No process can change its parent process (or any other existing process' environment).
You can, however, create a new environment by creating a new interactive shell with the modified environment.
You have to spawn a new copy of the shell that uses the upgraded environment and has access to the existing stdin, stdout and stderr, and does its reinitialization dance.
You need to do something like use subprocess.Popen to run /bin/bash -i
.
So the original shell runs Python, which runs a new shell. Yes, you have a lot of processes running. No it's not too bad because the original shell and Python aren't really doing anything except waiting for the subshell to finish so they can exit cleanly, also.
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