Handling errors
Introduction to FastAPI
Matt Eckerle
Software and Data Leader
Two Main Reasons To Handle Errors
User error
- Invalid or outdated URI
- Missing or incorrect input
@app.delete("/items")
def delete_item(item: Item):
if item.id not in item_ids:
# Return an error
else:
crud.delete_item(item)
return {}
Server error
- Something else happened
@app.delete("/items")
def delete_item(item: Item):
try:
crud.delete_item(item)
except Exception:
# Return an error
return {}
HTTP Status Codes: "Levels of Yelling"
- Enables API to provide status in response
- Success, failure, error, etc.
- Specific codes defined in HTTP protocol
- Range:
100-599 - Categorize by first number (
1-5)
- Informational responses (
100-199) - Successful responses (
200-299) - Redirection messages (
300-399) - Client error responses (
400-499) - Server error responses (
500-599)
1 https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
Common HTTP Status Codes
Success (200 - 299)
200 OK- Default success response
201 Created- Specific to POST operation
202 Accepted- Noncommittal. "Working on it"
204 No Content- Success! Nothing more to say
Other responses
301 Moved Permantently- URI changed permanently
400 Bad Request- Client error
404 Not Found- Server cannot find the requested resource
500 Internal Server Error- Server has encountered a situation it does not know how to handle
Handling Errors With Status Codes
from fastapi import FastAPI, HTTPException
app = FastAPI()
@app.delete("/items")
def delete_item(item: Item):
if item.id not in item_ids:
# Send response with status 404 and specific error message
raise HTTPException(status_code=404, detail="Item not found.")
else:
delete_item_in_database(item)
return {}
Let's practice!
Introduction to FastAPI
