From 38ae8bbb675c33ab95009acace9fd1c7eb6c46c0 Mon Sep 17 00:00:00 2001
From: Eddie Hebert <ehebert@quantopian.com>
Date: Mon, 29 Apr 2013 14:34:50 -0400
Subject: [PATCH] BUG: Ensure that window length value is sanity checked.

When moving BatchTransform off of EventWindow as a base object,
the checking of window length was lost, restore that check using
the same function as EventWindow.
---
 zipline/transforms/utils.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/zipline/transforms/utils.py b/zipline/transforms/utils.py
index d9799e51..c8a431e1 100644
--- a/zipline/transforms/utils.py
+++ b/zipline/transforms/utils.py
@@ -367,7 +367,10 @@ class BatchTransform(object):
         self.field_names = set()
 
         self.refresh_period = refresh_period
+
+        check_window_length(window_length)
         self.window_length = window_length
+
         self.trading_days_total = 0
         self.window = None