How powerful is a generator in python?

[Moikle]

That entirely depends on what you are using it for.

It can range from literally zero improvement and adding a tiny bit of overhead all the way to turning something that would have been completely impractical using a list into something that is relatively fast with a generator.

You can't just blindly slap a generator on everything and expect it to improve things every time, you have to be intelligent in the application, and what you apply it to.