When you write Emacs plugin which uses Python script, you would want to setup Python modules for that script easily from Emacs. You can use python-environment.el to do that:

(require 'python-environment) (defun YOUR-PLUGIN-install-python-dependencies () (interactive) (python-environment-run "pip" "install" "epc")) 

In your plugin, if you want the path to command installed in the virtualenv, do something like this:

(start-process NAME BUFFER (python-environment-bin "COMMAND") ...) 

Path to access COMMAND may be different in *nix and in Windows, but python-environment.el finds the right path.