Get post excerpt out of the loop

WordPress excerpt out of the loop.php

<?php
// get excerpt out of the loop
function my_excerpt($post_id) {
	$post = get_post($post_id);
	if ($post->post_excerpt) {
		// excerpt exists, return it
		return apply_filters('the_excerpt', $the_post->post_excerpt);

	} else {
		setup_postdata( $post );
		$excerpt = get_the_excerpt();
		wp_reset_postdata();
		return $excerpt;
	}
}