Activate a virtualenv via fabric as deploy user

Right now, you can do what I do, which is kludgy but works perfectly well* (this usage assumes you're using virtualenvwrapper -- which you should be -- but you can easily substitute in the rather longer 'source' call you mentioned, if not):

def task():
    workon = 'workon myvenv && '
    run(workon + 'git pull')
    run(workon + 'do other stuff, etc')

Since version 1.0, Fabric has a prefix context manager which uses this technique so you can for example:

def task():
    with prefix('workon myvenv'):
        run('git pull')
        run('do other stuff, etc')

---

* There are bound to be cases where using the command1 && command2 approach may blow up on you, such as when command1 fails (command2 will never run) or if command1 isn't properly escaped and contains special shell characters, and so forth.

As an update to bitprophet's forecast: With Fabric 1.0 you can make use of prefix() and your own context managers.

from __future__ import with_statement
from fabric.api import *
from contextlib import contextmanager as _contextmanager

env.hosts = ['servername']
env.user = 'deploy'
env.keyfile = ['$HOME/.ssh/deploy_rsa']
env.directory = '/path/to/virtualenvs/project'
env.activate = 'source /path/to/virtualenvs/project/bin/activate'

@_contextmanager
def virtualenv():
    with cd(env.directory):
        with prefix(env.activate):
            yield

def deploy():
    with virtualenv():
        run('pip freeze')