sudo apt install python3.8
$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 1
$ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.8 2
$ sudo update-alternatives --config python3
user@ubuntu1804:~$ sudo update-alternatives --config python3
There are 2 choices for the alternative python3 (providing /usr/bin/python3).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/bin/python3.6 1 auto mode
1 /usr/bin/python3.6 1 manual mode
2 /usr/bin/python3.8 2 manual mode
Press <enter> to keep the current choice[*], or type selection number:
注：本文转载于 https://tech.serhatteker.com/post/2019-12/upgrade-python38-on-ubuntu/ ，如有维权，请联系博主删除