How to set virtualenv for a crontab?

I want to set up a crontab to run a Python script.

Say the script is something like:

#!/usr/bin/python
print "hello world"

Is there a way I could specify a virtualenv for that Python script to run in? In shell I'd just do:

~$ workon myenv

Is there something equivalent I could do in crontab to activate a virtualenv?