Looping through list of custom post types.

gistfile1.php

<?php $loop = new WP_Query( array( 'post_type' => 'post_type', 'posts_per_page' => 10 ) ); ?>
  <?php while ( $loop->have_posts() ) : $loop->the_post(); ?>
  <article>
    <a href="<?= get_permalink();?>"><h2><?= the_title();?></h2></a>
    <?php the_excerpt(); ?>
  </article>
<?php endwhile; ?>