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

Raymond Hettinger raymond.hettinger at gmail.com
Sun Oct 13 03:50:51 CEST 2013

On Oct 12, 2013, at 4:30 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

When you ask someone to describe what "try: f() except SomeException: pass" does, they will say that it ignores the exception. And they would be right in that case. FWIW, I presented this to 2500+ people in the keynote at the 2013 U.S. Pycon and have received favorable feedback. Were you only displaying the same short form above?

Yes. The specific example given was:

with ignore(OSError):
     os.remove(somefile)

The intended use for the context manager is for the common cases like these:

try:
        os.mkdir(dirname)
    except OSError:
        pass

def discard(self, key):
     """If the keyed message exists, remove it."""
    try:
        self.remove(key)
    except KeyError:
        pass

Most cases of try/except/pass that I see span only one or two lines in the try-block.

Or did you show some with many lines of code inside the with block? If you didn't, is that because it's a bad idea?

Compare: try: f() g() h() except SomeException: pass

Yes, that is usually a bad idea.
We don't recommend code like that with try/except. Using a context manager in this case wouldn't make it better.

For the record, I am no longer opposed to this context manager, only to its name.

It just like the old days where there were 100+ emails suggesting other names for enumerate() before agreeing that it had been right to begin with.

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