Ref: how can I create a program with python 3.5
This is a question in Ask Ubuntu about creating a program with python3.5.
The Question was closed as being off-topic.
"Help Center > Asking, What topics can I ask about here? Questions that you may ask: Running third-party applications on Ubuntu."
Python is installed in Ubuntu using: sudo apt-get install python3.5
which would indicate that it is a third party app.