what programming language to learn other than python in real mass-production product?

[Kai]

I am wondering what is the main programming language for mass-production physical product. Many people (for only those I know) was saying C++ is the choice, as many PCB use C++. is there still other popular PCB designed for using python in real physical product? is the performance slower than other languages? What about if the product itself has features like IOT and deep learning? Are those PCB still using C++ for those application? If python can be a choice for this, when it come to design a PCB, what kind of specification I should be aware of. Thank reading my post.