Make and Bash are useful tools but the syntax can be tricky, especially if you’re writing Bash inside a Makefile. And sometimes you need the flexibility and expressivity of a proper programming language with a standard library.
If you know Ruby, you’re probably already familiar with Rake; and for Python there’s Invoke. But maybe you don’t want to invest time in learning a new tool and its idiosyncracies.
Yatte is for when you just want to write a Python script and get back to work.
Note: A promising language-agnostic alternative is just.
The Quickstart describes how to use Yatte.