"Structural pattern matching" for Python, part 1

I'd love to have this in Python.

One thought: we have pattern matching in Rust, and it's incredibly helpful. The whole "matching a declared constant" thing is a problem in Rust, too, and even though Rust constants are declared in advance and statically typed, it's *still* a potential source of ambiguity; we've wished several times that there was a dedicated syntax to avoid the ambiguity.