How can I alter variables sent to a paragraph bundle template within a module?
Drupal 7

I don't know if this will help you directly, but I found this code snippet on DropBucket and it helped me do something similar:

/**
 * Implements hook_preprocess_entity().
 */
function wwvs_slices_preprocess_entity(&amp;$variables) {
  if ($variables['entity_type'] == 'paragraphs_item') {
    $edge = field_get_items('paragraphs_item', $variables['paragraphs_item'], 'field_edge');
    if ($edge &amp;&amp; $edge[0]['value']) {
      $variables['classes_array'][] = 'slice--edge';
    }
  }
}


In my usecase I wanted to augment the paragraph entity with an ID using the url-safe version of the title field used in that paragraph. Here's my implementation:

/**
 * Implements hook_preprocess_entity().
 */
function foo_preprocess_entity(&amp;$variables) {
  if ($variables['entity_type'] == 'paragraphs_item') {
    if(isset($variables['elements']['pp_title']['#items'][0]['value'])){
      $title = $variables['elements']['pp_title']['#items'][0]['value'];
      $title = strtolower(drupal_clean_css_identifier($title));
      $variables['attributes_array']['id'] = $title;
    }
  }
}


I hope this is helpful!