Or "likelihood that program runs correctly if compiles correctly X" is too low, or "ability to write concurrent code in straight-line fashion rather than with callbacks X" is "too low".
When single threaded top-down Python is too slow for a particular task, of late I find it easier/cleaner/faster to use Go routines than multiprocessing / threading in Python, because of the way concurrency was designed in Go, but added to Python.
> "ability to write concurrent code in straight-line fashion rather than with callbacks X"
-or-
If you are looking for X, use X.