2009/9/30 Robert Kern <robert.k...@gmail.com>:
> I am blissfully unaware of the problems Paul mentioned about Windows GUI-mode
> programs.
:-)
> I'm not sure what would make a program "GUI-mode" or not. Certainly, I have
> written
> Python programs that use wxPython and PyQt on Windows that print to
> stdout/stderr,
> and they appear to work fine.
It's the difference between using python.exe and pythonw.exe. There's
a flag in the executable header saying whether the executable is
"console mode" or "gui mode".
GUI mode programs are run (by the OS) without a console (or if run
from a console prompt, they automatically detach from that console,
much like Unix programs which fork themselves to leave the terminal
group (did I get the terminology right?) but done by the OS). As a
result, the program has no valid stdin/out/err handles. Any attempt to
write to them causes the program to crash.
Traceback (most recent call last):
File "hello.py", line 13, in <module>
main()
File "hello.py", line 7, in main
sys.stdout.flush()
IOError: [Errno 9] Bad file descriptor
(Question - is it *ever* possible for a Unix program to have invalid
file descriptors 0,1 and 2? At startup - I'm assuming anyone who does
os.close(1) knows what they are doing!)
Paul.
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