// anywhere in the theme's content-single-product.php
$poids_prix = array();
if ($product->is_type('variable'))
	foreach($product->get_available_variations() as $key=>$variation)
		if ($variation['attributes'] and $variation['attributes']['attribute_poids'] and $variation['weight'])
			$poids_prix[$variation['attributes']['attribute_poids']] = array('poids_kg'=>$variation['weight']*1,'prix_eur'=>$variation['display_price']*1);
echo json_encode($poids_prix);