Setting environment variables in virtualenv (Python, Windows)
Flask does not automatically take configuration variables from environment variables. You have to set them manually like so:
app.config.from_envvar('YOURAPPLICATION_SETTINGS')More info regarding configuration can be found here.
To set an environment variable in Windows, you should do as described here:
setx DATABASE_URL=sqlite://something.something
The problem was that PyCharm does not activate the virtualenvironment when pressing the run button. It only uses the virtualenv python.exe.