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Wed Oct 16 17:10:21 CEST 2013 · https://mail.python.org/pipermail/python-dev/2013-October/129632.html

I would rewrite your examples using try/finally:

    try:
        try:
            os.unlink('missing.txt')
        finally:
            some
            other
            code
    except OSError as exc:
        do_something()

It's differently than yours, because it catchs OSError on "some; other; code".

Sometimes, I write it differently by copying the cleanup code:

    try:
        os.unlink('missing.txt')
        cleanup()
    except OSError as exc:
        cleanup()
        do_something()

(Yeah, it's ugly to duplicate code.)

Victor

2013/10/15 R. David Murray <rdmurray at bitdance.com>:
> You wouldn't use trap/as for that.  Instead you use it to replace this:
>
>     exc = None
>     try:
>         os.unlink('missing.txt')
>     except OSError as exc:
>         pass
>     some
>     other
>     code
>     if exc is not None:
>         do_something()
>
> with:
>
>     with trap(OSError) as cm:
>         os.unlink('missing.txt')
>     some
>     other
>     code
>     if cm.exc is not None:
>         do_something()
>
> which saves you *three* lines, not just two :)
>
> Of course in real life, in order for 'some other code' really be the
> best way to organize this snippet, you're going to be doing something
> more complicated than catching OSError from an unlink call.
>
> If this is accepted, I do *not* expect to see this in real code very
> often at all.  The main motivation for it is to make the semantics
> of the context manager clearer, and as a bonus make it work like
> assertRaises, which is our existing stdlib context manager that traps
> exceptions.
>
> I'd be happy with 'trap' or 'catch' without 'as' support, but the
> names make more sense if the exception is actually available after
> it is trapped/caught.
>
> --David
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[Python-Dev] cpython: Rename contextlib.ignored() to contextlib.ignore().