Header-based versioning in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Flask API versioning code?

Consider this Flask API snippet using header-based versioning. What JSON response will the client receive when sending a request with header 'Accept-Version: v2'?

Rest API

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

@app.route('/data')
def data():
    version = request.headers.get('Accept-Version', 'v1')
    if version == 'v1':
        return jsonify({'message': 'Data from version 1'})
    elif version == 'v2':
        return jsonify({'message': 'Data from version 2', 'extra': 'Additional info'})
    else:
        return jsonify({'error': 'Unsupported version'}), 400

# Assume client sends header: Accept-Version: v2

A {"message": "Data from version 2", "extra": "Additional info"}

B HTTP 404 Not Found

C {"error": "Unsupported version"}

D {"message": "Data from version 1"}

💡 Hint

Check the header value and which branch the code executes.

The code checks the 'Accept-Version' header. If it is 'v2', it returns the JSON with message 'Data from version 2' and extra info. Other versions return different responses.

🧠 Conceptual

intermediate

Which header is commonly used for header-based API versioning?

In header-based versioning for REST APIs, which HTTP header is typically used to specify the API version?

A Authorization

B Content-Type

C Accept-Version

D User-Agent

💡 Hint

It is a custom header indicating the version the client wants.

The 'Accept-Version' header is commonly used to specify the API version in header-based versioning.

🔧 Debug

advanced

What error does this header-based versioning code raise?

This code snippet tries to read the API version from headers but has a bug. What error occurs when a request without the 'Accept-Version' header is sent?

Rest API

def get_version(request):
    version = request.headers['Accept-Version']
    if version == 'v1':
        return 'Version 1'
    else:
        return 'Other version'

# Request without 'Accept-Version' header

A KeyError

B TypeError

C ValueError

D No error, returns 'Other version'

💡 Hint

Accessing a missing dictionary key without a default causes an error.

Accessing request.headers['Accept-Version'] when the header is missing raises a KeyError.

📝 Syntax

advanced

Which option correctly extracts the API version from headers with a default fallback?

Choose the code snippet that safely gets the 'Accept-Version' header from a request, defaulting to 'v1' if missing.

A version = request.headers['Accept-Version'] or 'v1'

B version = request.headers.get('Accept-Version', 'v1')

C version = request.headers.get('Accept-Version') if 'Accept-Version' in request.headers else 'v1'

D version = request.headers['Accept-Version'] if request.headers['Accept-Version'] else 'v1'

💡 Hint

Use the dictionary get method with a default value.

Option B uses the .get() method with a default, which safely returns 'v1' if the header is missing.

🚀 Application

expert

How many different JSON keys are in the combined responses of this header-based versioning API?

Given this API code, how many unique JSON keys appear in all possible successful responses combined?

Rest API

def api_response(version):
    if version == 'v1':
        return {'status': 'ok', 'data': [1, 2, 3]}
    elif version == 'v2':
        return {'status': 'ok', 'data': [1, 2, 3], 'meta': {'count': 3}}
    elif version == 'v3':
        return {'status': 'ok', 'items': [1, 2, 3], 'meta': {'count': 3}}
    else:
        return {'error': 'Invalid version'}

# Consider only successful responses (no 'error' key)

A 6

B 5

C 3

D 4

💡 Hint

List all keys from each successful response and count unique ones.

Successful responses have keys: v1: status, data; v2: status, data, meta; v3: status, items, meta. Unique keys are status, data, meta, items → 4 keys total. But careful: v1 has 2 keys, v2 adds meta (3 keys), v3 replaces data with items (still unique), so total unique keys are status, data, meta, items → 4 keys. The question asks for combined unique keys, so answer is 4.