fastprogress is a Python library that provides fast and flexible progress bars for both Jupyter Notebook and console environments. Created by Sylvain Gugger for fast.ai, it offers advanced features including nested progress bars, real-time graph plotting, and specialized support for machine learning training loops. The library allows developers to track progress with customizable comments, update graphs dynamically during training, and seamlessly switch between notebook and console displays. It's particularly popular in the machine learning community for visualizing training progress and metrics in real-time.