While trying to test the patch for http://bugs.python.org/issue5492 on Windows, I discovered that quit() and exit() in the Idle Shell are now disabled, it seems, for all versions on all systems rather than just sometimes on Linux. The problem is a change in idlelib that invalidated an assumption made in site.py. Revs 81718-81721 for http://bugs.python.org/issue9290 changed idlelib.PyShell.PseudoFile (line 1277 in 3.3) to subclass io.TextIOBase, which subclasses IOBase. This gave PseudoFile and its subclasses a .fileno instance method attribute that raises io.UnsupportedOperation: fileno. This is not a bug since the doc for io.IOBase.fileno says: "Return the underlying file descriptor (an integer) of the stream if it exists. An OSError is raised if the IO object does not use a file descriptor." (the particular error raised is not an issue here). This is the code for Quitter.__call__ in site.py (line 368 in 3.3): def __call__(self, code=None): # Shells like IDLE catch the SystemExit, but listen when # stdin wrapper is closed. try: fd = -1 if hasattr(sys.stdin, "fileno"): fd = sys.stdin.fileno() if fd != 0: # Don't close stdin if it wraps fd 0 sys.stdin.close() except: pass raise SystemExit(code) The incorrect assumption is that if sys.stdin.fileno exits but raises, the call did not come from a shell that needs .close called. I do not know enough about other circumstances in which stdin.fileno would do something other than return 0 to be sure of what the proper fix would be. (I increasingly dislike bare excepts as they hide the thinking and knowledge of the original programmer. What exception was expected that should be passed away?) Given that the callable constants exit and quit and are optionally suppressed on startup and are not standard builtins http://docs.python.org/3/library/constants.html#constants-added-by-the-site-... it would be alright with me to ignore this regression and release as scheduled. But I though people should be aware of it. -- Terry Jan Reedy