On embedded systems where system Python is used, to persistently switch default Python version, use
For example, to switch Python default between Python 3 and 2.7 (useful for Raspberry Pi on Raspbian 9.1)
update-alternatives --install /usr/bin/python python /usr/bin/python3 20 update-alternatives --install /usr/bin/python python /usr/bin/python2 10
Then at any time, select the default Python version with
update-alternatives --config python
You might expect something like
--slave /usr/bin/pip pip /usr/bin/pip2 to be part of the
pip is a script with the shebang
#!/usr/bin/python that is already affected by
update-alternatives --config python.
Therefore, we do NOT use
--slave with Python
Fix Ubuntu 17.04 apt install
Ubuntu 17.04 was giving errors on
apt install or
apt upgrade any program.
The syntax errors were due to Python 3 being the default in Ubuntu 17.04, even though I had already installed Python 2.
I fixed this issue by using
update-alternatives with Python 2.7 as above.