Re: exception problem

Discussion in 'Python' started by Andrew Berg, Jun 25, 2012.

  1. Andrew Berg

    Andrew Berg Guest

    On 6/25/2012 12:27 AM, Charles Hixson wrote:
    > The documentation section covering the except statement could stand to
    > be a *LOT* clearer. I read the sections on the except statement and
    > exception handlers several times and couldn't figure out was the "as"
    > argument of the except statement was for.

    I agree that the tutorial doesn't explain the use of "as" very well, but
    it does cover that a bare except is not normally good to use:
    "The last except clause may omit the exception name(s), to serve as a
    wildcard. Use this with extreme caution, since it is easy to mask a real
    programming error in this way!"

    > I still don't really know what
    > "as" means, except that if you use it, and you print out the "target",
    > you'll get some kind of informative message.

    "as" lets you refer to the exception object that was caught. I find this
    useful mainly for exceptions that have attributes (most built-in
    exceptions don't, but many user-defined exceptions do). A full traceback
    is much more useful for debugging than what a simple print(exc) will give.
    There are a few different ways to get traceback information without
    letting the exception simply propagate and terminate the program. You
    can get some simple information from sys.exc_info() (and you can feed
    the traceback object to a function in the traceback module), or you can
    log it with the logging.exception() function or the exception() method
    of a Logger from the same module. I recommend using logging. However,
    it's generally best to just let any unexpected exceptions propagate
    unless the program absolutely must continue, especially when debugging.
    --
    CPython 3.3.0a4 | Windows NT 6.1.7601.17803
    Andrew Berg, Jun 25, 2012
    #1
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