[Python-Dev] cpython: Rename contextlib.ignored() to contextlib.ignore(). (original) (raw)

Victor Stinner victor.stinner at gmail.com
Wed Oct 16 17:10:21 CEST 2013

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: dosomething() with: with trap(OSError) as cm: os.unlink('missing.txt') some other code if cm.exc is not None: dosomething() 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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