Query parameter versioning in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this API version check?

Given this Python Flask snippet that checks API version from query parameters, what will be the response if the request URL is /api/resource?version=2?

Rest API

from flask import Flask, request, jsonify
app = Flask(__name__)

@app.route('/api/resource')
def resource():
    version = request.args.get('version', '1')
    if version == '1':
        return jsonify({'message': 'Version 1 response'})
    elif version == '2':
        return jsonify({'message': 'Version 2 response'})
    else:
        return jsonify({'error': 'Unsupported version'}), 400

A 500 Internal Server Error

B {"message": "Version 2 response"}

C {"error": "Unsupported version"}

D {"message": "Version 1 response"}

💡 Hint

Check how the version parameter is read and matched in the code.

The code reads the 'version' query parameter. If it is '2', it returns the message for version 2. Since the URL has version=2, option B is correct.

🧠 Conceptual

intermediate

Which HTTP status code is best for unsupported API version?

When a client requests an API version that the server does not support using query parameter versioning, which HTTP status code should the server return?

A 400 Bad Request

B 404 Not Found

C 200 OK

D 500 Internal Server Error

💡 Hint

Think about client errors vs server errors.

A 400 Bad Request indicates the client sent a request with invalid parameters, such as an unsupported version. This is more appropriate than 404 or 500.

🔧 Debug

advanced

Why does this version check always return unsupported version response?

This Flask code is intended to return different responses based on the 'version' query parameter. But it always returns the unsupported version response, even when version=2 is requested. What is the bug?

Rest API

from flask import Flask, request, jsonify
app = Flask(__name__)

@app.route('/api/data')
def data():
    version = request.args.get('version')
    if version == 1:
        return jsonify({'message': 'Version 1 data'})
    elif version == 2:
        return jsonify({'message': 'Version 2 data'})
    else:
        return jsonify({'error': 'Unsupported version'}), 400

A The version variable is a string, but compared to integers 1 and 2, so conditions never match.

B The else block is missing a return statement.

C The jsonify function is used incorrectly without parentheses.

D The route decorator is missing a trailing slash causing routing issues.

💡 Hint

Check the data type of the version variable and the comparisons.

request.args.get returns a string. Comparing string '2' to integer 2 is false, so the code always falls to else.

📝 Syntax

advanced

Which option causes a syntax error in this version check?

Identify which code snippet will cause a syntax error when checking the API version from query parameters.

Rest API

version = request.args.get('version', '1')
if version == '1':
    return 'v1'
elif version == '2':
    return 'v2'
else:
    return 'unsupported'

A

if version == '1':
    return 'v1'

B if version == '1': return 'v1'

C if version = '1': return 'v1'

D

if version == '1'
    return 'v1'

💡 Hint

Remember the difference between assignment and comparison operators.

Option C uses a single equals sign (=) in the if condition, which is assignment and causes a syntax error. Conditions require == for comparison.

🚀 Application

expert

How many distinct responses does this API produce for versions 1 to 3?

Consider this Flask API code snippet that uses query parameter versioning. How many distinct JSON responses can this API produce when the version parameter is 1, 2, or 3?

Rest API

from flask import Flask, request, jsonify
app = Flask(__name__)

@app.route('/api/item')
def item():
    version = request.args.get('version', '1')
    match version:
        case '1':
            return jsonify({'data': 'Item v1'})
        case '2':
            return jsonify({'data': 'Item v2'})
        case '3':
            return jsonify({'data': 'Item v3'})
        case _:
            return jsonify({'error': 'Unsupported version'}), 400

A 4

B 0

C 1

D 3

💡 Hint

Count the distinct JSON responses for versions 1, 2, and 3 only.

For versions 1, 2, and 3, the API returns three distinct JSON objects with 'data' keys. The error response is for other versions, not counted here.