You can make web apps with Python. Almost never pure Python is used, a web framework is used to create web apps.
There are many frameworks including: Flask, Django, Bottle, Pyramid and Morepath. The frameworks Flask and Django are the most popular.
Flask is a micro framework, it contains the bare minimum to build web apps. Django is an huge framework that takes a lot of time to setup, but comes with many features like an Object Relational Manager (ORM) and other stuff.