Handling basic configurations

The first thing that comes to mind is configuring a Flask application as per the need. In this recipe, we will try to understand the different ways in which Flask configurations can be done.

Getting ready

In Flask, a configuration is done on an attribute named config of the Flask object. The config attribute is a subclass of the dictionary data type, and we can modify it just like any dictionary.

How to do it…

For instance, to run our application in the debug mode, we can write the following:

app = Flask(__name__)
app.config['DEBUG'] = True

Tip

The debug Boolean can also be set at the Flask object level rather than at the config level:

app.debug = True

Alternatively, we can use this line of code:

app.run(debug=True)

Enabling the debug mode will make the server reload itself in the case of any code changes, and it also provides the very helpful Werkzeug debugger when something goes wrong.

There are a bunch of configuration values provided by Flask. We will come across them in the relevant recipes.

As the application grows larger, there originates a need to manage the application's configuration in a separate file as shown here. Being specific to machine-based setups in most cases will most probably not be a part of the version-control system. For this, Flask provides us with multiple ways to fetch configurations. The most frequently used ones are discussed here:

• From a Python configuration file (*.cfg), the configuration can be fetched using:

  app.config.from_pyfile('myconfig.cfg')

• From an object, the configuration can be fetched using:

  app.config.from_object('myapplication.default_settings')

  Alternatively, we can also use:

  app.config.from_object(__name__) #To load from same file

• From the environment variable, the configuration can be fetched using:

  app.config.from_envvar('PATH_TO_CONFIG_FILE')

How it works…

Flask is intelligent enough to pick up only those configuration variables that are written in uppercase. This allows us to define any local variables in our configuration files/objects and leave the rest to Flask.

Tip

The best practice to use configurations is to have a bunch of default settings in app.py or via any object in our application itself and then override the same by loading it from the configuration file. So, the code will look like this:

app = Flask(__name__)
DEBUG = True
TESTING = True
app.config.from_object(__name__)
app.config.from_pyfile('/path/to/config/file')