Pythonscript show console on error

[Alan Kilborn]

Sometimes I run one of my pythonscripts and nothing happens – meaning the script function doesn’t happen. I’m left wondering why. Usually when this happens the Pythonscript console window isn’t active – or I’d see the Python error in red and know my script bombed out due to programmer error.

So I could probably “show” the pythonscript console as the first line in every script I write. That would get annoying, plus it is disruptive to workflow (I may have the Find Result panel active instead of the pythonscript console because I’m doing something with it).

So my question is, is it possible to install a “handler” such that if an unhandled python exception occurs, the Pythonscript console window is made active to make it obvious what has occurred? If so, how would I do such a thing?

[Claudia Frank]

@Alan-Kilborn

What comes first into my mind is to use always a main function and call it with
a try block, in the except part call console.show()
Intercepting exceptions in general would mean to register a function to sys.excepthook.

Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

Hello Claudia and thank you for your reply. I think using a main function with a try block could work, although it may get tiresome to always use it, plus I would forget to do it, but it is a good idea.

I was looking for a suggestion along the lines of your exception hook one. I remember researching this a while ago, and I could get it working under standard Python, but not as part of Pythonscript. I could register the hook but it wouldn’t get called. I could not figure out why. Unfortunately, as it was some time ago, I can’t remember any more details, if there were any to recall.

I would like to revisit it if anyone has any suggestions of a working example under Pythonscript…

[Claudia Frank]

@Alan-Kilborn

to be honest, I didn’t try it with python script yet.
Just thought it works. I should have known better ;-)
So, let’s start diggin’ - will follow up.

Cheers
Claudia

[Claudia Frank]

@Alan-Kilborn

ok - python script is using code.py to execute the scripts.
…\notepad++\plugins\PythonScript\lib\code.py

sys.excepthook can be overwritten to catch uncaught exceptions
unfortunately code.py does the following

    try:
        exec code in self.locals
    except SystemExit:
        raise
    except:
        self.showtraceback()
    else:
        if softspace(sys.stdout, 0):
            print

So there never will be an uncaught excpetion means we need to
comment the general except block then a script like

import sys

def my_logging_func(exctype, value, traceback):
    print 'got it'

sys.excepthook = my_logging_func

mport os  # missing the i on purpose to raise an exception

which gets executed returns got it

What I didn’t try is to import code and overwrite run_code function.
Leave it to you if you want to test this. ;-)

Cheers
Claudia

[Claudia Frank]

@Alan-Kilborn

Btw. a npp restart after modifying code.py is needed.

Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

I think you are a little bit advanced for me! :-)

So in code.py you mean do this:

#except:
    #self.showtraceback()

You totally lost me with: “What I didn’t try is to import code and overwrite run_code function.”

…but I will go have a look at code.py and try to figure out what you mean. Thank you again for your good (but a bit over my head at the moment) help.

[Claudia Frank]

@Alan-Kilborn

So in code.py you mean do this:

yes

You totally lost me with: “What I didn’t try is to import code and overwrite run_code function.”

In general python allows to overwrite what ever function if you use the same
function signature meaning same name and same number of arguments.
Namespaces (like what globals and locals do) could somehow try to protect function but if you try hard enough you can get it overwritten.

Depending how python script is loading code.py it could simply mean that if you
define your own runcode function you might overwrite the one from code.py.

Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

I tried to duplicate your “mport os” example, but I didn’t see “got it” – all I saw was the standard “SyntaxError: invalid syntax” traceback. I restarted N++ after commenting out the 2 lines in code.py.

I see what you mean now about overwriting the run_code function, but it seems like I could avoid that complexity and just copy+paste+modify the functionality of your “sys.excepthook = xxxxx_func” in startup.py and have that xxxxx_func function do what I want (e.g. console.show()) upon unhandled exception. Of course, currently since I don’t see the “got it” example working that is going to be problematic. :-)

[Claudia Frank]

@Alan-Kilborn

strange.

You do use python script 1.0.8?
On Windows or like me on linux?
Current npp version?

Cheers
Claudia

[Claudia Frank]

@Alan-Kilborn

wait - I guess I know why - just need to investigate why it didn’t happen to me.

Cheers
Claudia

[Claudia Frank]

Needs more investigation - will follow up on this tomorrow.

Good night
Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

Yes, using PS 1.0.8.0 on Win7. I renamed code.py (and deleted code.pyc) and restarted N++. I thought this would have really bad effects when trying to run PS’s in N++, but it had no effect at all (scripts ran just the same as always). This seems to indicate that code.py has no influence…but this is odd since you seem to see the effects of changing it. I’m confused…

[Alan Kilborn]

I’m hesitant to post this, because I really prefer the “hook” solution if it can be worked out, but I tried wrapping a “main” function:

def main():
    x=y  # cause exception as y is undefined

try:
    main()
except:
    console.show()

Running this results in a hard hang of Notepad++!

[Claudia Frank]

@Alan-Kilborn

ok - tried to understand the python script source code and this is what I assume is
what happens.

When executing python files, the one we create with Plugins->PythonScript-New Script
code.py is NOT used, instead the C++ implementation of the python interface,
namely PyRun_Simplefile. Makes a lot of sense.

When executing code in the console then code.py is used. (Not interesting for this issue)

Because of this, there is no need to change code.py but to make a global execption hook
working we have to put the following code into one of the startup.py files.
I prefer user startup.py but machine startup.py will work too.

import sys

def my_logging_func(exctype, value, traceback):
    console.show()
    console.write('{}\n{}\n{}\n'.format(exctype, value, traceback))

sys.excepthook = my_logging_func

Of course the my_logging_func code could look different for each.
But the parameters need to be 3!

When does it fail?
Python interpreter tries to compile the source before it gets executed and that means
if an exception is raised while compiling the source which includes the exception hook,
the hook cannot be installed.

Concerning the console.show() freeze, I’m using the console.show() since I started
with python script. I also tried your example it is working for me.

When your npp hangs than it means that python script created a deadlock.
But what could be the cause when running console.show()?
Can you run console.hide() when you open the console manually (via menu)?
Is there something special in your startup.pys?

Cheers
Claudia

[Claudia Frank]

@Alan-Kilborn

came just into my mind - could it be that you are using callbacks in your
startup.py files which could jump in?

Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

Okay, I disabled code initiated from startup.py that had a callback associated with it, and…everything (the “my_logging_func” stuff, and the “try/main()” stuff) discussed above now works. So the question becomes, what do the callbacks have to do with anything, as long as the callbacks don’t contain any code with unhandled exceptions?

And then the next question is, how do I get it all…my code with callbacks, and a custom exception handler (which does the console.show() )?

And again, Claudia, thank you for your diligence!

[Claudia Frank]

@Alan-Kilborn

Just a quick update - the exception hook should work together with your callbacks,
opening the console is the problem. If you want to know more about this there must
be an old thread at sourceforge forum.
To overcome this, use notepad.runPluginCommand(‘Python Script’, ‘Show Console’)
instead of console.show() (Please double check syntax)

Cheers
Claudia

[Alan Kilborn]

@Claudia-Frank

I found this at sourceforge. It doesn’t really detail anything, but it reminds me of our current discussion!
https://sourceforge.net/p/npppythonscript/discussion/1188885/thread/a1ec71f7/?limit=25#c261

[Alan Kilborn]

So here’s what I ended up embedding in startup.py…seems to do the job and meet the original requirement:

import traceback
def custom_exception_handler_func(exctype, value, trace_back):
    notepad.runPluginCommand('Python Script', 'Show Console')  # can't/don't use console.show()
    sys.stderr.write('(Single-level) Traceback:' + '\n')
    sys.stderr.write(traceback.format_tb(trace_back)[-1])  # only write out ONE level
sys.excepthook = custom_exception_handler_func