Sorry for my duplicate comment. It was a mistake. On closer examination, the OP's description does seem to indicate some issue. Please look at (attached) stdin_noiter.py which uses readline() directly and it does not have the problem described here. It properly detects EOF on first CTRL-D. This points to some problem with the iterator function fileobject.c:file_iternext(). I think that the first CTRL-D might be getting lost somewhere in the read ahead code (which only comes into picture with iterator).