Example

Create a new virtual environment, install virtualenv-activator inside it, and then activate it using the etc/activate.sh script.

$ cd /path/to/my_code
$ virtualenv venv
$ venv/bin/pip install virtualenv-activator
$ . venv/etc/activate.sh
(my_code) $

Deactivate as normal…

(my_code) $ deactivate

Well, it’s not as normal as it looks. There’s some magic happening under the hood. Try setting an environment variable in the etc/environment.sh file (this file doesn’t exist by default) in your virtual environment, but also set the same variable to a different value while you’re outside the virtual environment, and then watch what happens the variable as you activate and deactivate the environment.

$ echo 'export MY_VAR="inside venv"' > venv/etc/environment.sh
$ export MY_VAR="outside venv"
$ echo $MY_VAR
outside venv
$ . venv/etc/activate.sh
(my_code) $ echo $MY_VAR
inside venv
(my_code) $ export MY_VAR="manually set"
(my_code) $ echo $MY_VAR
manually set
(my_code) $ deactivate
$ echo $MY_VAR
outside venv
$ . venv/etc/activate.sh
(my_code) $ echo $MY_VAR
inside venv

Basically, you can put pretty much anything bash related (variables, aliases, functions, etc.) in the etc/environment.sh script and it will only exist when your virtual environment is activated.

NOTE: You may have noticed in the example above that the parent directory’s basename was used in my prompt instead of the basename of the virtual environment directory itself. It does this when you name your virtual environment something generic like venv, in which case it wouldn’t really be very informative to have that in your prompt. It uses this regular expression to decide if the name is “generic”: ^\.?v(irtual)?env$

Simple Mode

Simple mode is enabled via the VIRTUALENV_ACTIVATOR_SIMPLE environment variable. When this variable is set, the activator doesn’t try to restore your environment to its previous state. It doesn’t even provide a deactivate function. This is sometimes more desirable when running a daemon for instance. Here’s an example of a bash script you might write to wrap a daemon written in Python so that the virtual environment is automatically activated for the daemon:

#!/bin/bash
export VIRTUALENV_ACTIVATOR_SIMPLE=1
. /path/to/venv/etc/activate.sh
my_daemon "$@"