Python deployments

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Check Python[edit | edit source]

Check the version of the default Python interpreter: python --version

List the versions of python available: ls /usr/bin/python*

Use update-alternatives to setup system-wide ability to choose Python interpreter. The one with the higher priority number will become the default.
update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
update-alternatives --install /usr/bin/python python /usr/bin/python3.6 2

Now we can list the choices: update-alternatives --list python

And choose one: update-alternatives --config python

We can also remove a choice if it's no longer an option on the system: update-alternatives --remove python /usr/bin/python2.7

Python Virtual Environments[edit | edit source]

See Digital Ocean's quick guide to setting up a local Python programming environment, including virtual environments, which is what I did for SoundScrape Btw, SoundScrape is a neat tool to download sound files from SoundCloud. [1]

Hynek Schlawack (from 2013)

Python Packaging[edit | edit source]

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 docs. Also note that venv is the successor to virtualenv

Basic PIP and Virtual Environments[edit | edit source]

Do NOT (normally) use sudo with pip. Use a virtual environment. As of Python 3.4, the command is now called pyvenv or simply venv. As of Python 3.6 pyvenv is deprecated in favor of using python3 -m venv</cod> to help prevent any potential confusion as to which Python interpreter a vritual environment will be based on.

$ python3 -m venv myenv
.. some output ..
$ source myenv/bin/activate
(myenv) $ pip install what-i-want
# done using this python?
deactivate

You only use sudo or elevated permissions when you want to install stuff for the global, system-wide Python installation.

It is best to use a virtual environment which isolates packages for you. That way you can play around without polluting the global python install.

As a bonus, virtualenv does not need elevated permissions.

  • Installing a package is as simple as pip install foo
  • Upgrades are pip install --upgrade foo
  • pip uninstall foo if you want to remove foo

References[edit source]

  1. cd
    mkdir environments
    cd environments/
    pyvenv my_env
    source my_env/bin/activate
    pip install --upgrade pip
    pip install soundscrape
    pip install soundscrape --upgrade
    soundscrape https://soundcloud.com/pianoman_weddings/coldplay