Get root path of Flask application

app.root_path contains the root path for the application. This is determined based on the name passed to Flask. Typically, you should use the instance path (app.instance_path) not the root path, as the instance path will not be within the package code.

filename = os.path.join(app.instance_path, 'my_folder', 'my_file.txt')

app.root_path is the absolute path to the root directory containing your app code.

app.instance_path is the absolute path to the instance folder. os.path.dirname(app.instance_path) is the directory above the instance folder. During development, this is next to or the same as the root path, depending on your project layout.