Re: Regarding exception handling

From: Dan Perl (danperl_at_rogers.com)
Date: 01/31/05 

Date: Mon, 31 Jan 2005 00:06:23 -0500

"Bryan" <belred@gmail.com> wrote in message
news:mailman.1614.1107137827.22381.python-list@python.org...
> IMO, that is not the reason for the try/finally statement and it is not
> redundant. the try/finally statement guarantees the resource is closed
> and the try/finally statement only gets executed if and only if the
> opening of the resource doesn't raise an exception. it has nothing to do
> with exception handling.

But IMO, try-finally is meant to be used only if the block in the try clause
may raise exceptions. Here is an example that shows what I meant:
    s = ... # socket opens
    try:
        a = 1
    finally:
        s.close()

works perfectly the same as:
    s = ... # socket opens
    a = 1
    s.close()

The try-finally statement does not "handle" the exception, but it makes
sense only if exceptions are possible. There is no point in enclosing "a =
1" in any kind of try statement.

According to a following posting from Angelos he did expect some other
exceptions than socket.error and hence the nested try's. To my defence
though, I put in a disclaimer for that case in my initial posting.

> in the previous 2 examples s = ... was placed inside the try/finally, but
> if an exception occures and s doesn't get bound to an object, then
> s.close() in both examples will raise a NameError on s.

That is a very good point. I missed it.

Dan