You didn't say why you want to replace/complement Python, but should you want to build web backends, Go is the obvious choice. Decent performance, relative ease

You didn't say why you want to replace/complement Python, but should you want to build web backends, Go is the obvious choice. Decent performance, relative ease of use, good GC, rich standard lib for the task, large third-party support and here to stay. I like Nim too, but it needs more adoption.