Flask supports multiple environments: development, testing and production. In this article you learn how to set the environment you want.

If you worked in software development jobs before, you may already be familiar with these.

Related course: Python Flask: Create Web Apps with Flask

Set environment

Types of environments

There is an important concept that needs our attention, which is that every configuration file is environment-related, that is, because there are multiple environments, multiple configurations are present.

If you don’t understand the meaning of this sentence, let’s look at the file names under the config directory, which can actually be divided into several categories:

  • development: a development environment that generally uses for local development environments

  • product: production environments for online deployment

  • testing: for test environments, general for various test uses

As we can see, we have a local environment in which we can develop debugging locally.

After you have tested it (in the testing environment) and completed of the tests, there will be an production environment.

Set environment

The mystery here is in the config/init.py file. Let’s take a look at this file:

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# coding: UTF-8
import os
def load_config(mode=os.environ.get('MODE')):
    """Load config."""
    try:
        if mode == 'PRODUCTION':
            from .production import ProductionConfig
            return ProductionConfig
        elif mode == 'TESTING':
            from .testing import TestingConfig
            return TestingConfig
        else:
            from .development import DevelopmentConfig
            return DevelopmentConfig
    except ImportError:
        from .default import Config
        return Config

In the config/init.py file, I define a load_config() function that accepts a mode parameter representing the configuration of what environment.

If this parameter is not passed, the MODE environment variable in the system environment variable is used by default, and then the specified configuration file is returned according to the specified environment.

If you do not have a specified configuration file, you can only return the default environment variable.

Similarly, if you need to add a custom environment configuration file, you need to simply modify the function, and specify that you can load the configuration files that you customize.

After you use the configuration load configuration to resolve this problem, next is using these configurations in our Flask application.

Because load_config() is all configured, the use is also not a big problem, here is an example:

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"""Create Flask app."""
config = load_config(mode)
app = Flask(__name__)
app.config.from_object(config)

The configuration is set using the config from_object() setting for the Flask object.It’s that simple.

Alternative

The above method works and is a good way to set an environment, but it’s not the only way.

By default if you start a Flask server, it is set to a certain environment mode.
This is displayed when you run the command flask example.py.

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* Serving Flask app "example" (lazy loading)
* Environment: production
  WARNING: This is a development server. Do not use it in a production deployment.
  Use a production WSGI server instead.
* Debug mode: off
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

In this case:

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* Environment: production

You can run the shell command

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export FLASK_ENV=development

This changes the environment to

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* Environment: production

You may want to set that in your .env file.

Related course: Python Flask: Create Web Apps with Flask