Woocommerce get product type

functions.php

/**
 * is_type can be simple, variable, grouped, external
 * woocommerce_single_product_summary is hook!
 * Put this into your functions.php (child-theme)
**/
add_action( 'woocommerce_single_product_summary', 'get_product_type',  5 );
function get_product_type() {
        global $post;
            if( function_exists('get_product') ){
                $product = get_product( $post->ID );
                if( $product->is_type( 'variable' ) ){
                echo // do something with external products
        }
    }
}