Custom status codes in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom status code in Flask?

A custom status code is a user-defined HTTP response code sent from a Flask route to indicate a specific result or error beyond standard codes.

beginner

How do you return a custom status code from a Flask route?

Return a tuple from the route with the response body and the custom status code number, e.g., return 'Error', 499.

intermediate

Why might you use a custom status code in a Flask app?

To communicate specific application states or errors not covered by standard HTTP codes, helping clients handle responses better.

intermediate

Can Flask recognize custom status codes automatically?

Flask allows any integer as a status code, but custom codes are not standard and may not be recognized by browsers or tools.

beginner

Show a simple Flask route example returning a custom status code 450.

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return 'Custom status', 450

How do you specify a custom status code in a Flask route return?

A Set a global variable with the status code

B Return a tuple with response and status code, e.g., return 'OK', 299

C Use a decorator to define the status code

D Flask does not support custom status codes

In Flask, returning a tuple with the response and status code sets the HTTP status code.

What happens if you use a non-standard status code in Flask?

A Flask converts it to 200 OK

B Flask will reject the response

C The code is sent but may not be understood by browsers

D The server crashes

Flask sends the code, but browsers or clients may not recognize it.

Which of these is a valid way to return a custom status code 499 in Flask?

A return 'Error', 499

B return 'Error', status=499

C return Response('Error', status_code=499)

D return 'Error'.status(499)

Returning a tuple with the response and status code is the correct Flask pattern.

Why should you be careful using custom status codes?

A They might confuse clients or tools expecting standard codes

B They always cause server errors

C They are slower to send

D They require special Flask plugins

Custom codes may not be recognized by clients, causing confusion.

Which HTTP status code range is typically used for custom codes?

A 100-199

B 200-299

C 400-499

D There is no official range for custom codes

Custom codes have no official range but often use unused numbers in 4xx or 5xx.

Explain how to return a custom status code in a Flask route and why you might do it.

Think about how Flask returns responses and why custom codes help.

Describe potential issues when using custom status codes in Flask applications.

Consider how browsers and APIs handle unknown codes.