No response returned FastAPI

Why This Happens

In FastAPI, the endpoint function didn't return anything. This is one of the most common FastAPI errors developers encounter. Understanding the root cause helps you fix it quickly and prevent it from recurring.

The Problem

@app.get('/items')
async def list_items():
    items = get_items()
    # Forgot return!

The Fix

@app.get('/items')
async def list_items():
    items = get_items()
    return items

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: No response returned. This tells you exactly what went wrong.

2. 2

   Find the cause

   Check the stack trace to find which line of your FastAPI code triggered this error.

3. 3

   Apply the fix

   Use the corrected code pattern shown above. Test to confirm the error is resolved.