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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_default_tempdir():
 """Calculate the default directory to use for temporary files. This routine should be called exactly once. We determine whether or not a candidate temp dir is usable by trying to create and write to a file in that directory. If this is successful, the test file is deleted. To prevent denial of service, the name of the test file must be randomized."""


    namer = _RandomNameSequence()
    dirlist = _candidate_tempdir_list()

    for dir in dirlist:
        if dir != _os.curdir:
            dir = _os.path.abspath(dir)
        # Try only a few names per directory.
        for seq in range(100):
            name = next(namer)
            filename = _os.path.join(dir, name)
            try:
                fd = _os.open(filename, _bin_openflags, 0o600)
                try:
                    try:
                        with _io.open(fd, 'wb', closefd=False) as fp:
                            fp.write(b'blat')
                    finally:
                        _os.close(fd)
                finally:
                    _os.unlink(filename)
                return dir
            except FileExistsError:
                pass
            except OSError:
                break   # no point trying more names in this directory
    raise FileNotFoundError(_errno.ENOENT,
                            "No usable temporary directory found in %s" %
                            dirlist)