Chris,
I'd rather see a real-world example that can't be solved with either better design or some simple aliases. (And yes, the type hinting does allow for aliases.)
Python is a duck-typing language, Chris. It is in its nature -- and we have been taught -- to ignore types and care only about operators. This means one of the most common design decisions in Python is exactly to code functions that are type ignorant. That is exactly why we need Type Hinting, because duck-typing complicates static analysis. And that is exactly why the Unions factory are a necessary part of the type hinting mechanism in PEP 484.
You will be seeing lots and lots of Unions in type annotated code once it gets implemented. And it's not because of the complexity of Unions syntax that I should now care about refactoring my code. That is a no-no.
If you don't know of any real-life example of python functions that will eventually force you into annotate them with unions syntax, look no further than your standard library. And also start questioning if you aren't complicating your own code with unnecessary function overloads.
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