Implementing API Versioning in Python with Flask

In the lifecycle of any web API, changes are inevitable. To manage these changes gracefully and avoid breaking existing clients, implementing API versioning is crucial. This challenge will guide you through building a basic API with versioning using the Flask framework in Python.

Problem Description

Your task is to create a simple RESTful API using Flask that supports versioning. This means clients should be able to specify which version of the API they want to interact with. We will focus on URL-based versioning, where the version number is part of the URL path (e.g., /v1/items, /v2/items).

Key Requirements:

• Create a Flask application.
• Implement at least two versions of an API endpoint (e.g., /items).
• Each version should have distinct logic or data structure if necessary, though for this challenge, you can simulate this.
• The API should respond with appropriate data and HTTP status codes.
• Handle requests for non-existent versions gracefully.

Expected Behavior:

• Requests to /v1/items should be handled by the logic for API version 1.
• Requests to /v2/items should be handled by the logic for API version 2.
• Requests to a non-existent version (e.g., /v3/items) should result in a 404 Not Found error.
• Requests to the base path (e.g., /items) should ideally redirect to the latest version or return a 404, depending on your design choice (for this challenge, a 404 is acceptable if a specific version is not provided).

Edge Cases to Consider:

• What happens if a client requests a version that hasn't been implemented yet?
• How will you ensure consistency in error handling across different versions?

Examples

Example 1: Accessing API Version 1

Input: GET /v1/items
Output:
{
  "version": "1.0",
  "message": "Welcome to API v1!",
  "data": ["item1_v1", "item2_v1"]
}
Status Code: 200 OK

Explanation: The client requests the /items endpoint for version 1. The server successfully routes the request to the v1 handler, returning a JSON response indicating the version and sample data.

Example 2: Accessing API Version 2

Input: GET /v2/items
Output:
{
  "version": "2.0",
  "message": "Welcome to API v2! Enhanced features available.",
  "data": ["itemA_v2", "itemB_v2", "itemC_v2"]
}
Status Code: 200 OK

Explanation: The client requests the /items endpoint for version 2. The server routes the request to the v2 handler, returning a different JSON response reflecting the changes in v2.

Example 3: Requesting a Non-Existent Version

Input: GET /v3/items
Output:
{
  "error": "API version not found"
}
Status Code: 404 Not Found

Explanation: The client requests /items for version 3, which is not implemented. The server returns a 404 Not Found error with a descriptive JSON message.

Constraints

• The Flask application must be runnable.
• You should use standard Python libraries and Flask. No external libraries specifically for API versioning are required for this basic implementation.
• Responses should be in JSON format.
• HTTP status codes must be used correctly.

Notes

• Consider how you will organize your routes to handle different versions. You might use blueprints or simply define separate routes for each version.
• Think about how to make your code maintainable as you add more versions.
• For this challenge, you don't need to implement full CRUD operations. Simply returning different JSON responses for each version is sufficient to demonstrate the concept.