Let’s suppose that you have a system running Ubuntu 16.04, 16.10, or 17.04, and you want Python 3.6 to be the default Python.
If you’re using Ubuntu 16.04 LTS, you’ll need to use a PPA:
sudo add-apt-repository ppa:jonathonf/python-3.6 # (only for 16.04 LTS)
Then, run the following (this works out-of-the-box on 16.10 and 17.04):
sudo apt update
sudo apt install python3.6
sudo apt install python3.6-dev
sudo apt install python3.6-venv
wget https://bootstrap.pypa.io/get-pip.py
sudo python3.6 get-pip.py
sudo ln -s /usr/bin/python3.6 /usr/local/bin/python3
sudo ln -s /usr/local/bin/pip /usr/local/bin/pip3
# Do this only if you want python3 to be the default Python
# instead of python2 (may be dangerous, esp. before 2020):
# sudo ln -s /usr/bin/python3.6 /usr/local/bin/python
When you have completed all of the above, each of the following shell commands should indicate Python 3.6.1 (or a more recent version of Python 3.6):
python --version # (this will reflect your choice, see above)
python3 --version
$(head -1 `which pip` | tail -c +3) --version
$(head -1 `which pip3` | tail -c +3) --version