raw_input(), STRANGE behaviour
I ran into a very strange behaviour of raw_input().
I hope somebody can tell me how to fix this.
(Or is this a problem in the python source?)
I will explain the problem by using 3 examples. (Sorry, long email)
The first two examples are behaving normal, the thirth is
strange...
I wrote the following flabbergasting code:
#-
print "1: This is the print statement."
# Now halt the program until someone hits enter
raw_input("2: This is the raw_input prompt.")
import sys
print "3: This is a possible solution. ",
sys.stdout.flush()
command = sys.stdin.readline()
#-
and saved it in the file 'script.py'.
*** First, normal behaviour to stdout
Now, I open a command line and run the following command:
python script.py
On screen appears, after a few 'enter' keys:
1: This is the print statement.
2: This is the raw_input prompt.
3: This is a possible solution.
All works fine..
*** Second, redirected stdout to file, normal behaviour.
>From the command prompt I run:
python script.py > stdout_catch.txt
The screen stays empty, and after a few 'enter' keys the prompt
reapears.
In the file 'stdout_catch.txt' are the lines:
1: This is the print statement.
2: This is the raw_input prompt.
3: This is a possible solution.
And again, all works fine..
*** Thirst, redirect stderr to file, STRANGE behaviour..
>From the command prompt I run:
python script.py 2> stderr_catch.txt
This should redirect strerr to the file and stdout should stay on the
screen.
But. What happens?
After a few 'enter' keys, on screen apears:
1: This is the print statement.
3: This is a possible solution.
WHERE IS THE SECOND LINE?
It is in the file stderr_catch.txt!!!
See the problem?
Please Tell me? Why is the prompt produced by raw_input() printed to
the error channel? It should be stdout, just as the print statement
does.
Looking at the python source code on
http://svn.python.org/view/python/tags/r251/Python/bltinmodule.c?rev=54864&view=auto
[found: 'builtin_raw_input(PyObject *self, PyObject *args)'].
One thing that I notice is that the code checks whether stdin and
stdout are connected to a terminal ("isatty" function), but I do not
know why the prompt ends up on stderr then.
What is the solution?
I have noticed this behaviour under DOS in Windows XP, Windows 2000,
Windows 2003 Server, Windows vista, and Linux. How do I get
raw_input() to send it's prompt to stdout?
Friendly greetings
Rens
--
http://mail.python.org/mailman/listinfo/python-list
Re: raw_input(), STRANGE behaviour
Hello Mike, Thanks for your reply. Since I momentarily do not have the ability to build a new python executable, I would like to ask for your help in this case. Are you able to supply me with a corrected version? Friendly greetings Rens Duijsens On 26 jan, 16:50, Mike Kent <[EMAIL PROTECTED]> wrote: > On Jan 26, 7:23 am, Dox33 <[EMAIL PROTECTED]> wrote: > > > > > > > I ran into a very strange behaviour of raw_input(). > > I hope somebody can tell me how to fix this. > ===CUT=== > > *** Thirst, redirect stderr to file, STRANGE behaviour.. > > From the command prompt I run: > > python script.py 2> stderr_catch.txt > > This should redirect strerr to the file and stdout should stay on the > > screen. > > > But. What happens? > > After a few 'enter' keys, on screen apears: > > 1: This is the print statement. > > 3: This is a possible solution. > > > WHERE IS THE SECOND LINE? > > It is in the file stderr_catch.txt!!! > > > See the problem? > > Please Tell me? Why is the prompt produced by raw_input() printed to > > the error channel? It should be stdout, just as the print statement > > does. > > I recently ran into this behaviour myself, and reported it both here > and to the python-dev mailing list. > Seehttp://groups.google.com/group/comp.lang.python/browse_thread/thread/... > > It turns out that *if* you don't have GNU readline installed, Python > falls back to its own implementation of readline, which is hard-coded > to send the prompt output to stderr. Guido agreed that this is wrong, > and a bug for it has been entered into the Python bug tracking > database. > > Your workaround until this bug is fixed is to install GNU readline, > and rebuild your python installation to use it rather than the fall- > back version.- Tekst uit oorspronkelijk bericht niet weergeven - > > - Tekst uit oorspronkelijk bericht weergeven - -- http://mail.python.org/mailman/listinfo/python-list
Re: raw_input(), STRANGE behaviour
Yes, I know. There are several ways to work around the problem. (Look at the innitial code I provided in this discussion start) Fact is, every time I'm getting a script from somewhere or someone, I have to search and replace all the affected code. Not very conveniant. That's why I rather would have a correct working version. On 27 jan, 04:20, Hrvoje Niksic <[EMAIL PROTECTED]> wrote: > Dox33 <[EMAIL PROTECTED]> writes: > > Thanks for your reply. Since I momentarily do not have the ability > > to build a new python executable, I would like to ask for your help > > in this case. Are you able to supply me with a corrected version? > > You can simply choose not to use raw_input, and use sys.stdin.readline > instead. Or define your own corrected raw_input: > > def my_raw_input(msg): > print msg, > return raw_input() -- http://mail.python.org/mailman/listinfo/python-list
Re: raw_input(), STRANGE behaviour
YES! This is what I was looking for. Great! All works fine now. Thank you very much Gabriel. Gabriel Genellina schreef: > Add this on your sitecustomize.py module (or create one) > > import sys > def raw_input(prompt=None): >if prompt: sys.stdout.write(prompt) >return original_raw_input() > > import __builtin__ > original_raw_input = __builtin__.raw_input > __builtin__.raw_input = raw_input > > It just replaces the builtin raw_input with a custom function. -- http://mail.python.org/mailman/listinfo/python-list
