def construct_identifier(*args, username_prefix='@'):
    """ Create a post identifier from comment/post object or arguments. 
    
    Examples:
        
        :: 
        
            construct_identifier('username', 'permlink')
            construct_identifier({'author': 'username', 'permlink': 'permlink'})
    """
    if len(args) == 1:
        op = args[0]
        author, permlink = op['author'], op['permlink']
    elif len(args) == 2:
        author, permlink = args
    else:
        raise ValueError('construct_identifier() received unparsable arguments'
            )
    fields = dict(prefix=username_prefix, author=author, permlink=permlink)
    return '{prefix}{author}/{permlink}'.format(**fields)
