[PyQt] No errors reported by deployed application, no functionality either

[Kyle Altendorf]

On 2016-02-07 15:02, Kyle Altendorf wrote:
> On 2016-02-06 19:57, michael h wrote:
>> Have you tried something like:
>> 
>> myapp.exe > out.txt 2>&1
>> 
>> from cmd?
> 
> Very interesting.  That did help it out and the expected messages
> showed up in `out.txt`.  I tried checking all encodings in pyqtdeploy
> (except the Japanese that seemed to not be present in my Python
> install) but that didn't help.  I had previously added cp1252 (IIRC)
> when that was complained about being missing while running from within
> pyqtdeploy.
> 
> So, with this ability to see the messages I was able to get a messy
> but functional .pdy file that creates a `result` directory I can copy
> to a clean virtual machine and run.  Well, I did have to install
> drivers for my CAN adapter, but that's expected.  Thanks so much for
> the help.  I guess I have to continue digging into what is wrong with
> stdout.  Perhaps it is a Win10 issue?  At least it is recreatable and
> without pyqtdeploy or PyQt at all, I think.  This exact command prints
> in Cygwin but exits silently and with a 0 exit code (%errorlevel%) in
> cmd.exe.  Redirecting does not help in this case though, so maybe not
> quite the same.
> 
> "c:/python34/python" -c 'print("blue")'

Aside from the apparent quoting error in this line and it's total lack 
of relationship to my problem...  I did figure out and fix [1] my 
underlying issue.

My issue was introduced when I was initially getting pyqtdeploy working 
because I added sys.stdout.Flush() as a diagnostic attempt when no 
messages were printed to the screen and then did not remove it after 
solving those other issues.  The result at first was that when the 
application was deployed as a GUI, sys.stdout was None and hence an 
exception was thrown.  Without any stdout, the exception had nowhere to 
be reported.  Later I added the GUI exception dialog but 
sys.stdout.flush() was called before I created my QApplication() so 
another exception was thrown when I attempted to launch the 
QMessageBox() to report the first exception.  But, it seems to all be 
unwound now.

I'm not sure but this may relate in some way to Python issue #17797 [2].

As always, thanks for the help.  I would say that I hope this will help 
someone else but I bet there aren't too many out there pointlessly 
flushing sys.stdout in their GUI applications...

Cheers,
-kyle


[1] 
https://github.com/altendky/st/commit/fda167f20081ba0f24293d71535b68b2e6954bb0
[2] 
https://riverbankcomputing.com/pipermail/pyqt/2015-January/035442.html