How to export and ensure availability of variables from .env file on server start/restart in Python, Flask?
I had to put content of the file into envvars into Apache2 server. 
After I did this, I get everything working. I thought there is a Python way to export environment variables in Flask application while running on Apache2 but nothing worked for me.
Another solution I see but has never tried myself to add into Apache2 config SetEnv VAR_KEY VAR_VALUE alike statements.
How to export and ensure availability of variables from .env file on server start/restart in Python?
I have file .env with secured variables, such as passwords, credentials and confidential information. I want to make this variables available on the server start/restart.

How to load variables from .env in Python?
How to load/reload variables from .env in Python, when server is restarted, reloaded?
How to ensure that variables is always in operational memory?
Is there any other better way to do solve the same technical issue?

I am using Flask and run app on Apache2 using WSGI.
My file looks the following:

ENVIRONMENT_VARIABLE_EXAMPLE=SECRET_KEY