Working to Make Python Lazy

This feature seems really valuable for commandline tools! However this paragraph gave me pause:

> Currently, disabling lazy imports disabled the syntax keyword, which means that you can’t use it for circular imports, type checking, etc.

Imo this is a good thing, laziness shouldn't be semantically important. The ability to force disable laziness while maintaining semantics is important for linting and testing, and more often than not, circular imports are a sign of bad code structure.

I've got my reservations about lazy imports, but scipy in particular is such a memory hog, I've increasingly been vendoring smaller utilities out of it. Good lazy imports would be a big help.

> This pattern, for example, can’t be lazy: try: import numpy; except ModuleNotFoundError: ...

Wait, that seems bad. These kinds of modules (especially numba) are often exactly the ones that you want to delay importing. Why not provide a way to check the existence at import time? How are you supposed to handle nonexistence in that case?