This might speed up the py impl a few %

  --- a/py/src/cpu.py
  +++ b/py/src/cpu.py
  @@ -260,7 +260,6 @@ class CPU:
               param = None
               cmd_str = cmd.name
               self.PC += 1
  -        self._debug_str = f"[{self.PC:04X}({ins:02X})]: {cmd_str}"