def read_files(*filenames):
    """
    Output the contents of one or more files to a single concatenated string.
    """
    output = []
    for filename in filenames:
        f = codecs.open(filename, encoding='utf-8')
        try:
            output.append(f.read())
        finally:
            f.close()
    return '\n\n'.join(output)
Output the contents of one or more files to a single concatenated string.