In the development environment of Ubuntu, due to many incompatibilities between Python 2 and Python 3, we often need to manually switch between Python versions.
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 100
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150
If you want to switch back to Python 2.7, you can use the command:
sudo update-alternatives --config python
Run Python -- version to view the current version of Python being used.
For example, if you are currently using Python 2:
$ python --version
Python 2.7.17
You can use the following command to switch to Python 3:
$ sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 150
[sudo] password for ts:
update-alternatives: using /usr/bin/python3 to provide /usr/bin/python (python) in auto mode
$ python --version
Python 3.6.9
To switch to Python 2 again, you can use the following command:
$ sudo update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/bin/python3 150 auto mode
1 /usr/bin/python2 100 manual mode
2 /usr/bin/python3 150 manual mode
Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/bin/python2 to provide /usr/bin/python (python) in manual mode
$ python --version
Python 2.7.17