[Python-checkins] cpython: Issue #21448: Improve performance of the email feedparser

[raymond.hettinger]

https://hg.python.org/cpython/rev/830bcf4fb29b
changeset:   96223:830bcf4fb29b
user:        Raymond Hettinger <python at rcn.com>
date:        Fri May 22 17:23:28 2015 -0700
summary:
  Issue #21448: Improve performance of      the email feedparser

files:
  Lib/email/feedparser.py |  16 ++++++++--------
  1 files changed, 8 insertions(+), 8 deletions(-)


diff --git a/Lib/email/feedparser.py b/Lib/email/feedparser.py
--- a/Lib/email/feedparser.py
+++ b/Lib/email/feedparser.py
@@ -26,6 +26,7 @@
 from email import errors
 from email import message
 from email._policybase import compat32
+from collections import deque
 
 NLCRE = re.compile('\r\n|\r|\n')
 NLCRE_bol = re.compile('(\r\n|\r|\n)')
@@ -52,8 +53,8 @@
     def __init__(self):
         # Chunks of the last partial line pushed into this object.
         self._partial = []
-        # The list of full, pushed lines, in reverse order
-        self._lines = []
+        # A deque of full, pushed lines
+        self._lines = deque()
         # The stack of false-EOF checking predicates.
         self._eofstack = []
         # A flag indicating whether the file has been closed or not.
@@ -78,21 +79,21 @@
             return NeedMoreData
         # Pop the line off the stack and see if it matches the current
         # false-EOF predicate.
-        line = self._lines.pop()
+        line = self._lines.popleft()
         # RFC 2046, section 5.1.2 requires us to recognize outer level
         # boundaries at any level of inner nesting.  Do this, but be sure it's
         # in the order of most to least nested.
-        for ateof in self._eofstack[::-1]:
+        for ateof in reversed(self._eofstack):
             if ateof(line):
                 # We're at the false EOF.  But push the last line back first.
-                self._lines.append(line)
+                self._lines.appendleft(line)
                 return ''
         return line
 
     def unreadline(self, line):
         # Let the consumer push a line back into the buffer.
         assert line is not NeedMoreData
-        self._lines.append(line)
+        self._lines.appendleft(line)
 
     def push(self, data):
         """Push some new data into this object."""
@@ -119,8 +120,7 @@
         self.pushlines(parts)
 
     def pushlines(self, lines):
-        # Reverse and insert at the front of the lines.
-        self._lines[:0] = lines[::-1]
+        self._lines.extend(lines)
 
     def __iter__(self):
         return self

-- 
Repository URL: https://hg.python.org/cpython