How to programmatically update short and long description using csv file for magento products ?

<?php
require_once '../app/Mage.php';
umask(0) ;
Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);

$csv = new Varien_File_Csv();
$data = $csv->getData('sku_description.csv'); //path to csv
array_shift($data);

for($i=0;$i<count($data);$i++)
{
if($data[$i][0] != "")
{
$product_sku = $data[$i][0];
$short_description = $data[$i][1];
$long_description = $data[$i][2];

$product = Mage::getModel('catalog/product')->loadByAttribute('sku',$product_sku);

if($product) {
$product->setShortDescription($short_description);
$product->setDescription($long_description);
$product->save();
echo "Updated product " . $productSku . "<br>";
}else
{
echo "Not - Updated product " . $productSku . "<br>";
}
}
}
?>

Please check image for CSV format.