diff --git a/engine/singleton.py b/engine/singleton.py
index 53b0b87..b9b24f9 100644
--- a/engine/singleton.py
+++ b/engine/singleton.py
@@ -3,7 +3,7 @@ class Singleton(type):
         super(Singleton, cls).__init__(name, bases, dict)
         cls.instance = None
 
-    def __call__(cls,*args,**kw):
+    def __call__(cls, *args, **kw):
         if cls.instance is None:
             cls.instance = super(Singleton, cls).\
                 __call__(*args, **kw)