Exceptions -HTTPException andWebSocketException¶
These are the exceptions that you can raise to show errors to the client.
When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.
You can use:
HTTPExceptionWebSocketException
These exceptions can be imported directly fromfastapi:
fromfastapiimportHTTPException,WebSocketException
HTTPException(status_code,detail=None,headers=None) Bases:HTTPException
An HTTP exception you can raise in your own code to show errors to the client.
This is for client errors, invalid authentication, invalid data, etc. Not for servererrors in your code.
Read more about it in theFastAPI docs for Handling Errors.
Example¶
fromfastapiimportFastAPI,HTTPExceptionapp=FastAPI()items={"foo":"The Foo Wrestlers"}@app.get("/items/{item_id}")asyncdefread_item(item_id:str):ifitem_idnotinitems:raiseHTTPException(status_code=404,detail="Item not found")return{"item":items[item_id]}| PARAMETER | DESCRIPTION |
|---|---|
status_code | HTTP status code to send to the client. Read more about it in theFastAPI docs for Handling Errors TYPE: |
detail | Any data to be sent to the client in the Read more about it in theFastAPI docs for Handling Errors TYPE: |
headers | Any headers to send to the client in the response. Read more about it in theFastAPI docs for Handling Errors TYPE: |
Source code infastapi/exceptions.py
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WebSocketException(code,reason=None) Bases:WebSocketException
A WebSocket exception you can raise in your own code to show errors to the client.
This is for client errors, invalid authentication, invalid data, etc. Not for servererrors in your code.
Read more about it in theFastAPI docs for WebSockets.
Example¶
fromtypingimportAnnotatedfromfastapiimport(Cookie,FastAPI,WebSocket,WebSocketException,status,)app=FastAPI()@app.websocket("/items/{item_id}/ws")asyncdefwebsocket_endpoint(*,websocket:WebSocket,session:Annotated[str|None,Cookie()]=None,item_id:str,):ifsessionisNone:raiseWebSocketException(code=status.WS_1008_POLICY_VIOLATION)awaitwebsocket.accept()whileTrue:data=awaitwebsocket.receive_text()awaitwebsocket.send_text(f"Session cookie is:{session}")awaitwebsocket.send_text(f"Message text was:{data}, for item ID:{item_id}")| PARAMETER | DESCRIPTION |
|---|---|
code | A closing code from thevalid codes defined in the specification. TYPE: |
reason | The reason to close the WebSocket connection. It is UTF-8-encoded data. The interpretation of the reason is up to theapplication, it is not specified by the WebSocket specification. It could contain text that could be human-readable or interpretableby the client code, etc. TYPE: |
Source code infastapi/exceptions.py
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