It's not a strictly Python problem. He's deploying new code with updated dependencies in a separate directory, while the original site is running. If you manag

It's not a strictly Python problem. He's deploying new code with updated dependencies in a separate directory, while the original site is running. If you manage globally the dependencies you would probably brake the running version of the site during deploy, because it may expects different (old) API from his dependencies. For example the new code may NOT require a previously used dependency, and thus the deploy would remove it and the running code would collapse. Also, if the deploy fail midway you'd like the global environment to be unaffected.