Rebuilding a Virtualenv

If you need to rebuild your virtualenv following a system image upgrade

The instructions below will contain instructions for people who use plain virtualenv and virtualenvwrapper; make sure that you use the appropriate ones for the kind of virtualenv you're using. Use a Bash console to enter the commands.

1) Use a requirements.txt file to record what packages you're using

If you've already got a requirements.txt file, you can skip this bit, although you may want to just do the bit where we double-check what version of Python we're using.

  1. Activate your virtualenv, using source /home/myusername/path/to/virtualenv/bin/activate or, if you're using virtualenvwrapper workon my-virtualenv-name
  2. Save the list of packages to a requirements file
    • pip freeze > /tmp/requirements.txt
  3. Double-check which version of python is in your virtualenv
    • python --version
  4. Deactivate the virtualenv
    • deactivate

2) Remove your old virtualenv

Using plain virtualenvs:

rm -rf /home/myusername/path/to/virtualenv

or, if using virtualenvwrapper:

rmvirtualenv my-virtualenv-name

3) Create a new virtualenv

Using the appropriate Python version in place of X.Y:

virtualenv --python=pythonX.Y /home/myusername/path/to/virtualenv

or, with virtualenvwrappper

mkvirtualenv --python=pythonX.Y my-virtualenv-name

4) Reinstall your packages

pip install -r /tmp/requirements.txt  # or path to your existing requirements.txt

5) Restart your web app.

On the Web tab, use the "Reload" button to restart your website code using the new virtualenvs -- don't forget to do this for all of your websites if you have several.

You will also need to restart any always-on tasks that use them -- just disable them, then enable them again. Scheduled tasks that use virtualenvs will pick them up the next time they run.

6) All done!

We're here to help! If you get stuck or confused, just drop us a note at, and we'll be happy to help.