Close as Many Files/External resourcs as possible in the face of exceptions

GZ zyzhu2000 at gmail.com
Mon Nov 21 00:46:35 EST 2011


Hi,

Here is my situation. A parent object owns a list of files (or other
objects with a close() method). The close() method can sometimes fail
and raise an exception. When the parent object's close() method is
called, it needs to close down as many files it owns as possible, even
if the close() function of some files fail. I also want to re-raise at
least one of the original exceptions so that the outer program can
handle it.

What I come up is something like this, suppose L is a list that holds
all the file objects.

is_closed = set()
try:
    for f in L:
        f.close()
        is_closed.add(f)
except:
    try:
        raise #re-raise immediately, keeping context intact
    finally:
        for f in L: # close the rest of the file objects
            if f not in is_closed:
                 try:
                     f.close()
                 except:
                      pass

It will re-raise the first exception and preserve the context and
close as many other files as possible while ignoring any further
exceptions.

But this looks really awkward. And in the case that two files fail to
close, I am not sure the best strategy is to ignore the second
failure.

What is a better way of handling such situation?

Thanks,
gz




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