Format the value like a 'human-readable' file size (i.e. 13 kB,
    4.1 MB, 102 Bytes, etc).  Per default decimal prefixes are used (Mega,
    Giga, etc.), if the second parameter is set to `True` the binary
    prefixes are used (Mebi, Gibi).

def do_filesizeformat(value, binary=False):
    """Format the value like a 'human-readable' file size (i.e. 13 kB,
    4.1 MB, 102 Bytes, etc).  Per default decimal prefixes are used (Mega,
    Giga, etc.), if the second parameter is set to `True` the binary
    prefixes are used (Mebi, Gibi).
    """
    bytes = float(value)
    base = binary and 1024 or 1000
    prefixes = [
        (binary and 'KiB' or 'kB'),
        (binary and 'MiB' or 'MB'),
        (binary and 'GiB' or 'GB'),
        (binary and 'TiB' or 'TB'),
        (binary and 'PiB' or 'PB'),
        (binary and 'EiB' or 'EB'),
        (binary and 'ZiB' or 'ZB'),
        (binary and 'YiB' or 'YB')
    ]
    if bytes == 1:
        return '1 Byte'
    elif bytes < base:
        return '%d Bytes' % bytes
    else:
        for i, prefix in enumerate(prefixes):
            unit = base ** (i + 2)
            if bytes < unit:
                return '%.1f %s' % ((base * bytes / unit), prefix)
        return '%.1f %s' % ((base * bytes / unit), prefix)