How to debug npyscreen application?

[Федор Белов]

Hello. I'm not Python developer - my main language is Java. I would like to implement console application so I choosed npyscreen. I've got one problem - how to debug my application? It tried to use PyCharm but it failed to run it.

[Itamar Gal]

Hey Федор Белов,

I use Unix (Linux and Mac OS X) exclusively, so I don't know what to do on Windows. I've been redirecting standard output and standard error to files, and that's been working pretty well for me:

# Redirect stdout and stderr to files
import sys
sys.stdout = open('stdout.log', 'w')
sys.stderr = open('stderr.log', 'w')

For fancier logging you might want to take a look at the logging and the traceback modules. You might also want to check out the winpdb debugger for live debugging, although I haven't really used it for anything yet, so I can't say very much about it.

- Itamar

[Nicholas Cole]

Recent versions of npyscreen also allow you to script the input to the
application for testing purposes. See 'Writing Tests' in the
documentation.

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[Bobby Hines]

Itamar, where in your npyscreen code do you open the log files? When I try to do this it blocks the npyscreen application from launching. 

[Eris Diskordia]

I also liked to redirect STDERR to get a proper Error Logging. The problem is that npyscreen gets the screensize from the stderr fileio. Dunno why.

my quick&dirty fix was in line 117 in file /usr/local/lib/python2.7/dist-packages/npyscreen/proto_fm_screen_area.py

change

mxy, mxx = struct.unpack('hh', fcntl.ioctl(sys.stderr.fileno(), termios.TIOCGWINSZ, 'xxxx'))

to

mxy, mxx = struct.unpack('hh', fcntl.ioctl(sys.stdout.fileno(), termios.TIOCGWINSZ, 'xxxx'))

then you can redirect stderr to a file and leave stdout on the screen for the npyscren/ncurses application.

I am not at the actual version so maybe the line is on another linenumer ... but its exactly the line you would see in the error message.

[Nicholas Cole]

I'll apply that fix in the main code. Thank you.

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