ls -l /usr/bin/python*

# Output:
/usr/bin/python -> /etc/alternatives/python
/usr/bin/python2 -> python2.7
/usr/bin/python2.7
/usr/bin/python2.7-config -> x86_64-linux-gnu-python2.7-config
/usr/bin/python2-config -> python2.7-config
/usr/bin/python3 -> python3.6
/usr/bin/python3.5
/usr/bin/python3.5-config -> x86_64-linux-gnu-python3.5-config
/usr/bin/python3.5m
/usr/bin/python3.5m-config -> x86_64-linux-gnu-python3.5m-config
/usr/bin/python3.6
/usr/bin/python3.6m
/usr/bin/python3-config -> python3.5-config
/usr/bin/python3m -> python3.5m
/usr/bin/python3m-config -> python3.5m-config
/usr/bin/python-config -> python2.7-config

sudo ln -s python3.6 python3

sudo update-alternatives --config python

# My output in this case:
[sudo] password for m93:
There are 3 choices for the alternative python (providing /usr/bin/python).

Selection    Path                Priority   Status
------------------------------------------------------------
0            /usr/bin/python3.6   2         auto mode
1*           /usr/bin/python2.7   1         manual mode
2            /usr/bin/python3.5   1         manual mode
3            /usr/bin/python3.6   2         manual mode