Is adding Flask env vars to the virtualenv's activate script OK?

Question

I\'m working on my Flask project in a virtualenv. Every time I start a new terminal, I have to reinitialize these Flask environment variables:

export FLASK         


        

Answer 1

Yes, setting environment variables in the virtualenv's activate script is fine for managing your development environment. It's described in Flask's docs. They're only active when the env is activated in the terminal, and you have to remember to add them if you create a new env, but there's nothing wrong with it.

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With Flask 1.0, you can use dotenv files instead. Install python-dotenv:

pip install python-dotenv

Add a .flaskenv file:

FLASK_APP=server

And the flask command will automatically set them when running a command:

flask run

The advantage of this over messing with the venv is that you can commit this file so it applies anywhere you work on the code.

Answer 2

Modifying venv/bin/activate file is working for you because the environment variable is getting defined inside the virtual environment. When you're using python3 -m venv venv the environment variables are not present in the new virtual environment. Instead of modifying the activate file, you can instead make a shell script which:

1. Runs venv/bin/activate
2. Defines the environment variables
3. Runs the server

First, I tried writing a Python script that set them, but after research, I realized it was not possible(?).

You could use os.environ to do the same from within, but a shell script is better.