From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Wed, 31 Jul 2019 20:22:09 +0000 (-0700)
Subject: bpo-37723: Fix performance regression on regular expression parsing. (GH-15030)
X-Git-Tag: v3.8.0b4~145
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=77fcccb5321137456549b7f55b819f2c8a4c78a4;p=thirdparty%2FPython%2Fcpython.git

bpo-37723: Fix performance regression on regular expression parsing. (GH-15030)


Improve performance of sre_parse._uniq function.
(cherry picked from commit 9f55551f3df238e58315e724e50cb0d574d75b94)

Co-authored-by: yannvgn <hi@yannvgn.io>
---

diff --git a/Lib/sre_parse.py b/Lib/sre_parse.py
index 84c912573e7f..83119168e637 100644
--- a/Lib/sre_parse.py
+++ b/Lib/sre_parse.py
@@ -430,13 +430,7 @@ def _escape(source, escape, state):
     raise source.error("bad escape %s" % escape, len(escape))
 
 def _uniq(items):
-    if len(set(items)) == len(items):
-        return items
-    newitems = []
-    for item in items:
-        if item not in newitems:
-            newitems.append(item)
-    return newitems
+    return list(dict.fromkeys(items))
 
 def _parse_sub(source, state, verbose, nested):
     # parse an alternation: a|b|c
diff --git a/Misc/ACKS b/Misc/ACKS
index 829aa796c847..ad2e0a1996aa 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1702,6 +1702,7 @@ Michael Urman
 Hector Urtubia
 Lukas Vacek
 Ville Vainio
+Yann Vaginay
 Andi Vajda
 Case Van Horsen
 John Mark Vandenberg
diff --git a/Misc/NEWS.d/next/Library/2019-07-31-16-49-01.bpo-37723.zq6tw8.rst b/Misc/NEWS.d/next/Library/2019-07-31-16-49-01.bpo-37723.zq6tw8.rst
new file mode 100644
index 000000000000..65507bd0dc91
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-07-31-16-49-01.bpo-37723.zq6tw8.rst
@@ -0,0 +1,2 @@
+Fix performance regression on regular expression parsing with huge
+character sets. Patch by Yann Vaginay.
\ No newline at end of file