try - except. How to identify errors unknown in advance?

[Chris Kaynor]

On Wed, Nov 16, 2011 at 8:57 AM, Frederic Rentsch
<anthra.norell at bluewin.ch> wrote:
> Hi all,
>
>
> I'd like to log MySQL errors. If I do:
>
>        try: (command)
>        except MySQLdb.OperationalError, e: print e
>
> I may get something like:
>
>        (1136, "Column count doesn't match value count at row 1")
>
> If I don't know in advance which error to expect, but on the contrary
> want to find out which error occurred, I can catch any error by omitting
> the name:
>
>        except: (handle)
>
> But now I don't have access to the error message 'e'. I'm sure there's a
> way and it's probably ridiculously simple.

except Exception, e: (or, in Py3, except Exception as e is prefereed).

Note that you should generally avoid bare except statements "except:"
as that will catch everything, including KeyboardInterrupt and
SystemExit which may not be desirable.

Even without saving the exception in the except statement, you can get
the type, value, and traceback with the sys.exc_info command. See
http://docs.python.org/library/sys.html#sys.exc_info

For example:

py>import sys
py>try:
py> raise RuntimeError
py> except:
py> print sys.exc_info()
py>
(<type 'exceptions.RuntimeError'>, RuntimeError(), <traceback object
at 0x0000000002371588>)

>
> Frederic
>
>
>
> --
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>