Just like the title, I want to tell you , don't update python on Ubuntu by ,yourself.
But you can update it by "apt-get update" or "apt-get upgrade".
I've struggled for over 30 hours to make my python work, but I failed and just rebuild my system a few minutes ago. I didn't know why it didn't work well when it been updated.
The fellows are what I did(including the reason and result).