How to Change Default Number of Displayed Posts in WordPress

function wps_number_displayed_posts($query) {
if (is_admin() || !$query->is_main_query()) {
return;
}
if (is_search()) {
$query->set('posts_per_page', 10);
return;
}
}
add_action('pre_get_posts', 'wps_number_displayed_posts', 1);