[lifthrasiir]

> 2. Be very careful about tools like pybind11 that make it easier to write extensions for Python. They come with a significant amount of overhead. For critical hotspots, always use the raw Python C extension API.

Agrees on the broader point (and I don't like pybind11 that much anyway), but the raw Python C extension API is often hard to use correctly. I would suggest that you should at least have a rough idea about how higher-level libraries like pybind11 would translate to the C API, so that you can recognize performance pitfalls in advance.

> 3. Use numpy arrays whenever possible when returning large lists to Python. A python list of python integers is amazingly inefficient compared to a numpy array of integers.

Or use the `array` module in the standard library if that matters. numpy is not a small library and has quite a large impact on the initial startup time. (Libraries like PyTorch are even much worse to be fair, though.)