ArunRocks

Making Python Scripts Show Windows-friendly Errors/Stacktrace

Arun bhai | Wed, Jun 20, 2007

Most of us love to distribute our python programs to others once you have finished coding a neat little script. For Windows users we package it using Py2exe or cx_freeze. However, many of the end-users will not be happy with a black command window popping up, say, when an error is thrown.

Of course the alternative is to write a full blown GUI application using WXPython or PyFLTK. Even the latter, though quite lightweight, adds several megabytes to the distribution, when all you need is a simple message-box indicating an error or showing some informational text. Clearly, its an overkill for your throwaway python scripts.

This is the kind of problem I typically face and I have found a good solution. The answer is ctypes library which comes as a part of the standard distribution from Python 2.5 onwards. It simply calls the messagebox function from user32.dll (which is always present in a windows installation). With the main problem solved, what remained was to obtain the error text and stack trace.

Let’s see how the code looks like:

# Importing all the works for a native Win32 Message Box        
    from ctypes import c_int, WINFUNCTYPE, windll
    from ctypes.wintypes import HWND, LPCSTR, UINT
    prototype = WINFUNCTYPE(c_int, HWND, LPCSTR, LPCSTR, UINT)
    paramflags = (1, "hwnd", 0), (1, "text", "Hi"), (1, "caption", None), (1, "flags", 0)
    MessageBox = prototype(("MessageBoxA", windll.user32), paramflags)

# For printing the stack
    import sys
    import traceback
    from time import sleep

def show_popup(text):
        print text
        MessageBox(text=text, caption="Sample App Says...")

def mainloop():
        raise "Uff!"
        
    if __name__ == '__main__':
        try:
            mainloop()
        except:
            type, value, sys.last_traceback = sys.exc_info()
            lines = traceback.format_exception(type, value,sys.last_traceback)
            show_popup("Aiyooooo..... there has been an error!\n" + 
                "Exception in user code:\n" +
                "".join(lines) +
                "===== Please mail a screenshot to arunvr@gmail.com ===="
                )
        finally:
            sleep(1) # show the console output for a second so that users can read it

EDIT: This is how it looks like in PyMail, one of my scripts-that-grew-into-an-app

Screenshot of a Python Stacktrace in a Messagebox

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Categories: General, Python, Technical, py2exe
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Yet Another Year To Rock Away*

Arun bhai | Wed, Jun 13, 2007

This year’s birthday was yet again celebrated in the best place I could possibly think to celebrate - Mangalore. Once again they have written a truly wonderful writeup about me. Check it out…

Arun Ravindran

Hmmm..so, the dude in the pic is celebrating his birthday.does he need a formal introduction from us or what??!!! If ever there was one guy about whom it was hard to find a description in just one word, then it is Arun Ravindran.call him a gadget freak, regular blogger, an ardent music lover, photographer, pencil drawing enthusiast, flash programmer..and he will answer to all of your calls!! Because, he is no ordinary person, for him being extraordinary is just another day!!

He was one of the active participants in this year’s Ittesbin Skit from ES. Didn’t get to see him onstage? That’s because he was busy back stage giving voice. And don’t think that his voice talent was limited to just one character; more than one role in the ES skit was backed up by his voice!!

Don’t just think that he is good at the extracurricular stuff; he is one of the back bones of his project team. He had joined Infosys in May 2004 as an A.CON in ES (EAI). After working for the UBS and BP at onsite, he came to GAPEAIR2 project and to Mangalore.

He is one witty person who always likes to see the smile on other people’s face. He is also an avid reader and he constantly updates his blog. Maybe because he is also interested in drawing, all his “sweets at my deskFCFS” mails are associated with maps showing the easiest route to his cubicle!!!

Word has leaked out to the smilES team that he has to keep at least two parties in the food court (excluding all the other parties outside) so as to make all his friends happy, such is his popularity in this Minfy!!

Lets all wish this talented dude a very happy birthday!!

Check out these snaps too