Which language should i choose?

  c++, python, user-interface

I want to write a program for different notebooks (different OS, at least Win, Linux, MacOs) where the user can control through a GUI a fan control. The fan should be regulated by a COM interface. The fan should run safely a long time. I wonder if I should use C++ or Python for this.
Can anybody give me a tip?
I think Python would be better because I can run it easily on all operating systems. But is a GUI written with Python safe enough?

Thank you in advance.

Source: Windows Questions C++