FastAPI MVC CRUD Build Update Route

Learning objective: By the end of this lesson, you will be able to implement the HTTP PUT method to update existing “tea” resources in a FastAPI project.

Introduction

The HTTP PUT method is commonly used to update existing resources on a server. In this lesson, you’ll use PUT to update the details of an existing tea in your mock database in the FastAPI app.

Implement the PUT method in FastAPI

Now, let’s implement the PUT method in our controllers/teas.py file to allow us to update existing tea resources.

1. Open the controllers/teas.py file.

2. Add the following code to implement the PUT method:

# teas.py

@router.put("/teas/{tea_id}")
def update_tea(tea_id: int, tea: dict):

    # Find the tea to update
    for existing_tea in teas_db['teas']:
        if existing_tea['id'] == tea_id:
            existing_tea.update(tea)  # Update the existing tea's data
            return existing_tea

    # If tea was not found, raise an error
    raise HTTPException(status_code=404, detail="Tea not found")

What is happening in this code?

• @router.put("/teas/{tea_id}"): This decorator creates a new PUT route at /teas/{tea_id}. The {tea_id} part is a URL parameter that identifies the specific tea to update.

• tea_id: int: This part indicates that the URL parameter tea_id should be an integer, representing the ID of the tea to update.

• tea: dict: This part indicates that the data sent in the PUT request must be a dictionary (in JSON format) with the updated values for the tea.

• existing_tea.update(tea): This updates the tea’s data with the new values passed in the request.

Testing the PUT method using FastAPI’s interactive documentation

FastAPI provides a built-in developer sandbox to test your API endpoints. You can use it to quickly try out your PUT method without writing any client-side code.

1. Start your FastAPI server if it’s not already running:

pipenv run uvicorn main:app --reload

1. Open your browser and navigate to http://127.0.0.1:8000/docs.

   This is FastAPI’s interactive API documentation. You’ll see a list of all available endpoints, including the PUT /api/teas/{tea_id} route.

2. Click on PUT /api/teas/{tea_id} to expand it.

3. Click the Try it out button. You’ll see fields where you can input the tea_id and the updated data for the tea.

4. In the tea_id field, enter the ID of the tea you want to update (ex: 1).

5. In the Request body field, paste the following JSON data to update the tea:

{
  "name": "chai latte",
  "in_stock": true,
  "rating": 4.8
}

1. Click the Execute button. This sends the PUT request to update the tea with the specified ID.

   • You should see a response with the 200 OK status, indicating the tea was successfully updated.

Verifying the updated tea

1. After executing the PUT request, navigate to http://127.0.0.1:8000/api/teas in your browser.

   • You should see the updated tea in the list, like this:

{
  "teas": [
    { "id": 1, "name": "chai latte", "in_stock": true, "rating": 4.8 },
    { "id": 2, "name": "lemongrass", "in_stock": true, "rating": 3.8 },
    { "id": 3, "name": "matcha", "in_stock": false, "rating": 4.4 }
  ]
}

You’ve successfully implemented the PUT method to update an existing tea. Now, let’s continue building the CRUD routes for a complete FastAPI app! In the upcoming lessons, we’ll focus on implementing the DELETE operation to remove teas from the database.