Population Density in Census Tracts

I am quite new to Python and I am attempting to practice by making a simple program with ArcGIS. I wanted to make a script that automated the calculation of population density of selected census tracts within the city I live in. I also wanted to give the ability for the user to choose the census tract.

I then wanted to provide a map layout in ArcMap of the specific tract with the population, area, and population density being shown.

I realize most of this can be done using ModelBuilder, but I needed practice with Python and thought this would be a good simple program to start with. Anyone have any pointers on the script and also how I could possibly make it better?

Thanks