From 457ac2630c2be55039ad68eaac2d629a6610afdb Mon Sep 17 00:00:00 2001
From: Eddie Hebert <ehebert@quantopian.com>
Date: Fri, 20 Dec 2013 12:41:51 -0500
Subject: [PATCH] BUG: Make BarData iterkeys method match dict iterkeys
 behavior.

Use a generator, instead of creating a list.
---
 zipline/protocol.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/zipline/protocol.py b/zipline/protocol.py
index 4834fb64..1f1e3ba2 100644
--- a/zipline/protocol.py
+++ b/zipline/protocol.py
@@ -171,7 +171,7 @@ class BarData(object):
 
     def iterkeys(self):
         # Allow contains override to filter out sids.
-        return [sid for sid in self._data.iterkeys() if sid in self]
+        return (sid for sid in self._data.iterkeys() if sid in self)
 
     def keys(self):
         # Allow contains override to filter out sids.