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Tue Oct 15 21:59:55 CEST 2013 · https://mail.python.org/pipermail/python-dev/2013-October/129612.html

On 16 October 2013 05:17, Alexander Belopolsky <
alexander.belopolsky at gmail.com> wrote:

> On Tue, Oct 15, 2013 at 12:45 PM, Ethan Furman <ethan at stoneleaf.us> wrote:
> >     with trap(OSError) as cm:
> >         os.unlink('missing.txt')
> >     if cm.exc:
> >         do_something()
>
> .. and why is this better than
>
> try:
>    os.unlink('missing.txt')
> except OSError as exc:
>    do_something()

It would allow you to perform a series of operations then process the any
exceptions all together e.g.

with trap(OSError) as cm1:
    os.unlink('missing.txt')

with trap(OSError) as cm2:
    os.unlink('other_missing.txt')

with trap(OSError) as cm3:
    os.unlink('another_missing.txt')

for cm in (cm1, cm2, cm3):
    if cm.exc:
        do_something(cm.exc)

An equivalent implementation would be:

exceptions = []

try:
    os.unlink('missing.txt')
except OSError as exc:
    exceptions.append(exc)

try:
    os.unlink('missing.txt')
except OSError as exc:
    exceptions.append(exc)

try:
    os.unlink('missing.txt')
except OSError as exc:
    exceptions.append(exc)

for exc in exceptions:
    if exc:
        do_something(exc)

Tim Delaney
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[Python-Dev] cpython: Rename contextlib.ignored() to contextlib.ignore().