[Tutor] Trapping Interpreter errors as a string

[Remco Gerlich]

On Mon, Feb 26, 2001 at 06:33:36PM -0900, Tim Johnson wrote:
> 	Am looking for a way to trap python errors as a string.
> A quick example would be like the disarm function in the rebol language.
> 
> To be more specific:
> Let's say I had a simple cgi program to first sent the the mime-type
> print "Content-type: text/html\n"
> 
> then I do something dumb, like
> 
> integer = string.atoi("duh")
> 
> Guido will then say:
> 
> Traceback (innermost last):
>   File "<stdin>", line 1, in ?
> ValueError: invalid literal for atoi(): duh
> 
> To reduce this inquiry:
> 1)Can that error message be returned to the user as a string.
> 2)Is there a specific numeric error code attached to the error message.
>    i.e. ValueError = ?
> 
> Then the programmer could gracefully complete the output form with
> the error message within it.

In Python, you would usually make something like this:

try:
   x = string.atoi("duh")
except ValueError, problem:
   print problem
   
This will print "invalid literal for int(): duh" and then continue. You put
whatever code you need to handle the exception in the except: block. You can
look at sys.exc_info for more information on the current exception, or
inspect the traceback and/or print it with functions from the traceback
module.

If you don't know about exceptions yet, read chapter 8 of the Tutorial.

-- 
Remco Gerlich