How far down the stack does it need to be correct? Can a 100% correct Python script be considered correct if there could still be bugs further down the stack? Also what's the context of the software? Much software has pretty safe failure modes, but if it's a medical system for example, knowing level of correctness right down to hardware level may be useful.

I think in that light, most modern software can be built to be robust and easily maintainable rather than correct. Like the difference between building a bridge, where you understand everything in the system, versus building a vehicle engine, where you have multiple dependencies but you still need it to not catastrophically fail should any of them stop being correct (eg: fuel pump fails, engine management detects lower fuel pressure and cuts ignition, saving the engine).