From 03dc78f5c4cb6c5179ea0f20ff608f7db2036976 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 26 Sep 2017 17:51:55 +0300
Subject: [PATCH 1/2] bpo-28293: The regex cache no longer completely dump when
 full.

---
 Lib/re.py                                          | 14 ++++++++++++--
 .../2017-09-26-17-51-17.bpo-28293.UC5pm4.rst       |  1 +
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst

diff --git a/Lib/re.py b/Lib/re.py
index d0ee5db175b5fa..657a4f6721ed59 100644
--- a/Lib/re.py
+++ b/Lib/re.py
@@ -128,6 +128,13 @@
 except ImportError:
     _locale = None
 
+# try _collections first to reduce startup cost
+try:
+    from _collections import OrderedDict
+except ImportError:
+    from collections import OrderedDict
+
+
 # public symbols
 __all__ = [
     "match", "fullmatch", "search", "sub", "subn", "split",
@@ -260,7 +267,7 @@ def escape(pattern):
 # --------------------------------------------------------------------
 # internals
 
-_cache = {}
+_cache = OrderedDict()
 
 _pattern_type = type(sre_compile.compile("", 0))
 
@@ -281,7 +288,10 @@ def _compile(pattern, flags):
     p = sre_compile.compile(pattern, flags)
     if not (flags & DEBUG):
         if len(_cache) >= _MAXCACHE:
-            _cache.clear()
+            try:
+                _cache.popitem(False)
+            except KeyError:
+                pass
         _cache[type(pattern), pattern, flags] = p
     return p
 
diff --git a/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst b/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst
new file mode 100644
index 00000000000000..4c70e2424df65f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst
@@ -0,0 +1 @@
+The regex cache no longer completely dump when full.

From 7aaa5b7d547c94e59a7e51abc7f530280e817e0d Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Tue, 26 Sep 2017 19:27:13 +0300
Subject: [PATCH 2/2] Improve wording.

---
 .../next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst       | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst b/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst
index 4c70e2424df65f..16b92b05dbf630 100644
--- a/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst
+++ b/Misc/NEWS.d/next/Library/2017-09-26-17-51-17.bpo-28293.UC5pm4.rst
@@ -1 +1 @@
-The regex cache no longer completely dump when full.
+The regular expression cache is no longer completely dumped when it is full.