corrected wrong logic of the routine

pylot/core/read/data.py

@@ -85,11 +85,11 @@ class Data(object):
             raise FormatError(errmsg)
 
         if fnout is None:
-            ID = self.evtdata.getEventID()
-        else:
             ID = self.getID()
             # handle forbidden filenames especially on windows systems
             fnout = fnConstructor(ID)
+        else:
+            fnout = fnConstructor(fnout)
 
         evtformat = evtformat.upper().strip()