How to add element after every post in the loop, but not the last one

I have a pretty common loop:

global $wp_query, $wpdb;
if ( have_posts() )
{
    while ( have_posts() )
    {
        the_post();

        get_template_part(
             'template_parts/content'
            ,get_post_format()
        );
    }
}
else
{
    get_template_part( 'no_results' );
}

Now I need to add (for example) a <hr /> after each single post, but not the last one.

How would I determine if I currently got the second to last post in the current loop?

Note: This should work for paged loops as well.

another possibility:

if( $wp_query->current_post < $wp_query->post_count-1 ) echo '<hr />';