diff --git a/script/Electric_field_loop.py b/script/Electric_field_loop.py
index 7b42997..e724a5b 100644
--- a/script/Electric_field_loop.py
+++ b/script/Electric_field_loop.py
@@ -34,7 +34,7 @@ Noavg = 5;
 #forward loop
 
 file_prefix = time.strftime("%y%m%d")
-filename.open("data"+file_prefix,"a")
+filename.open("data"+file_prefix+".txt","a")
 for i in range(0,No_of_steps):
     B = -Max +2*i*dB;
     print "Setting field = ", B