Show the user a friendly size. Adapted with larger sizes from http://stackoverflow.com/a/1094933

pretty size

def friendly_size(length):
    """
    Returns *binary* human-friendly size. Goes all the way up to YB.

    >>> friendly_size(0)
    '0 bytes'
    >>> friendly_size(1024)
    '1.0 KB'
    >>> friendly_size(1524)
    '1.5 KB'
    >>> friendly_size(1024**4)
    '1.0 TB'
    >>> friendly_size(1024**4 + (1024**4/3))
    '1.3 TB'
    >>> friendly_size(1024**3*2.5)
    '2.5 GB'
    """
    for unit in ['bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB']:
        if length < 1024.0 or unit == 'YB':
            if unit == 'bytes':
                return "%i %s" % (length, unit)
            else:
                return "%3.1f %s" % (length, unit)
        length /= 1024.0