setting an environment variable in virtualenv

Question

I have a Heroku project that uses environment variables to get its configuration, but I use virtualenv to test my app locally first.

Is there a way to set the environment variables defined on the remote machine inside virtualenv?

Answer 1

In case you're using virtualenvwrapper (I highly recommend doing so), you can define different hooks (preactivate, postactivate, predeactivate, postdeactivate) using the scripts with the same names in $VIRTUAL_ENV/bin/. You need the postactivate hook.

$ workon myvenv  $ cat $VIRTUAL_ENV/bin/postactivate #!/bin/bash # This hook is run after this virtualenv is activated. export DJANGO_DEBUG=True export S3_KEY=mykey export S3_SECRET=mysecret  $ echo $DJANGO_DEBUG True 

If you want to keep this configuration in your project directory, simply create a symlink from your project directory to $VIRTUAL_ENV/bin/postactivate.

$ rm $VIRTUAL_ENV/bin/postactivate $ ln -s .env/postactivate $VIRTUAL_ENV/bin/postactivate 

You could even automate the creation of the symlinks each time you use mkvirtualenv.

Cleaning up on deactivate

Remember that this wont clean up after itself. When you deactivate the virtualenv, the environment variable will persist. To clean up symmetrically you can add to $VIRTUAL_ENV/bin/predeactivate.

$ cat $VIRTUAL_ENV/bin/predeactivate #!/bin/bash # This hook is run before this virtualenv is deactivated. unset DJANGO_DEBUG  $ deactivate  $ echo $DJANGO_DEBUG 

Remember that if using this for environment variables that might already be set in your environment then the unset will result in them being completely unset on leaving the virtualenv. So if that is at all probable you could record the previous value somewhere temporary then read it back in on deactivate.

Setup:

$ cat $VIRTUAL_ENV/bin/postactivate #!/bin/bash # This hook is run after this virtualenv is activated. if [[ -n $SOME_VAR ]] then     export SOME_VAR_BACKUP=$SOME_VAR fi export SOME_VAR=apple  $ cat $VIRTUAL_ENV/bin/predeactivate #!/bin/bash # This hook is run before this virtualenv is deactivated. if [[ -n $SOME_VAR_BACKUP ]] then     export SOME_VAR=$SOME_VAR_BACKUP     unset SOME_VAR_BACKUP else     unset SOME_VAR fi 

Test:

$ echo $SOME_VAR banana  $ workon myenv  $ echo $SOME_VAR apple  $ deactivate  $ echo $SOME_VAR banana 

Answer 2

Update

As of 17th May 2017 the README of autoenv states that direnv is probably the better option and implies autoenv is no longer maintained.

Old answer

I wrote autoenv to do exactly this:

https://github.com/kennethreitz/autoenv