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The following code works on Python versions prior to 3.3a1:
import curses
def test_screen(screen):
 screen.addch(5,5, curses.ACS_HLINE)
 screen.refresh()
curses.wrapper(test_screen)
On python3.3, the program produces the following traceback:
Traceback (most recent call last):
 File "/tmp/p.py", line 7, in <module>
 curses.wrapper(test_screen)
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/curses/__init__.py", line 94, in wrapper
 return func(stdscr, *args, **kwds)
 File "/tmp/p.py", line 4, in test_screen
 screen.addch(5,5, curses.ACS_HLINE)
OverflowError: byte doesn't fit in chtype

Marking as release blocker since this is a regression. Added people from the other curses issue as being likely to be interested in this one.

New changeset 861a5f3e7453 by Victor Stinner in branch 'default':
Close #14223: curses.addch() is no more limited to the range 0-255 when the
http://hg.python.org/cpython/rev/861a5f3e7453 

I introduced the arbitrary limit when I added support of the curses Unicode API (libncursesw). The limit is useless if libncursesw is used, whereas it blocks legal "characters" like KEY_xxx constants. So I just removed the check and it should not be ok.
The real issue is that Python curses is not linked to libncursesw on Mac OS X!

I'm reopening this bug because I've noticed that in Python3.3rc1, although trying to print curses.ACS_HLINE and other such characters no long cause an Exception, only blank characters are printed to the screen.
Tested with both Terminal.App and xterm running under XQuartz.
Here is some minimal test code, that will print a line on Python2.x but a blank screen on Python3.3rc1.

import curses
def test_screen(screen):
 screen.addch(5,5, curses.ACS_HLINE)
 screen.addch(5,6, curses.ACS_HLINE)
 screen.refresh()
 curses.napms(2000)
curses.wrapper(test_screen)

New changeset 27b5bd5f0e4c by Victor Stinner in branch 'default':
Close #14223: Fix window.addch(curses.ACS_HLINE)
http://hg.python.org/cpython/rev/27b5bd5f0e4c 

> I'm reopening this bug because I've noticed that in Python3.3rc1,
> although trying to print curses.ACS_HLINE and other such characters
> no long cause an Exception, only blank characters are printed to
> the screen.
If the Python curses module is compiled in Unicode mode (if curses.unget_wch() is present), addch(int) calls the C function wadd_wch() or mvwadd_wch(), instead of waddch() or mvwaddch(). It looks like the *_wch() family does not support characters like curses.ACS_HLINE.
My commit fixes the issue.
@Nicholas.Cole: Can you please try the last development version (default branch)?
@georg.brandl: Can you please include the important fix 27b5bd5f0e4c in Python 3.3 final?

(keep the issue open until the fix is included in Georg's repository)

Unless I'm getting the build process wrong (possible, because I haven't tried testing fixes before), this fix isn't working for me.

> Unless I'm getting the build process wrong (possible, because
> I haven't tried testing fixes before), this fix isn't working for me.
Oh did you compile Python? Did you install it?
Do you have libncursesw? => do you have the function curses.unget_wch?
What is the version of your libcurses[w] library? There are issues on libncurses 5.7. I think Ned Bat changed the script to compile Python on Mac to use a builtin copy of libncurses 5.9. See:
http://bugs.python.org/issue14225#msg163323 

> Unless I'm getting the build process wrong (possible, because
> I haven't tried testing fixes before), this fix isn't working for me.
Oh did you compile Python? Did you install it?
Yes, I tried compiling it. 
#./configure MACOSX_DEPLOYMENT_TARGET=10.8 --enable-framework --with-universal-archs="64-bit" CFLAGS="-arch x86_64" LDFLAGS="-arch x86_64" && make -j6 && make install
Do you have libncursesw? => do you have the function curses.unget_wch?
yes...
Python 3.3.0rc1+ (default, Sep 3 2012, 09:45:35) 
[GCC 4.2.1 Compatible Apple Clang 4.0 ((tags/Apple/clang-421.0.57))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import curses
>>> curses.unget_wch()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
_curses.error: must call initscr() first
>>> curses.version
b'2.2'
>>> 
What is the version of your libcurses[w] library? There are issues on libncurses 5.7. I think Ned Bat changed the script to compile Python on Mac to use a builtin copy of libncurses 5.9. See:
http://bugs.python.org/issue14225#msg163323
How do I check which version it was built against? The messages from ./configure just say that the tests pass, not which version it has found.

> How do I check which version it was built against?
On Linux, I use:
$ ldd /usr/lib/python2.7/lib-dynload/_curses.so |grep curses
 libncursesw.so.5 => /lib/i386-linux-gnu/libncursesw.so.5 (0xb76d0000)
$ ls -l /lib/i386-linux-gnu/libncursesw.so.5
lrwxrwxrwx 1 root root 18 nov. 18 2011
/lib/i386-linux-gnu/libncursesw.so.5 -> libncursesw.so.5.9
=> version 5.9

On Mon, Sep 3, 2012 at 3:15 PM, STINNER Victor <report@bugs.python.org> wrote:
>
> STINNER Victor added the comment:
>
>> How do I check which version it was built against?
>
> On Linux, I use:
>
> $ ldd /usr/lib/python2.7/lib-dynload/_curses.so |grep curses
> libncursesw.so.5 => /lib/i386-linux-gnu/libncursesw.so.5 (0xb76d0000)
> $ ls -l /lib/i386-linux-gnu/libncursesw.so.5
> lrwxrwxrwx 1 root root 18 nov. 18 2011
> /lib/i386-linux-gnu/libncursesw.so.5 -> libncursesw.so.5.9
>
> => version 5.9
I get Version 5.4, which seems very out of date (I'm running the
latest release of OS X) but:
nicholas$ ls -l /usr/lib/libncurses.
libncurses.5.4.dylib libncurses.5.dylib libncurses.dylib
NPSC:mnpyscreen nicholas$ ls -l /usr/lib/libncurses.dylib
lrwxr-xr-x 1 root wheel 20 25 Jul 18:32 /usr/lib/libncurses.dylib
-> libncurses.5.4.dylib
nicholas$ ldd /usr/lib/python2.7/lib-dynload/_curses.so |grep curses
/usr/lib/python2.7/lib-dynload/_curses.so:
	/usr/lib/libncurses.5.4.dylib (compatibility version 5.4.0, current
version 5.4.0)
Can that possibly be right??

> Can that possibly be right??
Yes. That's the version of ncurses that Apple ships with current versions of OS X. You can build it yourself and install into /usr/local and rebuild python. For ncurses 5.9, something like:
./configure --enable-widec --enable-shared --with-shared --without-normal
&& make && sudo make install
should work. FWIW, when I run your test script with tip, I now do see the two horizontal bars.

Done in d6d632f254ee.

New changeset d6d632f254ee by Victor Stinner in branch 'default':
Close #14223: Fix window.addch(curses.ACS_HLINE)
http://hg.python.org/cpython/rev/d6d632f254ee 

I've just tried the OS X build of 3.3rc2, and this has been fixed. Thank you!

> I've just tried the OS X build of 3.3rc2, and this has been fixed. Thank you!
Great!