Neither Flask nor Flask-RESTful includes the declaration of variables for the different HTTP status codes. We don't want to return numbers as status codes. We want our code to be easy to read and understand, and therefore, we will use descriptive HTTP status codes. We will borrow the code that declares useful functions and variables related to HTTP status codes from the status.py file included in Django REST Framework, that is, the framework we have been using in the preceding chapters.

First, create a folder named api within the root folder for the recently created virtual environment, and then create a new status.py file within the api folder. The following lines show the code that declares functions and variables with descriptive HTTP status codes in the api/models.py file borrowed from the rest_framework.status module. We don't want to reinvent the wheel, and the module provides everything we need to work with HTTP status codes in our Flask-based API. The code file for the sample is included in the restful_python_chapter_05_01 folder:

def is_informational(code): 
    return code >= 100 and code <= 199 
 
 
def is_success(code): 
    return code >= 200 and code <= 299 
 
 
def is_redirect(code): 
    return code >= 300 and code <= 399 
 
 
def is_client_error(code): 
    return code >= 400 and code <= 499 
 
 
def is_server_error(code): 
    return code >= 500 and code <= 599 
 
 
HTTP_100_CONTINUE = 100 
HTTP_101_SWITCHING_PROTOCOLS = 101 
HTTP_200_OK = 200 
HTTP_201_CREATED = 201 
HTTP_202_ACCEPTED = 202 
HTTP_203_NON_AUTHORITATIVE_INFORMATION = 203 
HTTP_204_NO_CONTENT = 204 
HTTP_205_RESET_CONTENT = 205 
HTTP_206_PARTIAL_CONTENT = 206 
HTTP_300_MULTIPLE_CHOICES = 300 
HTTP_301_MOVED_PERMANENTLY = 301 
HTTP_302_FOUND = 302 
HTTP_303_SEE_OTHER = 303 
HTTP_304_NOT_MODIFIED = 304 
HTTP_305_USE_PROXY = 305 
HTTP_306_RESERVED = 306 
HTTP_307_TEMPORARY_REDIRECT = 307 
HTTP_400_BAD_REQUEST = 400 
HTTP_401_UNAUTHORIZED = 401 
HTTP_402_PAYMENT_REQUIRED = 402 
HTTP_403_FORBIDDEN = 403 
HTTP_404_NOT_FOUND = 404 
HTTP_405_METHOD_NOT_ALLOWED = 405 
HTTP_406_NOT_ACCEPTABLE = 406 
HTTP_407_PROXY_AUTHENTICATION_REQUIRED = 407 
HTTP_408_REQUEST_TIMEOUT = 408 
HTTP_409_CONFLICT = 409 
HTTP_410_GONE = 410 
HTTP_411_LENGTH_REQUIRED = 411 
HTTP_412_PRECONDITION_FAILED = 412 
HTTP_413_REQUEST_ENTITY_TOO_LARGE = 413 
HTTP_414_REQUEST_URI_TOO_LONG = 414 
HTTP_415_UNSUPPORTED_MEDIA_TYPE = 415 
HTTP_416_REQUESTED_RANGE_NOT_SATISFIABLE = 416 
HTTP_417_EXPECTATION_FAILED = 417 
HTTP_428_PRECONDITION_REQUIRED = 428 
HTTP_429_TOO_MANY_REQUESTS = 429 
HTTP_431_REQUEST_HEADER_FIELDS_TOO_LARGE = 431 
HTTP_451_UNAVAILABLE_FOR_LEGAL_REASONS = 451 
HTTP_500_INTERNAL_SERVER_ERROR = 500 
HTTP_501_NOT_IMPLEMENTED = 501 
HTTP_502_BAD_GATEWAY = 502 
HTTP_503_SERVICE_UNAVAILABLE = 503 
HTTP_504_GATEWAY_TIMEOUT = 504 
HTTP_505_HTTP_VERSION_NOT_SUPPORTED = 505 
HTTP_511_NETWORK_AUTHENTICATION_REQUIRED = 511 

The code declares five functions that receive the HTTP status code in the code argument and determine which of the following categories the status code belongs to: informational, success, redirect, client error, or server error categories. We will use the previous variables when we have to return a specific status code. For example, in case we have to return a 404 Not Found status code, we will return status.HTTP_404_NOT_FOUND, instead of just 404.