Each time you run something with a Process call, you are starting a Linux process, running it, and then terminating. The next Process invocation starts from scratch. There is no continuity from one Process invocation to the next. It's as if you logged in, ran the first command, then logged out; then logged back in, ran the second command, and logged out again. Setting the environment in the first Process will not affect the second Process.
If you need to run multiple commands in the same context, you need to do it in one Process invocation. I suggest that you write a shell script that does all of your steps: sets the environment variables, changes directories, runs your Python script, etc. Then run that shell script from your Process invocation.o