New submission from Skip Montanaro: >From a thread on python-dev...
http://mail.python.org/pipermail/python-dev/2008-January/076446.html Mike Kent mike.kent at sage.com Thu Jan 24 16:33:47 CET 2008 Recently I was trying to debug an old python program who's maintenance I inherited. I was using the quick-and-dirty method of putting some 'print >>sys.stderr' statements in the code, and then running the command with '2>filename' appended to the end of the command line. Imagine my surprise to see that all of the prompt text from the program's raw_input calls were also disappearing from the screen output, and appearing in the stderr output routed to the file. The latest documentation for raw_input states "If the prompt argument is present, it is written to standard output without a trailing newline." I posted a question regarding the observed behavior to comp.lang.python and Gabriel Genellina (thanks Gabriel!) pointed out that despite the documentation, raw_input was hard-coded to always output its prompt text to stderr. This raises two questions: 1. Shouldn't the current documentation be corrected to state that raw_input writes its prompt to standard error? 2. Is this really the hard-coded behavior we want? I don't think my use-case is that odd; in fact, what I find very odd is that the prompt output is send to stderr. I mean, I'm printing the prompt for a question, not some error message. Can there not at least be an optional parameter to indicate that you want the output sent to stdout rather than stderr? ... after a few responses ... Guido van Rossum guido at python.org Thu Jan 24 21:09:12 CET 2008 On Jan 24, 2008 11:41 AM, Mike Kent <mike.kent at sage.com> wrote: ... > Interesting point about whether GNU readline is installed. My setup is RedHat > Linux, with Python 2.5 that I built and installed myself. GNU readline is not, > in fact, installed. If you look at Python2.5/Parser/myreadline.c, function > PyOS_StdioReadline, line 125, you will see that prompt output is being sent to > stderr. As best as my Python-fu can determine, this is the code used to output > a raw_input prompt (thanks again to Gabriel Genellina for pointing me in the > right direction.) > > It's entirely likely that the difference in what I am seeing and what you guys > are seeing is caused by my not having GNU readline installed. Nevertheless, > the behavior without it seems wrong, and is certainly different from the > documentation. Agreed. ---------- components: Interpreter Core messages: 61652 nosy: skip.montanaro severity: normal status: open title: raw_input behavior incorrect if readline not enabled versions: Python 2.5, Python 2.6 __________________________________ Tracker <[EMAIL PROTECTED]> <http://bugs.python.org/issue1927> __________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
