With bash, you can create a generic virtual env wrapper that you can use to invoke any command, much like how time can wrapper any command.

virt_env_wrapper.bash:

#!/bin/bash    source path/to/virtual/env/bin/activate"$@"

Bash's magical incantation "$@" re-escapes all tokens on the original command line so that if you were to invoke:

virt_env_wrapper.bash python foo.py bar 'baz blap'

foo.py would see a sys.argv of ['bar', 'baz blap']