Revisiting Flask

• Following
  • PART 1
  • PART 2

Connexion module

• allows a python program to use the OpenAPI specification with Swagger.
• The OpenAPI specification is an API description format for REST APIs and provides a lot of functionality including:
  • Validation of i/p and o/p data to and from our API
  • Configuration of the API URL endpoints and the expected parameters
• When we use OpenAPI with Swagger, we can create a user interface to explore the API.
• All of this can happen when we create a configuration file that our flask application can access swagger.yaml

Add connexion to the App

• There are 2 steps to adding a REST API URL endpoint to our Flask application with Connexion:

  • Add an API configuration file to our project (swagger.yaml)

  • Connect our Flask app with the configuration file

    • we'll use connexion to create the application instance rather than Flask

    import connexion
    app = connexion.App(__name__, specification_dir="./")
    app.add_api("swagger.yaml")

Flask-Marshmallow

• This extends the Marshmallow library and provides additional features when we work with Flask
• Marshmallow is a serializer that converts complex data types to and from python data types
  • we can then use this functionality to serialize and deserialize Python objects as they flow in and out of our REST API, which is based on JSON
  • Marshmallow converts Python class instances to objects that can be converted to JSON
• flask-marshmallow[sqlalchemy] using the sqlalchemy option we can aslo install packages that helps our flask app leverage the powers of SQLAlchemy
  • Because SQLAlchemy returns data as Python class instances, Connexion can't serialize these class instances to JSON-formatted data
    • Here, serializing means converting python objects, which can contain other Python objects and complex data types, into simpler data structures that can be parsed into JSON data types
    • our Person class contains a timestamp, which is a Python DateTime Class. There's no DateTime definition in JSON, so the timestamp has to be converted to a string in order to exist in JSON structure
• Marshmallow helps us to create a PersonSchema class, which is like the SQLAlchemy Person class that we created.
  • The PersonSchema class defines how the attributes of a class will be converted into JSON-friendly format
  • Marshmallow also makes sure that all attributes are present and contain the expected data type

Useful things

• localhost:8000/api/ui to see our API documentation in action

SQLite database

• run the sqlite_setup.py script

• check if the table is setup properly run sqlite_check.py script

• to view the data: