The Importance of Order: Viewing in FastAPI #Python #SurenPyTips

In FastAPI, the order of the routes declared in your application is important. This is because FastAPI uses a "first match" algorithm to determine which route handler to invoke when a request is made. This means that the first route that matches the request will be the one that is executed.

To illustrate this concept, let’s consider the following example:

from fastapi import FastAPI

app = FastAPI()

# Route 1
@app.get("/items/")
async def get_items():
    return {"message": "Get all items"}

# Route 2
@app.get("/items/{item_id}")
async def get_item(item_id: int):
    return {"message": f"Get item with id {item_id}"}

In this example, we have two routes defined: /items/ and /items/{item_id}. If a request is made to /items/, FastAPI will match this route first and execute the get_items handler. However, if the request is made to /items/1, FastAPI will match the second route and execute the get_item handler instead.

If we were to swap the order of the routes, like so:

# Route 1
@app.get("/items/{item_id}")
async def get_item(item_id: int):
    return {"message": f"Get item with id {item_id}"}

# Route 2
@app.get("/items/")
async def get_items():
    return {"message": "Get all items"}

Now, if a request is made to /items/, FastAPI will still match the first route and execute the get_item handler because it was declared first. This is why it’s important to consider the order of your routes when defining them in FastAPI.

In general, it’s a good practice to organize your routes in a logical order that makes sense for your application. For example, you might want to group related routes together or put more specific routes before more general ones. This will help you avoid conflicts and make your code easier to read and maintain.

Overall, understanding the importance of the order of routes in FastAPI is crucial for building a reliable and efficient web application. By following best practices and being mindful of how routes are matched, you can ensure that your application behaves as expected and delivers a great user experience.