In my day job I've recently been working on visualizing time series data with matplotlib. When I've wanted some sort of specific formatting or behavior, I've had to wade deep in the library documentation to figure out the code for the things I want to do. That's fine, but what frustrates me is that in the back of my mind, I'm pretty sure these are all things I've actually done before. A few years ago in graduate school I took a course that was heavy on matplotlib plotting, and I spent many hours figuring out bizarre techniques for getting very specific results. Unfortunately I've forgotten almost all of that library-specific minutiae.
This has led me to a new project -- I'm creating a personal data science utilities library with modules for matplotlib/seaborn, pandas, geopandas, and scikit-learn, each containing functions that do all the random things I've repeatedly built custom code solutions for in the past. The hope is that I don't need to keep re-learning the same things and can call simple wrapper functions that I've written.