Query parameter versioning in Rest API - Mini Project: Build & Apply

Query Parameter Versioning in a REST API

📖 Scenario: You are building a simple REST API that returns a greeting message. You want to support different versions of the API using query parameters.For example, /greet?version=1 returns a basic greeting, and /greet?version=2 returns a more detailed greeting.

🎯 Goal: Create a REST API endpoint /greet that reads the version query parameter and returns the correct greeting message based on the version number.

📋 What You'll Learn

Create a dictionary called greetings with keys as version numbers (integers) and values as greeting messages (strings).

Create a variable called default_version set to 1.

Write a function called get_greeting that takes a version parameter and returns the greeting message from the greetings dictionary or a default message if the version is not found.

Print the greeting message for the version passed as a query parameter.

💡 Why This Matters

🌍 Real World

APIs often need to support multiple versions so that older clients can still work while new features are added. Using query parameters for versioning is one simple way to do this.

💼 Career

Understanding how to handle API versioning is important for backend developers and anyone working with web services to ensure smooth upgrades and backward compatibility.

1

Create the greetings dictionary

Create a dictionary called greetings with these exact entries: 1: 'Hello!', 2: 'Hello, welcome to version 2 of our API!'

Rest API

# Create the greetings dictionary
# Your code here

Hint

Use curly braces {} to create a dictionary with keys 1 and 2 and their greeting messages.

2

Set the default version

Create a variable called default_version and set it to 1.

Rest API

greetings = {1: 'Hello!', 2: 'Hello, welcome to version 2 of our API!'}
# Set the default_version variable
# Your code here

Hint

Just assign the number 1 to the variable default_version.

3

Write the get_greeting function

Write a function called get_greeting that takes a parameter version and returns the greeting message from the greetings dictionary if the version exists, or returns 'Hello!' if the version is not found.

Rest API

greetings = {1: 'Hello!', 2: 'Hello, welcome to version 2 of our API!'}
default_version = 1

def get_greeting(version):
    # Your code here

Hint

Use the dictionary get method to return the greeting or a default message.

4

Print the greeting for a query parameter version

Assume a variable query_version holds the version number from the query parameter. Set query_version to 2. Then print the greeting message by calling get_greeting(query_version).

Rest API

greetings = {1: 'Hello!', 2: 'Hello, welcome to version 2 of our API!'}
default_version = 1

def get_greeting(version):
    return greetings.get(version, 'Hello!')

query_version = 2
# Your code here

Hint

Assign 2 to query_version and print the result of get_greeting(query_version).

Practice

1. What is the main purpose of using query parameter versioning in REST APIs?

easy

A. To change the main URL path for each API version

B. To allow clients to specify which API version they want using a query string

C. To hide the API version from clients

D. To force all clients to use the latest API version only

Solution

1. Step 1: Understand query parameter versioning concept

   Query parameter versioning lets clients add a version number in the URL query string, like ?version=1.

2. Step 2: Identify the purpose of this method

   This allows clients to choose which API version to use without changing the main URL path.

3. Final Answer:

   To allow clients to specify which API version they want using a query string -> Option B

4. Quick Check:

   Query parameter versioning = client selects version [OK]

Hint: Version in query string means client chooses API version [OK]

Common Mistakes:

• Thinking versioning changes the main URL path
• Assuming versioning hides API versions
• Believing all clients must use latest version only

2. Which of the following is the correct way to request version 2 of an API using query parameter versioning?

easy

A. GET /api/resource/version=2

B. GET /api/version/2/resource

C. GET /api/resource?version=2

D. GET /api/resource#version=2

Solution

1. Step 1: Recall query parameter syntax in URLs

   Query parameters come after a question mark ? and use key=value pairs, e.g., ?version=2.

2. Step 2: Match the correct syntax for versioning

   The correct way to specify version 2 is by adding ?version=2 after the resource path.

3. Final Answer:

   GET /api/resource?version=2 -> Option C

4. Quick Check:

   Query param syntax = ?key=value [OK]

Hint: Query parameters start with ? and use key=value [OK]

Common Mistakes:

• Using slashes instead of query parameters
• Using # instead of ? for query parameters
• Placing version inside the URL path incorrectly

3. Given this API endpoint code snippet handling versioning:

def get_data(request):
    version = request.GET.get('version', '1')
    if version == '1':
        return 'Data from v1'
    elif version == '2':
        return 'Data from v2'
    else:
        return 'Unknown version'

What will be the output if the client calls /api/data?version=2?

medium

A. "Data from v2"

B. "Unknown version"

C. "Data from v1"

D. Error: version parameter missing

Solution

1. Step 1: Extract version from query parameters

   The code gets the version from the query string. If missing, it defaults to '1'. Here, version='2'.

2. Step 2: Check version conditions

   Since version is '2', the code returns 'Data from v2'.

3. Final Answer:

   "Data from v2" -> Option A

4. Quick Check:

   version=2 returns v2 data [OK]

Hint: Check query param value matches version condition [OK]

Common Mistakes:

• Assuming default version is always used
• Confusing string and integer comparison
• Expecting error when version is provided

4. Consider this code snippet for versioning:

def api_handler(request):
    version = request.GET['version']
    if version == '1':
        return 'Version 1'
    else:
        return 'Other version'

What error will occur if the client calls /api/data without a version parameter?

medium

A. KeyError because 'version' key is missing

B. SyntaxError in code

C. Returns 'Version 1' by default

D. Returns 'Other version'

Solution

1. Step 1: Understand how version is accessed

   The code uses request.GET['version'] which raises KeyError if 'version' is missing.

2. Step 2: Analyze call without version parameter

   Calling without ?version=... means 'version' key is missing, causing KeyError.

3. Final Answer:

   KeyError because 'version' key is missing -> Option A

4. Quick Check:

   Missing key access causes KeyError [OK]

Hint: Access query keys safely to avoid KeyError [OK]

Common Mistakes:

• Assuming default version is used automatically
• Expecting no error when parameter is missing
• Confusing KeyError with SyntaxError

5. You want to support versions 1 and 2 of your API using query parameter versioning. Version 1 returns a list of users as strings, and version 2 returns a list of user objects with 'name' and 'id'. Which approach correctly handles this in a single endpoint?

hard

A. Return an error if version parameter is missing or unknown

B. Change the URL path to /v1/users and /v2/users instead of query parameters

C. Ignore the version parameter and always return the latest format

D. Use ?version=1 to return ['Alice', 'Bob'], and ?version=2 to return [{'name':'Alice','id':1},{'name':'Bob','id':2}]

Solution

1. Step 1: Understand query parameter versioning usage

   Clients specify version using ?version=1 or ?version=2 in the same URL.

2. Step 2: Return different data formats based on version

   Return simple list of strings for version 1, and detailed objects for version 2, matching client request.

3. Final Answer:

   Use ?version=1 to return ['Alice', 'Bob'], and ?version=2 to return [{'name':'Alice','id':1},{'name':'Bob','id':2}] -> Option D

4. Quick Check:

   Query param version controls response format [OK]

Hint: Return data format based on version query param [OK]

Common Mistakes:

• Changing URL path instead of using query parameters
• Ignoring version parameter and mixing formats
• Returning errors unnecessarily for missing versions