### python3.8インストール
$ sudo apt install -y python3.8
### 入っているpython
$ python -V
Python 2.7.17
$ python3 -V
Python 3.6.9
$ python3.8 -V
Python 3.8.0
$ ll /usr/bin/python*
lrwxrwxrwx 1 root root 9 Apr 16 2018 /usr/bin/python -> python2.7*
lrwxrwxrwx 1 root root 9 Apr 16 2018 /usr/bin/python2 -> python2.7*
-rwxr-xr-x 1 root root 3637096 Apr 15 17:20 /usr/bin/python2.7*
lrwxrwxrwx 1 root root 9 Oct 25 2018 /usr/bin/python3 -> python3.6*
-rwxr-xr-x 1 root root 1018 Oct 28 2017 /usr/bin/python3-jsondiff*
-rwxr-xr-x 1 root root 3661 Oct 28 2017 /usr/bin/python3-jsonpatch*
-rwxr-xr-x 1 root root 1342 May 1 2016 /usr/bin/python3-jsonpointer*
-rwxr-xr-x 1 root root 398 Nov 15 2017 /usr/bin/python3-jsonschema*
-rwxr-xr-x 2 root root 4526456 Apr 18 01:56 /usr/bin/python3.6*
-rwxr-xr-x 2 root root 4526456 Apr 18 01:56 /usr/bin/python3.6m*
-rwxr-xr-x 1 root root 5203488 Oct 28 2019 /usr/bin/python3.8*
lrwxrwxrwx 1 root root 10 Oct 25 2018 /usr/bin/python3m -> python3.6m*
$ cd /usr/bin
$ sudo rm python
$ sudo ln -s python3.8* python
$ python -V
Python 3.8.0
