Why REST APIs exist - See It in Action

Understanding Why REST APIs Exist

📖 Scenario: Imagine you want to build a simple app that shows weather information from different cities. To get this data, your app needs to talk to a server that stores weather details. REST APIs help your app and the server communicate smoothly.

🎯 Goal: Learn why REST APIs exist by creating a simple example that shows how a client can request data from a server using REST principles.

📋 What You'll Learn

Create a simple data structure to hold weather information

Set up a configuration variable for the city to look up

Write a function that simulates a REST API call to get weather data for the city

Print the weather information for the chosen city

💡 Why This Matters

🌍 Real World

REST APIs are used everywhere to let apps and websites talk to servers and get data like weather, news, or user info.

💼 Career

Understanding REST APIs is key for software developers, web developers, and anyone working with modern apps that need to share data.

1

Create the weather data dictionary

Create a dictionary called weather_data with these exact entries: 'New York': 'Sunny', 'London': 'Cloudy', 'Tokyo': 'Rainy'

Rest API

# Create the weather_data dictionary with city names and weather
# Your code here

Hint

Use curly braces to create a dictionary with city names as keys and weather descriptions as values.

2

Set the city to look up

Create a variable called city and set it to the string 'London'

Rest API

weather_data = {'New York': 'Sunny', 'London': 'Cloudy', 'Tokyo': 'Rainy'}
# Set the city variable to 'London'
# Your code here

Hint

Assign the string 'London' to the variable city.

3

Write a function to simulate a REST API call

Define a function called get_weather that takes a parameter city_name and returns the weather from weather_data for that city using weather_data.get(city_name, 'No data')

Rest API

weather_data = {'New York': 'Sunny', 'London': 'Cloudy', 'Tokyo': 'Rainy'}
city = 'London'
# Define get_weather(city_name) function
# Your code here

Hint

Use the dictionary's get method to safely get the weather or return 'No data' if the city is not found.

4

Print the weather for the chosen city

Write a print statement that shows the text "Weather in {city}: {weather}" where weather is the result of calling get_weather(city)

Rest API

weather_data = {'New York': 'Sunny', 'London': 'Cloudy', 'Tokyo': 'Rainy'}
city = 'London'
def get_weather(city_name):
    return weather_data.get(city_name, 'No data')
# Print the weather for the city
# Your code here

Hint

Call get_weather with city and use an f-string to print the message.

Practice

1. Why do REST APIs exist in software development?

easy

A. To allow different programs to communicate over the internet using simple rules

B. To create complex user interfaces for websites

C. To store data only on local machines

D. To replace all programming languages with one standard

Solution

1. Step 1: Understand the purpose of REST APIs

   REST APIs are designed to let different software programs talk to each other over the internet easily.

2. Step 2: Compare options with this purpose

   Only To allow different programs to communicate over the internet using simple rules correctly describes this purpose. Options A, B, and C do not relate to REST APIs' main goal.

3. Final Answer:

   To allow different programs to communicate over the internet using simple rules -> Option A

4. Quick Check:

   REST APIs exist for communication = D [OK]

Hint: REST APIs help programs talk over the internet simply [OK]

Common Mistakes:

• Thinking REST APIs create user interfaces
• Believing REST APIs store data locally only
• Assuming REST APIs replace programming languages

2. Which HTTP method is commonly used in REST APIs to retrieve data from a server?

easy

A. GET

B. POST

C. DELETE

D. PUT

Solution

1. Step 1: Recall HTTP methods in REST APIs

   GET is the method used to request and retrieve data from a server.

2. Step 2: Match the method to the action

   POST sends data, DELETE removes data, PUT updates data. Only GET retrieves data.

3. Final Answer:

   GET -> Option A

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET means get data from server in REST APIs [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE or PUT to get data
• Not knowing HTTP method purposes

3. What will be the output of this REST API call?

GET /users/123

Assuming user 123 exists and the API returns JSON data.

medium

A. 500 Internal Server Error

B. {"id":123,"name":"Alice"}

C. 404 Not Found

D. {"error":"User not found"}

Solution

1. Step 1: Understand the GET request to /users/123

   This request asks the server for data about user with ID 123.

2. Step 2: Check the condition given

   The user 123 exists, so the server returns the user's data in JSON format.

3. Final Answer:

   {"id":123,"name":"Alice"} -> Option B

4. Quick Check:

   Existing user GET returns data = C [OK]

Hint: GET existing user returns JSON data, not error [OK]

Common Mistakes:

• Choosing error responses when user exists
• Confusing 404 with successful data return
• Not recognizing JSON format

4. Identify the error in this REST API usage:

POST /users/123

What is wrong if the goal is to update user 123's data?

medium

A. The URL should not include the user ID

B. GET method should be used to update data

C. POST is used instead of PUT for updating existing data

D. DELETE method is required to update data

Solution

1. Step 1: Understand HTTP methods for REST APIs

   POST is usually for creating new data, PUT is for updating existing data.

2. Step 2: Match method to action

   Since the goal is to update user 123, PUT should be used instead of POST.

3. Final Answer:

   POST is used instead of PUT for updating existing data -> Option C

4. Quick Check:

   Update needs PUT, not POST = B [OK]

Hint: Use PUT to update existing data, not POST [OK]

Common Mistakes:

• Using POST to update instead of PUT
• Thinking GET updates data
• Believing DELETE updates data

5. You want to design a REST API that allows clients to list all products and add new products. Which HTTP methods and URLs should you use?

hard

A. DELETE /products to list, PUT /products to add new

B. POST /products to list, GET /products to add new

C. PUT /products to list, DELETE /products to add new

D. GET /products to list, POST /products to add new

Solution

1. Step 1: Identify methods for listing and adding

   GET is used to retrieve or list data, POST is used to create or add new data.

2. Step 2: Match methods with URLs

   Both actions use the /products URL; GET lists products, POST adds new products.

3. Final Answer:

   GET /products to list, POST /products to add new -> Option D

4. Quick Check:

   List = GET, Add = POST = A [OK]

Hint: GET lists, POST adds new resources in REST APIs [OK]

Common Mistakes:

• Swapping GET and POST roles
• Using DELETE or PUT incorrectly
• Confusing URLs for different actions