>fight with Python and PHP on their markets?

PHP has lots of opensource web-apps: OpenX, Wordpress, Joomla, Drupal, phpBB, SugarCRM, Magento eCommerce, MediaWiki you can just download and run on any hosting in couple of minutes. Every app has a community behind it. Haven't heard about anything as popular built with Rails(except Redmine).

Python - studied in Universities like MIT and can be found in any UNIX/Linux distribution. Lots of bindings and libraries(SciPy, NumPy, Twisted). Ruby bindings and libraries are far behind.