Fast API Training

A repo dedicated to training the team the concepts around Fast API development.

Slide deck

A slide deck accompanies the code. The pdf export is contained in the root directory.

The Google Slides are available to those in the company.

Prerequisites

• Python 3.8: See Install Instructions
• Docker: See Install Instructions
• Pipenv: See Install Instructions

1 - Hello World Fast API

In this lesson we will learn about the basics of creating a RESTful API with the FastAPI micro-web framework.

$ cd src/1-hello-world-api

Setup Virtual Environment

$ python3 -m venv .venv
$ source .venv/bin/activate

Install Requirements

$ pip install -r requirements.txt

Run the API

$ uvicorn app.main:app --reload

Navigate to http://127.0.0.1:8000/items/1

Documentation

Redoc documentation using OpenAPI can be found at http://127.0.0.1:8000/redoc

Run the Tests

$ pytest tests

Run Tests with Coverage Report

$ pytest --cov app

Exercises

Below are coding exercises to be completed with your group. See the FastAPI documentation for reference.

Exercise 1

Write a test for get_item function.

Exercise 2

Create a new endpoint which returns all items.

Write a test to check the response.

Exercise 3

Create a new endpoint which adds a new item to the list. Use the Fast API field validation to validate inputs.

• The name value should be a valid string.
• The age value should be a valid int.

Return the added item in the response.

Write a test to check your inputs.

Exercise 4

Create a new endpoint which allows the age value to be updated.

Return the updated item in the response.

Write a test to check that the value is updated.

Exercise 5

Create an endpoint which deletes an item by its index.

Write a test to check that the item is deleted.

2 - Pydantic Models

In this lesson we'll discuss creating Pydantic data models for data integrity and validation.

$ cd src/2-pydantic-models

Install Requirements with Pipenv

See Pipenv install instructions.

Run the command below to install the dependencies along with the development dependencies.

$ pipenv install --dev

Once the dependencies are installed, you will need to start the Pipenv shell.

$ pipenv shell

Run the App

Like in the previous example, start the app with:

$ uvicorn app.main:app --reload

Exercises

When you complete the exercises below, the tests should all pass

$ pytest tests

Exercise 1

Open the app/main.py file.

Look for the items variable, change the dict values into Pydantic models using the PersonModel

Hint: set one item to use a fixed uuid value of 5152cda2-db25-4338-8ffa-77923f2c885f.

uuid.UUID("5152cda2-db25-4338-8ffa-77923f2c885f")

Exercise 2

Open the app/main.py file.

Replace the generic dict type with the PersonModel to validate an object posted to the /items endpoint.

Exercise 3

Open the app/models.py file.

Update only the AddressModel used for updating a person's address while maintaining their original Uuid, name and age properties.

The new model should contain the following fields:

• street: string - default to empty string
• house_no: string - default to empty string
• postal_code: string - default to empty string
• city: string - default to empty string
• country: string - default to empty string

Fast API with Domain Driven Design (DDD)

$ cd src/3-ddd-api

The code in this example follows the Domain Driven Design pattern.

In short, Domain-driven design (DDD) is the concept that the structure and language of software code (class names, class methods, class variables) should match the business domain. For example, if a software processes loan applications, it might have classes such as LoanApplication and Customer, and methods such as AcceptOffer and Withdraw.

In this example the domain classes are stored in the apps/api/domain directory as pure classes. The persistence layer is handled via adapters which are abstracted into their own classes. These are located in the apps/api/adapters directory.

The Context class loads the correct adapters, commands, and messagebus

Install Dependencies

$ pipenv install --dev
$ pipenv shell

Run the Tests

$ pytest tests

Applications

To show how DDD can be used in multiple applications, there is a RESTful API using FastAPI, and a CLI using Click.

FastApi

In a separate shell you can run the following command to start the FastAPI implementation.

$ uvicorn apps.api.entrypoint:app --reload

Click

In another shell you can run the following command to get and add a person to the same person repository used in the FastAPI implementation.

Add Person

PYTHONPATH=. python apps/cli/people.py add Henry 45

Get Person

PYTHONPATH=. python apps/cli/people.py get 60c2866a704fb00b25276344