Python has a significant number of web frameworks outside the usual Django, Flask, Pyramid and Bottle suspects.
TurboGears, born as a full stack layer on top of Pylons, is now a standalone web framework that can act both as a full stack library (like Django) or as a micro framework.
Falcon is a minimalist web framework designed with web application speed as a top priority.
web.py is a Python web framework designed for simplicity in building web applications.
Web2py is a batteries-included philosophy framework with project structure based on model-view-controller patterns.
CherryPy is billed as a minimalist web framework, from the perspective of the amount of code needed to write a web application using the framework. The project has a long history and made a major transition between the second and third release.
Muffin is a web framework built on top of the asyncio module in the Python 3.4+ standard library. Muffin takes inspiration from Flask with URL routes defined as decorators upon view functions. The Peewee ORM is used instead of the more common SQLAlchemy ORM.
This roundup of 14 minimal Python frameworks contains both familiar and less known Python libraries.
The web micro-framework battle presentation goes over Bottle, Flask, and many other lesser known Python web frameworks.
A Python newcomer asked the Python Subreddit to explain the differences between numerous Python web frameworks and received some interesting responses from other users.
Read through the web frameworks listed above and check out their project websites.
It's useful to know what other web frameworks exist besides Django and Flask. However, when you're just starting to learn to program there are significantly more tutorials and resources for Django and Flask on the web. My recommendation is to start with one of those two frameworks then expand your knowledge from there.