###Magento 1.x code:
Mage::getConfig()->getModuleDir('etc', 'Df_Localization')
###Magento 2 code:
/**
* @param string $moduleName
* @param string $type [optional]
* @return string
* @throws \InvalidArgumentException
*/
function df_module_dir($moduleName, $type = '') {
/** @var \Magento\Framework\ObjectManagerInterface $om */
$om = \Magento\Framework\App\ObjectManager::getInstance();
/** @var \Magento\Framework\Module\Dir\Reader $reader */
$reader = $om->get('Magento\Framework\Module\Dir\Reader');
return $reader->getModuleDir($type, $moduleName);
}