I've been using for more than 12 years PHP with Apache (a.k.a mod_php) for my web
development work. I've recenlty discovered python and its real power (I still don't understand why this is not always the best product that becomes the most famous).
I've just discovered mod_python for Apache. I've already googled but without success things like mod_python vs mod_php. I wanted to know the differences between the two mod_php and mod_python in terms of:

speed
productivity
maintainance
(I know `python is most productive and maintainable language in the world, but is it the same for Web programming with Apache)
availability of features e.g, cookies and session handling, databases, protocols, etc.
My understanding is that PHP was designed with Internet/Web in mind, but Python is for a more general purpose.
Now most people are leaving mod_python for mod_wsgi, which is more robust and flexible.
To answer other questions:

speed: python is faster. (PHP is slower than both ruby and python)
productivity: at least the same as php with numerous libraries
maintenance: python is clear and neat
features: more than you need, I would say.

Python was not popular on web because it wasn't focused on web at all. It has too many web frameworks (more frameworks than programming languages), so the community has not been as strong as Ruby on Rails.
Web programming: Apache modules: mod_python vs mod_php