[LabPython-Users] comments on labpython (WORKING with LV2010/python 2.7.1)

[Enrico S. <enr...@we...>]

In this message
http://lavag.org/topic/8137-labpython-error-message/page__view__findpost__p__48425
Rolf Kalbermatter complained about very low feedback about labpython, and mostly in the form of "help me it doesn't work" by random users.

I'd like to mend for that and submit a few comments. Labpython works for me and is great, and helps me integrating in a big LV frame some image processing code written earlier in python. I'm essentially illitterate in python and trying to pick up quickly.

I'm using labpython in LV2010sp1 (yes it works!), with python 2.7.1 together with some modules, which at the moment are numpy 1.6.1 and matplotlib 1.0.1 (both just installed from the respective windows installers, no need to set paths, anything) and openCV 2.2.0 (just needed to copy the two files cv.lib and cv.pyd to Python 2.7\Lib\site-packages\). Platform is Windows7/32bit (and pity linux is not supported...)

I have a couple of comments though:

1) there seems to be a name visibility problem, or maybe a strict private variable enforcement (? -- my python ignorance), such that functions cannot see variables defined outside them (this is different than in IDLE).
Notably, this produces errors like 
"PYTHON Execute Script__ogtk.vi->xxxxx.vi:<type 'exceptions.NameError'>, global name 'yyyy' is not defined", and seems to be what people trying to use modules stumble upon. The problem has been already reported earlier (http://forums.ni.com/t5/LabVIEW/LabPython-Global-Variables/m-p/1481590/highlight/false
http://forums.openg.org/index.php?showtopic=1152
http://lavag.org/topic/12661-importing-modules/page__hl__labpython__fromsearch__1 ); I stumbled on it at first, but worked around it by declaring the necessary modules and variables global.

2) I find that the error messages reported by the labpython script note and by PYTHON Execute script.vi miss what would be very useful information for debugging - the call stack or at least the offending python line number. Luaview reports such information (in fact, contrary to LV convention of reporting only the source vi in the error cluster), and there is very useful. Luaview and labpython share the same author IIUC...

3) I found one case, whith a 160 line python script which imports modules, in which the first call to PYTHON Execute script.vi takes significantly more time than subsequent calls, *despite the fact that the script is precompiled*. The test is done by the BD attached, and the overhead for the first call is some 600ms. Is there an explanation for the fact?

Enrico

PS for Rolf - I'm also perusing luaview (win & linux) in another project of mine - KEEP UP THE GOOD WORK!