If you understand the internals they're anything but pythonic. Coroutines can be a zero overhead abstraction in the some cases.

For example here is a test that verifies the optimized output for a simple (and misnamed) integer generator compiled at -O2. Notice the arguments to `print` are integer literals. (https://github.com/GorNishanov/clang/blob/Experiments/test/C...)

I'm no python expert, but I suspect C++ optimizes this code better.