[Fab-user] Virtualenv Use Case

[s s]

Here's one of my use cases that I'd like to get up on the Wiki at some  
point for discussion.

We are deploying a django app to cloud servers.

The servers come up pretty vanilla on one particular provider; we  
can't set up boot images.

We need to put up a Python virtual environment, activate it, then  
install a bunch of Python stuff into it.

Since "run()" gets a whole new shell each time, you can't carry-over  
the environment and end up having to re-establishing the virtual  
environment each time.  I'm not a Capistrano user, only having played  
with it for a little while a few months ago, but it appears that  
Capistrano partially handles this with "cap shell."
        
        What I want is something like:
                runner=BatchRunner()
                runner.addCommand("cd my-new-virtualenv")
                runner.addCommand("bin/activate")
                runner.addCommand("easy_install 
some_project_into_my_virtual_env")
		runner.addCommand("easy_install  
some_other_project_into_my_virtual_env")
                runner.run()

        Or, even better:
                shell_commands = """
cd my-new-virtualenv
bin/activate
easy_install some_project_into_my_virtual_env
easy_install some_other_project_into_my_virtual_env
"""
                runner=BatchRunner()
                runner.addCommand("some_pre_command") # I can add one to the 
beginning
                runner.addCommands(shell_commands)              # then add my 
batch commands
		runner.addCommand("some_post_command")	# I can add one to the end if  
I want
                runner.run()

        Or, even:
                batchCommandsRunner=BatchRunner(shell_commands)
                runner=BatchRunner()
                runner.addCommand("some_pre_command") # I can add one to the 
beginning
                runner.addCommands(batchCommandsRunner) # then add my batch 
commands
		runner.addCommand("some_post_command")	# I can add one to the end if  
I want
                runner.run()
                
That way all the commands can be run, in sequence, but without causing  
multiple connections or having to re-establish the environment.  The  
third syntax allows easy combinations of pre-configured BatchRunners,  
even add-on module type ones.

I'm excited to see this moving forward right at the time.   I've got  
this and some other really strong use-cases and some time to put in to  
help make it work.

S