On 06/24/2012 11:23 PM, Andrew Berg wrote:
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.
I read that that would happen, but " print (sys.exc_info()[:2]) "
didn't even yield a blank line. It must have executed, because the
print statement on the line before it executed, and there wasn't a loop
or a jump (and also execution continued "normally" [the code still has
bugs] afterward even if the finally isn't included).
--
Charles Hixson
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