I am presuming 2.7 has same problem since it has same code. The patch appears to give PyShell.close a return value it did not have before. Perhaps remove the return? I am slightly puzzled: self.pollinterval is 50 (millisecs). If reducing the wait from 100 to 1 makes the problem constant, why does reducing it to 0 make it go away? What have I misunderstood? Trying to test on Windows in a 3.3 build, I get the following with or without the patch: >>> exit() Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> exit() File "D:\Python\dev\py33\lib\site.py", line 380, in __call__ raise SystemExit(code) SystemExit: None -------------------------------- 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) >>> --------------------------- <bare excepts are evil> ---------------------------- >>> import sys >>> hasattr(sys.stdin, "fileno") True >>> sys.stdin.fileno <built-in method fileno of PseudoInputFile object at 0x02893C08> >>> sys.stdin.fileno() Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> sys.stdin.fileno() io.UnsupportedOperation: fileno The problem is that PseudoInputFile subclasses PseudoFile which now subclasses TestIOBase without overriding .fileno(), which raises the above. This is from #9290. Bottom line: I believe quit() and exit() are broken in the current 2.7, 3.2, and 3.3 rc's. I will report a possible quick fix on pydev.