Python Virtual Environments

The usual tools for creating Python virtual environments—venv, virtualenv, pew—don’t play well with xonsh. We won’t dig deeper into why it is so, but the general gist is that these tools are hacky and hard-coded for bash, zsh, and other mainstream shells.

Luckily, xonsh has its own virtual environments manager called Vox. Run to install Vox:

$ xpip install xontrib-vox

Vox

First, load the vox xontrib:

@ xontrib load vox

To create a new environment with vox, run vox new <envname>:

@ vox new myenv
Creating environment...
Environment "myenv" created. Activate it with "vox activate myenv".

The interpreter vox uses to create a virtualenv is configured via the $VOX_DEFAULT_INTERPRETER environment variable.

You may also set the interpreter used to create the virtual environment by passing it explicitly to vox new i.e.:

@ vox new python2-env -p /usr/local/bin/python2

Under the hood, vox uses Python 3’s venv module to create Python 3 virtualenvs. [this is the default]

If a Python 2 interpreter is chosen, it will use the Python 2 interpreter’s virtualenv module.

By default, environments are stored in ~/.virtualenvs, but you can override it by setting the $VIRTUALENV_HOME environment variable.

To see all existing environments, run vox list:

@ vox list
Available environments:
    eggs
    myenv
    spam

To activate an environment, run vox activate <envname>:

@ vox activate myenv
Activated "myenv".

Instead of activate, you can call workon or enter.

If you want to activate an environment which is stored somewhere else (maybe because it was created by another tool) you can pass to vox activate a path to a virtual environment:

@ vox activate /home/user/myenv
Activated "/home/user/myenv".

To exit the currently active environment, run vox deactivate or vox exit:

@ vox deactivate
Deactivated "myenv".

To remove an environment, run vox remove <envname>:

@ vox remove myenv
Environment "myenv" removed.

Instead of remove, you can call rm, delete, or del.

To see all available commands, run vox help, vox --help, or vox -h:

Vox is a virtual environment manager for xonsh.

Available commands:
    vox new <env>
        Create new virtual environment in $VIRTUALENV_HOME

    vox activate (workon, enter) <env>
        Activate virtual environment

    vox deactivate (exit)
        Deactivate current virtual environment

    vox list (ls)
        List environments available in $VIRTUALENV_HOME

    vox remove (rm, delete, del) <env> <env2> ...
        Remove virtual environments

    vox help (-h, --help)
        Show help

virtualenv like prompt

Although it’s included in the default prompt, you can customize your prompt to automatically update in the same way as virtualenv.

Simply add the '{env_name}' variable to your $PROMPT:

$PROMPT = '{env_name: {}}' + restofmyprompt

Note that you do not need to load the vox xontrib for this to work. For more details see Customizing the Prompt.

Automatically Switching Environments

Automatic environment switching based on the current directory is managed with the autovox xontrib (xontrib load autovox). Third-party xontribs may register various policies for use with autovox. Pick and choose xontribs that implement policies that match your work style.

Implementing policies is easy! Just register with the autovox_policy event and return a Path if there is a matching venv. For example, this policy implements handling if there is a .venv directory in the project:

@events.autovox_policy
def dotvenv_policy(path, **_):
    venv = path / '.venv'
    if venv.exists():
        return venv

Note that you should only return if there is an environment for this directory exactly. Scanning parent directories is managed by autovox. You should also make the policy check relatively cheap. (Local IO is ok, but probably shouldn’t call out to network services.)