Get postcode and country_id from object mage 2

I get all data from checkout, with the next code:

$objectManager = MagentoFrameworkAppObjectManager::getInstance();
            $cart = $objectManager->get('MagentoCheckoutModelCart');
            $shippingAddress = $cart->getQuote()->getShippingAddress();
            $perri = $shippingAddress->getData();

But i want to get only postcode and country_id from my object, if i use the next code, i can get the specific element:

$perri = $shippingAddress->getData('postcode');

If i use the next code, the log show an error:

$perri = $shippingAddress->getData('postcode');
 $perri = $shippingAddress->getData('country_id');

How can i get both items?