Bugs item #1633941, was opened at 2007-01-12 05:34 Message generated for change (Comment added) made by draghuram You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1633941&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Python Library Group: Python 2.5 Status: Open Resolution: None Priority: 5 Private: No Submitted By: Matthias Klose (doko) Assigned to: Nobody/Anonymous (nobody) Summary: for line in sys.stdin: doesn't notice EOF the first time Initial Comment: [forwarded from http://bugs.debian.org/315888] for line in sys.stdin: doesn't notice EOF the first time when reading from tty. The test program: import sys for line in sys.stdin: print line, print "eof" A sample session: [EMAIL PROTECTED] python foo.py foo <--- I pressed Enter and then Ctrl-D foo <--- then this appeared, but not more eof <--- this only came when I pressed Ctrl-D a second time [EMAIL PROTECTED] Seems to me that there is some buffering issue where Python needs to read end-of-file twice to notice it on all levels. Once should be enough. ---------------------------------------------------------------------- Comment By: Raghuram Devarakonda (draghuram) Date: 2007-01-24 12:20 Message: Logged In: YES user_id=984087 Originator: NO I tested two kinds of inputs with iter and noiter verisons. I posted "noter" code and OP's code is the iter version. 1) For input without newline at all (line1<CTRL-D><CTRL-D><CTRL-D>) behaves same with both versions. 2) The noiter version prints "eof" with "line1\n<CTRL-D>" while the iter version requires an additional CTRL-D. This is because iter version uses read ahead which is implemented using fread() . A simple C program using fread() behaves exactly same way. I tested on Linux but am sure windows behaviour (as posted by gagenellina) will have same reasons. Since the issue is with platform's stdio library, I don't think python should fix anything here. However, it may be worthwhile to mention something about this in documentation. I will open a bug for this purpose. ---------------------------------------------------------------------- Comment By: Raghuram Devarakonda (draghuram) Date: 2007-01-22 12:45 Message: Logged In: YES user_id=984087 Originator: NO Ok. This may sound stupid but I couldn't find a way to attach a file to this bug report. So I am copying the code here: ************ import sys line = sys.stdin.readline() while (line): print line, line = sys.stdin.readline() print "eof" ************* ---------------------------------------------------------------------- Comment By: Raghuram Devarakonda (draghuram) Date: 2007-01-22 12:37 Message: Logged In: YES user_id=984087 Originator: NO 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). ---------------------------------------------------------------------- Comment By: Raghuram Devarakonda (draghuram) Date: 2007-01-22 11:34 Message: Logged In: YES user_id=984087 Originator: NO I am not entirely sure that this is a bug. $ cat testfile line1 line2 $ python foo.py < testfile This command behaves as expected. Only when the input is from tty, the above described behaviour happens. That could be because of the terminal settings where characters may be buffered until a newline is entered. ---------------------------------------------------------------------- Comment By: Raghuram Devarakonda (draghuram) Date: 2007-01-22 11:34 Message: Logged In: YES user_id=984087 Originator: NO I am not entirely sure that this is a bug. $ cat testfile line1 line2 $ python foo.py < testfile This command behaves as expected. Only when the input is from tty, the above described behaviour happens. That could be because of the terminal settings where characters may be buffered until a newline is entered. ---------------------------------------------------------------------- Comment By: Gabriel Genellina (gagenellina) Date: 2007-01-13 23:20 Message: Logged In: YES user_id=479790 Originator: NO Same thing occurs on Windows. Even worse, if the line does not end with CR, Ctrl-Z (EOF in Windows, equivalent to Ctrl-D) has to be pressed 3 times: D:\Temp>python foo.py foo <--- I pressed Enter ^Z <--- I pressed Ctrl-Z and then Enter again foo <--- this appeared ^Z <--- I pressed Ctrl-Z and then Enter again <EOF> D:\Temp>python foo.py foo^Z <--- I pressed Ctrl-Z and then Enter ^Z <--- cursor stays here; I pressed Ctrl-Z and then Enter again ^Z <--- cursor stays here; I pressed Ctrl-Z and then Enter again foo <EOF> ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1633941&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
