Set environment variables in a python script and use them in a chained call

I would like to set a couple of environment variables in a Python script, then use said environment variables in a chained call.

For example, a python script called set_env.py:

os.environ["MY_VAR"] = "cool value"

And then in bash

python ./set_env.py && echo "$MY_VAR"

Is such a thing possible?

I’ve tried to use the os.environ, os.system using export MY_VAR=..., but none of them seem to work.