diff --git a/common/lib/xmodule/xmodule/abtest_module.py b/common/lib/xmodule/xmodule/abtest_module.py
index bb55fa7ee8..035413a402 100644
--- a/common/lib/xmodule/xmodule/abtest_module.py
+++ b/common/lib/xmodule/xmodule/abtest_module.py
@@ -11,18 +11,19 @@ DEFAULT = "_DEFAULT_GROUP"
 
 
 def group_from_value(groups, v):
-    ''' Given group: (('a',0.3),('b',0.4),('c',0.3)) And random value
+    """
+    Given group: (('a', 0.3), ('b', 0.4), ('c', 0.3)) and random value v
     in [0,1], return the associated group (in the above case, return
-    'a' if v<0.3, 'b' if 0.3<=v<0.7, and 'c' if v>0.7
-'''
+    'a' if v < 0.3, 'b' if 0.3 <= v < 0.7, and 'c' if v > 0.7
+    """
     sum = 0
     for (g, p) in groups:
         sum = sum + p
         if sum > v:
             return g
 
-    # Round off errors might cause us to run to the end of the list
-    # If the do, return the last element
+    # Round off errors might cause us to run to the end of the list.
+    # If the do, return the last element.
     return g