
 
     def __iter__(self):
         for field, value in self._headers:
diff --git a/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst b/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst
new file mode 100644
index 00000000000000..fc73c973dbe1ee
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst
@@ -0,0 +1 @@
+Make ``email.message.Message.__contains__`` twice as fast.

From d2d0c76d6061fd270c514b4a6402788c2d3ab9ec Mon Sep 17 00:00:00 2001
From: Nikita Sobolev <mail@sobolevn.me>
Date: Sat, 7 Jan 2023 20:22:05 +0300
Subject: [PATCH 2/2] Update
 Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
---
 .../next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst b/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst
index fc73c973dbe1ee..5966bc1e605158 100644
--- a/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst
+++ b/Misc/NEWS.d/next/Library/2023-01-06-14-05-15.gh-issue-100792.CEOJth.rst
@@ -1 +1 @@
-Make ``email.message.Message.__contains__`` twice as fast.
+Make :meth:`email.message.Message.__contains__` twice as fast.