The author conflates generators with generator expressions[1]. He's correct in that generator expressions lazily evaluate and lists don't, but actual generators are a much more powerful construct - they're functions which use the `yield` keyword. They're most frequently used as iterators, but they can also communicate with the outside state via receiving values (`x = yield y`), being explicitly closed with `.close()`, or having an exception raised at the yield point with `.throw()`.

They're so powerful in fact, that asyncio is implemented under the hood with a lot of generator cleverness. You rarely see it, but the `__await__` dunder method which powers `await` is just a synchronous function which returns a generator.

Generator expressions are useful for when there's memory constraints that preclude using a list comprehension, but list comprehensions are actually faster because of cPython's internal optimizations.

[0] https://peps.python.org/pep-0255/ [1] https://peps.python.org/pep-0289/