Why is Python used on aircraft although it may not be certifiable? I recently had a discussion with people who were active in the aviation industry and told me that one of the main languages/tools they use is Python.

On the other hand I have always known that people avoid C++ or eg Linux due to certification reasons for avionics. Certification is also one of the reasons you don't see AI and computer vision in C++ on aircraft. Yet, those people use Python all the time.

I didn't have (and never will have) the opportunity to ask why and for what they used it. Could someone explain why and for what people would still use Python although it may be very difficult to get it certified?
Just because aviation developers use Python, does not mean that Python actually goes flying.

Lots of aviation development is about testing, stressing, validating, analyzing, and documenting the code that does go flying.   

Python is an excellent language for all that validation work, even though it stays on the ground.