Setting an environment variable in virtualenv

Leveraging virtualenvwrapper's superpowers

Set up a long-lasting environment with virtualenvwrapper. It optimizes your workflow with helpful hooks such as postactivate and predeactivate.

Elevate your activation game with hooks

Populate your postactivate script:

echo 'export FOO=foo' >> $VIRTUAL_ENV/bin/postactivate
# Wait, is there a bar for foo here?
echo 'cd /path/to/project/dir' >> $VIRTUAL_ENV/bin/postactivate


This ensures your variable FOO gets a value every time your virtualenv activates, thus providing continuous reinforcement to your workspace.

Clear the environment gracefully with predeactivate:

echo 'unset FOO' >> $VIRTUAL_ENV/bin/predeactivate
# Don't let the FOO loose outside. Clean as you leave!


This ensures not a trace of FOO, preventing your global environment from getting confused about its origin.

Reshuffle directories efficiently

Virtualenvwrapper enables you to create a symlink to your project directory within your virtualenv:

ln -s /path/to/project/dir $VIRTUAL_ENV/project
# Like a wormhole to your project!


This allows quick switching between projects. Less navigation, more action!

Automate environment configuration

Mkvirtualenv from virtualenvwrapper is a power tool to auto-create symlinks, environment variables, and more on the fly:

mkvirtualenv --no-site-packages my_project
# Let the magic begin...


Do it once, replicate it a thousand times.

Alternate routes for seamless integration

Direnv — the environment shape-shifter

Direnv automatically sets environment variables as soon as you enter a directory, like a perfect butler:

echo 'export FOO=foo' > .envrc
direnv allow .
# Your wish is my command, master!


Ever in doubt? Check out direnv's GitHub for elaborate and exhaustive tweaks.

One shot, one kill: activate script modification

Modify the activate script inside bin of your virtualenv to quickly set an environment variable:

echo 'export FOO=foo' >> $VIRTUAL_ENV/bin/activate
# Like tattooing your environment!


But remember, what's tattooed should be erased. Include the corresponding unset command in the deactivate function.

Edge cases and their antidotes

When playing with symlinks or shell integrations, always backup your environment variables. Treat them delicately to prevent chaos:

OLD_JUDGE=$JUDGEMENT
export JUDGEMENT=NewPerception
# A bit of amnesia never hurt!


Then, bring back the old values on deactivation using the predeactivate hook:

echo 'export JUDGEMENT=$OLD_JUDGE' >> $VIRTUAL_ENV/bin/predeactivate
# Time travel back to the old perception.


Soak up the wisdom of documentation

Seize the guidance from official documentation for in-depth understanding and prolific usage.