I think that the fact that Nick got the code to close multiple files wrong underlines that it is difficult to get right currently.  Nick's code

    try:
        files = [open(fname) for fname in names]
        # ...
    finally:
        for f in files:
            f.close()

only closes the files if all of them were opened successfully.  Moreover, `file.close()` can fail for various reasons, which would result in all remaining files being left open.  When we fix both problems, the code becomes

    try:
        files = []
        for fname in names:
            files.append(open(fname))
        # ...
    finally:
        for f in files:
            try:
                f.close()
            except IOError:
                pass

I think everyone will agree that the version using 'CleanupManager' is nicer.  To be fair, we should note that the need to open many files simultaneously is not very common -- usually, we can make to with opening the files one by one.