Okay, I finally have the explanation of this double installation (see https://docs.python.org/3/using/mac.html)
It must certainly come from a direct installation that I had done since https://www.python.org/ but I did not remember it anymore... I do so many things :-/ It remains to be seen now what is the easiest use in time of Python, via python.org or via Macports ... What do you think ?
