Another option is to use plotnine, which is intended to be a ggplot2 clone. It uses matplotlib under the hood, so if something isn't right you can tweak it. That was the main drawback I found with Altair: your declarative code is almost literally dumped to a json file and then rendered by a process external to Python, so good luck tweaking your plot.

https://github.com/has2k1/plotnine