== Check Python ==
Check the version of the default Python interpreter:
<code>python --version</code>
List the versions of python available:
<code>ls /usr/bin/python*</code>
Use <code>update-alternatives</code> to setup system-wide ability to choose Python interpreter. The one with the '''higher''' priority number will become the default.<br>
<code>update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1</code><br>
<code>update-alternatives --install /usr/bin/python python /usr/bin/python3.6 2</code>
Now we can list the choices:
<code>update-alternatives --list python</code>
And choose one:
<code>update-alternatives --config python</code>
We can also remove a choice if it's no longer an option on the system:
<code>update-alternatives --remove python /usr/bin/python2.7</code>
== Python Virtual Environments ==
See Digital Ocean's quick guide to [https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-local-programming-environment-on-ubuntu-16-04 setting up a local Python programming environment], including [https://virtualenv.pypa.io/en/stable/ virtual environments], which is what I did for [https://github.com/Miserlou/SoundScrape SoundScrape] Btw, SoundScrape is a neat tool to download sound files from SoundCloud.
<ref>
In the old days (2015) there were still debates about how to package Python and install stuff. Now, it's settled. Use pip. Easy_install is dead. See the [https://docs.python.org/3/installing/index.html docs]. Also note that <code>venv</code> is the successor to <code>virtualenv</code>
== Basic PIP and Virtual Environments ==Do NOT (normally) use sudo with pip. Use a virtual environment:. As of Python 3.4, the command is now called <code>pyvenv</code> or simply <code>venv</code>. As of Python 3.6 <code>pyvenv</code> is '''deprecated''' in favor of using <code>python3 -m venv</cod> to help prevent any potential confusion as to which Python interpreter a vritual environment will be based on.
<source lang="bash">
$ virtualenv python3 -m venv myenv
.. some output ..
$ source myenv/bin/activate
(myenv) $ pip install what-i-want
# done using this python?
deactivate
</source>
You only use sudo or elevated permissions when you want to install stuff for the global, system-wide Python installation.
