Don't use range for performance reasons

diff --git a/tornado/stack_context.py b/tornado/stack_context.py
index 64c815f0e6936ef839f78637c961bd91a144ed5f..8804d42d88a096a591ff8e3d9e9aa3e6c888fa49 100644 (file)
--- a/tornado/stack_context.py
+++ b/tornado/stack_context.py
@@ -259,8 +259,9 @@ def wrap(fn):
                 exc = _handle_exception(top, exc)
             else:
                 # Otherwise take shorter path and run stack contexts in reverse order
-                for n in range(last_ctx - 1, -1, -1):
-                    c = stack[n]
+                while last_ctx > 0:
+                    last_ctx -= 1
+                    c = stack[last_ctx]
 
                     try:
                         c.exit(*exc)