From 18ad02f6a454f6f1ac0bfb948cc2a9fc09237f32 Mon Sep 17 00:00:00 2001
From: Thomas Wiecki <thomas.wiecki@gmail.com>
Date: Wed, 22 Oct 2014 15:41:16 +0200
Subject: [PATCH] MAINT: Make len check for ffillable explicit.

---
 zipline/history/history_container.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/zipline/history/history_container.py b/zipline/history/history_container.py
index 8793cec2..02163264 100644
--- a/zipline/history/history_container.py
+++ b/zipline/history/history_container.py
@@ -490,7 +490,7 @@ class HistoryContainer(object):
         Store the non-NaN values from our oldest frame in each frequency.
         """
         ffillable = self.ffillable_fields
-        if not ffillable:
+        if len(ffillable) == 0:
             return
 
         for frequency in self.unique_frequencies: