def bytes_conversion(file_path):
    """
    计算文件大小
    :param file_path: 文件路径
    :return: 文件大小
    """
    number = os.path.getsize(file_path)
    symbols = ('K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y')
    prefix = dict()
    for a, s in enumerate(symbols):
        prefix[s] = 1 << (a + 1) * 10
    for s in reversed(symbols):
        if int(number) >= prefix[s]:
            value = float(number) / prefix[s]
            return '%.2f%s' % (value, s)
    return ".%sB" % number