Status Codes
You can import the status module from fastapi:
from fastapi import status
 
status is provided directly by Starlette.
It contains a group of named constants (variables) with integer status codes.
For example:
- 200: 
status.HTTP_200_OK 
- 403: 
status.HTTP_403_FORBIDDEN 
- etc.
 
It can be convenient to quickly access HTTP (and WebSocket) status codes in your app, using autocompletion for the name without having to remember the integer status codes by memory.
Read more about it in the FastAPI docs about Response Status Code.
Example
from fastapi import FastAPI, status
app = FastAPI()
@app.get("/items/", status_code=status.HTTP_418_IM_A_TEAPOT)
def read_items():
    return [{"name": "Plumbus"}, {"name": "Portal Gun"}]
 
          fastapi.status
  
  
      HTTP codes
See HTTP Status Code Registry:
https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
And RFC 2324 - https://tools.ietf.org/html/rfc2324
  
  
          HTTP_100_CONTINUE
  
  
      module-attribute
  
  
  
 
          HTTP_101_SWITCHING_PROTOCOLS
  
  
      module-attribute
  
HTTP_101_SWITCHING_PROTOCOLS = 101
 
  
  
 
          HTTP_102_PROCESSING
  
  
      module-attribute
  
HTTP_102_PROCESSING = 102
 
  
  
 
          HTTP_103_EARLY_HINTS
  
  
      module-attribute
  
HTTP_103_EARLY_HINTS = 103
 
  
  
 
          HTTP_200_OK
  
  
      module-attribute
  
  
  
 
          HTTP_201_CREATED
  
  
      module-attribute
  
  
  
 
          HTTP_202_ACCEPTED
  
  
      module-attribute
  
  
  
 
HTTP_203_NON_AUTHORITATIVE_INFORMATION = 203
 
  
  
 
          HTTP_204_NO_CONTENT
  
  
      module-attribute
  
HTTP_204_NO_CONTENT = 204
 
  
  
 
          HTTP_205_RESET_CONTENT
  
  
      module-attribute
  
HTTP_205_RESET_CONTENT = 205
 
  
  
 
          HTTP_206_PARTIAL_CONTENT
  
  
      module-attribute
  
HTTP_206_PARTIAL_CONTENT = 206
 
  
  
 
          HTTP_207_MULTI_STATUS
  
  
      module-attribute
  
HTTP_207_MULTI_STATUS = 207
 
  
  
 
          HTTP_208_ALREADY_REPORTED
  
  
      module-attribute
  
HTTP_208_ALREADY_REPORTED = 208
 
  
  
 
          HTTP_226_IM_USED
  
  
      module-attribute
  
  
  
 
          HTTP_300_MULTIPLE_CHOICES
  
  
      module-attribute
  
HTTP_300_MULTIPLE_CHOICES = 300
 
  
  
 
          HTTP_301_MOVED_PERMANENTLY
  
  
      module-attribute
  
HTTP_301_MOVED_PERMANENTLY = 301
 
  
  
 
          HTTP_302_FOUND
  
  
      module-attribute
  
  
  
 
          HTTP_303_SEE_OTHER
  
  
      module-attribute
  
  
  
 
          HTTP_304_NOT_MODIFIED
  
  
      module-attribute
  
HTTP_304_NOT_MODIFIED = 304
 
  
  
 
          HTTP_305_USE_PROXY
  
  
      module-attribute
  
  
  
 
          HTTP_306_RESERVED
  
  
      module-attribute
  
  
  
 
          HTTP_307_TEMPORARY_REDIRECT
  
  
      module-attribute
  
HTTP_307_TEMPORARY_REDIRECT = 307
 
  
  
 
          HTTP_308_PERMANENT_REDIRECT
  
  
      module-attribute
  
HTTP_308_PERMANENT_REDIRECT = 308
 
  
  
 
          HTTP_400_BAD_REQUEST
  
  
      module-attribute
  
HTTP_400_BAD_REQUEST = 400
 
  
  
 
          HTTP_401_UNAUTHORIZED
  
  
      module-attribute
  
HTTP_401_UNAUTHORIZED = 401
 
  
  
 
          HTTP_402_PAYMENT_REQUIRED
  
  
      module-attribute
  
HTTP_402_PAYMENT_REQUIRED = 402
 
  
  
 
          HTTP_403_FORBIDDEN
  
  
      module-attribute
  
  
  
 
          HTTP_404_NOT_FOUND
  
  
      module-attribute
  
  
  
 
          HTTP_405_METHOD_NOT_ALLOWED
  
  
      module-attribute
  
HTTP_405_METHOD_NOT_ALLOWED = 405
 
  
  
 
          HTTP_406_NOT_ACCEPTABLE
  
  
      module-attribute
  
HTTP_406_NOT_ACCEPTABLE = 406
 
  
  
 
          HTTP_407_PROXY_AUTHENTICATION_REQUIRED
  
  
      module-attribute
  
HTTP_407_PROXY_AUTHENTICATION_REQUIRED = 407
 
  
  
 
          HTTP_408_REQUEST_TIMEOUT
  
  
      module-attribute
  
HTTP_408_REQUEST_TIMEOUT = 408
 
  
  
 
          HTTP_409_CONFLICT
  
  
      module-attribute
  
  
  
 
          HTTP_410_GONE
  
  
      module-attribute
  
  
  
 
          HTTP_411_LENGTH_REQUIRED
  
  
      module-attribute
  
HTTP_411_LENGTH_REQUIRED = 411
 
  
  
 
          HTTP_412_PRECONDITION_FAILED
  
  
      module-attribute
  
HTTP_412_PRECONDITION_FAILED = 412
 
  
  
 
          HTTP_413_REQUEST_ENTITY_TOO_LARGE
  
  
      module-attribute
  
HTTP_413_REQUEST_ENTITY_TOO_LARGE = 413
 
  
  
 
          HTTP_414_REQUEST_URI_TOO_LONG
  
  
      module-attribute
  
HTTP_414_REQUEST_URI_TOO_LONG = 414
 
  
  
 
HTTP_415_UNSUPPORTED_MEDIA_TYPE = 415
 
  
  
 
          HTTP_416_REQUESTED_RANGE_NOT_SATISFIABLE
  
  
      module-attribute
  
HTTP_416_REQUESTED_RANGE_NOT_SATISFIABLE = 416
 
  
  
 
          HTTP_417_EXPECTATION_FAILED
  
  
      module-attribute
  
HTTP_417_EXPECTATION_FAILED = 417
 
  
  
 
          HTTP_418_IM_A_TEAPOT
  
  
      module-attribute
  
HTTP_418_IM_A_TEAPOT = 418
 
  
  
 
          HTTP_421_MISDIRECTED_REQUEST
  
  
      module-attribute
  
HTTP_421_MISDIRECTED_REQUEST = 421
 
  
  
 
          HTTP_422_UNPROCESSABLE_ENTITY
  
  
      module-attribute
  
HTTP_422_UNPROCESSABLE_ENTITY = 422
 
  
  
 
          HTTP_423_LOCKED
  
  
      module-attribute
  
  
  
 
          HTTP_424_FAILED_DEPENDENCY
  
  
      module-attribute
  
HTTP_424_FAILED_DEPENDENCY = 424
 
  
  
 
          HTTP_425_TOO_EARLY
  
  
      module-attribute
  
  
  
 
          HTTP_426_UPGRADE_REQUIRED
  
  
      module-attribute
  
HTTP_426_UPGRADE_REQUIRED = 426
 
  
  
 
          HTTP_428_PRECONDITION_REQUIRED
  
  
      module-attribute
  
HTTP_428_PRECONDITION_REQUIRED = 428
 
  
  
 
          HTTP_429_TOO_MANY_REQUESTS
  
  
      module-attribute
  
HTTP_429_TOO_MANY_REQUESTS = 429
 
  
  
 
HTTP_431_REQUEST_HEADER_FIELDS_TOO_LARGE = 431
 
  
  
 
          HTTP_451_UNAVAILABLE_FOR_LEGAL_REASONS
  
  
      module-attribute
  
HTTP_451_UNAVAILABLE_FOR_LEGAL_REASONS = 451
 
  
  
 
          HTTP_500_INTERNAL_SERVER_ERROR
  
  
      module-attribute
  
HTTP_500_INTERNAL_SERVER_ERROR = 500
 
  
  
 
          HTTP_501_NOT_IMPLEMENTED
  
  
      module-attribute
  
HTTP_501_NOT_IMPLEMENTED = 501
 
  
  
 
          HTTP_502_BAD_GATEWAY
  
  
      module-attribute
  
HTTP_502_BAD_GATEWAY = 502
 
  
  
 
          HTTP_503_SERVICE_UNAVAILABLE
  
  
      module-attribute
  
HTTP_503_SERVICE_UNAVAILABLE = 503
 
  
  
 
          HTTP_504_GATEWAY_TIMEOUT
  
  
      module-attribute
  
HTTP_504_GATEWAY_TIMEOUT = 504
 
  
  
 
          HTTP_505_HTTP_VERSION_NOT_SUPPORTED
  
  
      module-attribute
  
HTTP_505_HTTP_VERSION_NOT_SUPPORTED = 505
 
  
  
 
          HTTP_506_VARIANT_ALSO_NEGOTIATES
  
  
      module-attribute
  
HTTP_506_VARIANT_ALSO_NEGOTIATES = 506
 
  
  
 
          HTTP_507_INSUFFICIENT_STORAGE
  
  
      module-attribute
  
HTTP_507_INSUFFICIENT_STORAGE = 507
 
  
  
 
          HTTP_508_LOOP_DETECTED
  
  
      module-attribute
  
HTTP_508_LOOP_DETECTED = 508
 
  
  
 
          HTTP_510_NOT_EXTENDED
  
  
      module-attribute
  
HTTP_510_NOT_EXTENDED = 510
 
  
  
 
          HTTP_511_NETWORK_AUTHENTICATION_REQUIRED
  
  
      module-attribute
  
HTTP_511_NETWORK_AUTHENTICATION_REQUIRED = 511
 
  
  
      WebSocket codes
https://www.iana.org/assignments/websocket/websocket.xml#close-code-number
https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
   
 
          WS_1000_NORMAL_CLOSURE
  
  
      module-attribute
  
WS_1000_NORMAL_CLOSURE = 1000
 
  
  
 
          WS_1001_GOING_AWAY
  
  
      module-attribute
  
WS_1001_GOING_AWAY = 1001
 
  
  
 
          WS_1002_PROTOCOL_ERROR
  
  
      module-attribute
  
WS_1002_PROTOCOL_ERROR = 1002
 
  
  
 
          WS_1003_UNSUPPORTED_DATA
  
  
      module-attribute
  
WS_1003_UNSUPPORTED_DATA = 1003
 
  
  
 
          WS_1005_NO_STATUS_RCVD
  
  
      module-attribute
  
WS_1005_NO_STATUS_RCVD = 1005
 
  
  
 
          WS_1006_ABNORMAL_CLOSURE
  
  
      module-attribute
  
WS_1006_ABNORMAL_CLOSURE = 1006
 
  
  
 
          WS_1007_INVALID_FRAME_PAYLOAD_DATA
  
  
      module-attribute
  
WS_1007_INVALID_FRAME_PAYLOAD_DATA = 1007
 
  
  
 
          WS_1008_POLICY_VIOLATION
  
  
      module-attribute
  
WS_1008_POLICY_VIOLATION = 1008
 
  
  
 
          WS_1009_MESSAGE_TOO_BIG
  
  
      module-attribute
  
WS_1009_MESSAGE_TOO_BIG = 1009
 
  
  
 
          WS_1010_MANDATORY_EXT
  
  
      module-attribute
  
WS_1010_MANDATORY_EXT = 1010
 
  
  
 
          WS_1011_INTERNAL_ERROR
  
  
      module-attribute
  
WS_1011_INTERNAL_ERROR = 1011
 
  
  
 
          WS_1012_SERVICE_RESTART
  
  
      module-attribute
  
WS_1012_SERVICE_RESTART = 1012
 
  
  
 
          WS_1013_TRY_AGAIN_LATER
  
  
      module-attribute
  
WS_1013_TRY_AGAIN_LATER = 1013
 
  
  
 
          WS_1014_BAD_GATEWAY
  
  
      module-attribute
  
WS_1014_BAD_GATEWAY = 1014
 
  
  
 
          WS_1015_TLS_HANDSHAKE
  
  
      module-attribute
  
WS_1015_TLS_HANDSHAKE = 1015