[Python-Dev] Incorrect documentation of the raw_input built-in function
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? ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Incorrect documentation of the raw_input built-in function
pobox.com> writes: > > > Isaac> Have people actually verified that the prompt is really sent to > Isaac> stderr right now by using 2>/dev/null to attempt to suppress it? > > Good point. On my machine at work (Solaris), Python 2.4 seems to send its > raw_input prompt to stdout, not stderr: > > > Same for 2.6a0 on my Mac at home. Mike, are you sure about it prompting to > stderr? If so, what's your setup? > > Skip Skip, Guido and others: 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. ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Incorrect documentation of the raw_input built-in function
Guido van Rossum python.org> writes: > > > 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. > Being that Guido agrees, should I put a bug report into the system for it, and if so, which should it report as the bug: the actual behavior of the raw_input prompt when GNU readline is not installed, or the documentation? ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
