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?
import importlib.util
if importlib.util.find_spec("numpy") is None:
... # whatever you wanted to do if numpy is missing
lazy import numpySeriously: crash if your dependencies aren't available. There are better ways to do optional dependencies. ImportError ain't it.
I might recommend doing something like importing from something like `numpy.version` (or some other "random" very small utils package) so that the work done on file load is still fairly small.
What would that be for numba?
For example, numba._version only imports standard library stuff so is probably good enough here[0]
It would be nice to have general querying capabilities here, of course. I just think that in practice there's at least a halfway-decent workaround in almost any real situation
[0] https://github.com/numba/numba/blob/main/numba/_version.py
"Oh you don't have optional dependency? Then do X" needs to happen at runtime right?
In my preference order: an explicit CLI option/envvar which requires the optional dep, a flag file on the filesystem, or an ImportError attempt if you absolutely must. Use a stub/trampoline file in the conditionals so that static analyzers and laziness analysis on that file itself still work.
Also, you need something that works for simple one-file scripts, not just a whole package or project.
If you need something for one-off scripts, use https://docs.astral.sh/uv/guides/scripts/.