第一步，增加ppa仓库：
sudo add-apt-repository ppa:jonathonf/python-3.7
第二步更新库
sudo apt-get update
第三步安装库
sudo apt-get install python3.7

安装好了后需要对系统默认python切换：

lrwxrwxrwx 1 root root             26 8月  16  2019 dh_pypy -> ../share/dh-python/dh_pypy
-rwxr-xr-x 1 root root           1056 11月 24  2017 dh_python2
lrwxrwxrwx 1 root root             29 8月  16  2019 dh_python3 -> ../share/dh-python/dh_python3
lrwxrwxrwx 1 root root             23 3月   2  2021 pdb2.7 -> ../lib/python2.7/pdb.py
lrwxrwxrwx 1 root root             23 1月  27  2021 pdb3.5 -> ../lib/python3.5/pdb.py
lrwxrwxrwx 1 root root             23 2月  21  2021 pdb3.7 -> ../lib/python3.7/pdb.py
lrwxrwxrwx 1 root root             31 8月  11  2020 py3versions -> ../share/python3/py3versions.py
lrwxrwxrwx 1 root root             26 8月  16  2019 pybuild -> ../share/dh-python/pybuild
lrwxrwxrwx 1 root root              9 8月  11  2020 python -> python2.7
lrwxrwxrwx 1 root root              9 8月  11  2020 python2 -> python2.7
-rwxr-xr-x 1 root root        3492624 3月   2  2021 python2.7
lrwxrwxrwx 1 root root              9 8月  11  2020 python3 -> python3.5
-rwxr-xr-x 2 root root        4456208 1月  27  2021 python3.5
-rwxr-xr-x 2 root root        4456208 1月  27  2021 python3.5m
-rwxr-xr-x 2 root root        5078728 2月  21  2021 python3.7
-rwxr-xr-x 2 root root        5078728 2月  21  2021 python3.7m
lrwxrwxrwx 1 root root             10 8月  11  2020 python3m -> python3.5m
lrwxrwxrwx 1 root root             29 8月  11  2020 pyversions -> ../share/python/pyversions.py

删除python这个软引用：

sudo rm python

创建3.7的软引用

sudo ln -s python3.7 python
变成如下：

lrwxrwxrwx 1 root root             26 8月  16  2019 dh_pypy -> ../share/dh-python/dh_pypy
-rwxr-xr-x 1 root root           1056 11月 24  2017 dh_python2
lrwxrwxrwx 1 root root             29 8月  16  2019 dh_python3 -> ../share/dh-python/dh_python3
lrwxrwxrwx 1 root root             23 3月   2  2021 pdb2.7 -> ../lib/python2.7/pdb.py
lrwxrwxrwx 1 root root             23 1月  27  2021 pdb3.5 -> ../lib/python3.5/pdb.py
lrwxrwxrwx 1 root root             23 2月  21  2021 pdb3.7 -> ../lib/python3.7/pdb.py
lrwxrwxrwx 1 root root             31 8月  11  2020 py3versions -> ../share/python3/py3versions.py
lrwxrwxrwx 1 root root             26 8月  16  2019 pybuild -> ../share/dh-python/pybuild
lrwxrwxrwx 1 root root              9 11月  4 23:49 python -> python3.7
lrwxrwxrwx 1 root root              9 8月  11  2020 python2 -> python2.7
-rwxr-xr-x 1 root root        3492624 3月   2  2021 python2.7
lrwxrwxrwx 1 root root              9 8月  11  2020 python3 -> python3.5
-rwxr-xr-x 2 root root        4456208 1月  27  2021 python3.5
-rwxr-xr-x 2 root root        4456208 1月  27  2021 python3.5m
-rwxr-xr-x 2 root root        5078728 2月  21  2021 python3.7
-rwxr-xr-x 2 root root        5078728 2月  21  2021 python3.7m
lrwxrwxrwx 1 root root             10 8月  11  2020 python3m -> python3.5m
lrwxrwxrwx 1 root root             29 8月  11  2020 pyversions -> ../share/python/pyversions.py