HTTPException & Custom Handlers in Python

From the FastAPI cheat sheet · Error Handling · verified Jul 2026

HTTPException & Custom Handlers

Return proper error responses and handle exceptions globally.

python

from fastapi import HTTPException

@app.get("/items/{item_id}")
async def read_item(item_id: int):
    if item_id not in items:
        raise HTTPException(status_code=404, detail="Item not found")
    return items[item_id]

💡 HTTPException is the standard way to return error responses in FastAPI

⚡ Use @app.exception_handler() to catch custom exceptions globally

📌 Override RequestValidationError handler to customize 422 validation responses

🟢 You can add custom headers to HTTPException for debugging or auth flows

errorsexceptionshttp

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