[Tutor] exception details

[Marilyn Davis]

YES!  Thank you.  That's it.

Also, thank you for the reminder about random.choice!

Whew.

Lovely when things make sense again.

Marilyn

On Thu, 25 Mar 2004, Gregor Lingl wrote:

> 
> 
> Marilyn Davis schrieb:
> 
> >Hi,
> >
> >I'm trying to get a strong handle on exception mechanism details.
> >
> >Note that there are three try/except's and that the 1st 2 work
> >fine.  But the third one doesn't catch the random exception
> >generated.
> >
> >Do I have a typo?
> >
> >Thank you for any help you can give.
> >
> >Marilyn Davis
> >
> >#!/usr/bin/env python2.2
> >'''Ways to get more info about your caught exception.'''
> >
> >import exceptions # to get a list of built-in exceptions
> >...
> >
> 
> >   try:
> >        fun('''catch with "Exception, exception: on random exception doesn't work"''')
> >    except Exception, exception:
> >  
> >
> ########### here Exception has to be an expression that matches an exception
> ########### object that propagates from the try clause
> ########### in your code a string propagates from the try clause
> 
> >        print 'exception.args = ', exception.args
> >        print 'exception = ', exception
> >
> so I converted this string to an exception object
> (maybe there is a better way doing this than using eval)
> and now it works:
> 
> import exceptions # to get a list of built-in exceptions
> import random
> import sys  # gives info -- you can use the traceback module but
>             # it uses sys.
> 
> def ok(msg):
>     raise ValueError, msg
> 
> def fun(msg):
>     '''Raises a random built-in exception.'''
>     excepts = dir(exceptions)[:-2]
>     raise_this = random.choice(excepts) # a string
>     raise_this = eval(raise_this) # an exception object
>     print 'Raising', raise_this, 'To', msg
>     raise raise_this, msg
> 
> if __name__ == '__main__':
>     try:
>         ok('this works ok')
>     except Exception, exception:
>         print 'exception.args = ', exception.args
>         print 'exception = ', exception
>         print
> 
>     try:
>         fun('catch with "except:" on random exception works')
>     except:
>         print 'Caught: sys.exc_type =', sys.exc_type,\
>               'sys.exc_value =', sys.exc_value
>         print 'sys.exc_traceback =', sys.exc_traceback
>         print sys.exc_info()
>         print
> 
>     try:
>         fun('catch with "Exception, exception: on random exception does 
> equally work"')
>     except Exception, exception:
>         print 'exception.args = ', exception.args
>         print 'exception = ', exception
> 
> 
> Hope that gives you a clue (together with Python Docs, Library Reference 
> 2.4)
> Gregor
> 
> 

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