From: Andrew Svetlov <andrew.svetlov@gmail.com>
Date: Wed, 26 Dec 2018 18:45:33 +0000 (+0200)
Subject: Speed-up building enums by value, e.g. http.HTTPStatus(200) (#11318)
X-Git-Tag: v3.8.0a1~193
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=34ae04f74dcf4ac97d07c3e82eaf8f619d80cedb;p=thirdparty%2FPython%2Fcpython.git

Speed-up building enums by value, e.g. http.HTTPStatus(200) (#11318)

bpo-35585: Speed up enum by-value lookup
---

diff --git a/Lib/enum.py b/Lib/enum.py
index fec1aed9b25c..f7452f0cc0aa 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -563,8 +563,10 @@ class Enum(metaclass=EnumMeta):
         # by-value search for a matching enum member
         # see if it's in the reverse mapping (for hashable values)
         try:
-            if value in cls._value2member_map_:
-                return cls._value2member_map_[value]
+            return cls._value2member_map_[value]
+        except KeyError:
+            # Not found, no need to do long O(n) search
+            pass
         except TypeError:
             # not there, now do long search -- O(n) behavior
             for member in cls._member_map_.values():
diff --git a/Misc/NEWS.d/next/Library/2018-12-26-02-28-00.bpo-35585.Lkzd3Z.rst b/Misc/NEWS.d/next/Library/2018-12-26-02-28-00.bpo-35585.Lkzd3Z.rst
new file mode 100644
index 000000000000..247a4ae6800f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-12-26-02-28-00.bpo-35585.Lkzd3Z.rst
@@ -0,0 +1 @@
+Speed-up building enums by value, e.g. http.HTTPStatus(200).