I use VHDL, not used Python. My understanding is that Python will be many times slower than VHDL, so verification tests that take the best part of a week would then take several weeks with Python. And being dynamically typed is fine if you are running a script that returns quickly, but what about it borking even hours into a simulation, when you can catch most dynamic type errors with stronger typed languages at compile time. Python doesn't look like a compelling replacement for VHDL, unless my understanding is off.