You don't need a shell script to initialise an application with specific environmental variables. systemd and docker will both do this (and both supports the same env file too). AWS lambda supports environmental variables, so does most CI/CD solutions. It's a pretty standard way to do things in UNIX/Linux. In fact if you're having to resort to "hacks" to get environmental variables loaded then that might be a symptom of a bigger problem with your orchestration rather than an issue with Bash / Python.

Also that was just one of three options I listed; and there will be a plethora of other alternatives I've not mentioned too.