Human-readable error messages in Rest API - Mini Project: Build & Apply

Human-readable error messages

📖 Scenario: You are building a simple REST API that returns data about books. When something goes wrong, you want to send clear, easy-to-understand error messages to the user instead of confusing technical errors.

🎯 Goal: Create a small API simulation that returns human-readable error messages for common problems like missing data or invalid input.

📋 What You'll Learn

Create a dictionary called books with three book entries and their authors

Create a variable called requested_book with the name of the book to search

Write code to check if requested_book is in books and handle errors with clear messages

Print the result or the error message

💡 Why This Matters

🌍 Real World

APIs often need to tell users what went wrong in a way they can understand, instead of showing confusing technical errors.

💼 Career

Clear error messages improve user experience and are important for developers working on web services and APIs.

1

Create the books data

Create a dictionary called books with these exact entries: '1984': 'George Orwell', 'To Kill a Mockingbird': 'Harper Lee', 'The Great Gatsby': 'F. Scott Fitzgerald'

Rest API

# Create the books dictionary with exact entries
# Your code here

Hint

Use curly braces {} to create a dictionary with the exact book titles as keys and authors as values.

2

Set the requested book

Create a variable called requested_book and set it to the string 'The Catcher in the Rye'

Rest API

books = {
    '1984': 'George Orwell',
    'To Kill a Mockingbird': 'Harper Lee',
    'The Great Gatsby': 'F. Scott Fitzgerald'
}
# Set the requested_book variable to 'The Catcher in the Rye'
# Your code here

Hint

Assign the exact string 'The Catcher in the Rye' to the variable requested_book.

3

Check for the book and prepare error messages

Write an if statement to check if requested_book is in books. If it is, create a variable result with the message "Found: {requested_book} by {author}". If not, set result to the error message "Error: '{requested_book}' not found in the library."

Rest API

books = {
    '1984': 'George Orwell',
    'To Kill a Mockingbird': 'Harper Lee',
    'The Great Gatsby': 'F. Scott Fitzgerald'
}
requested_book = 'The Catcher in the Rye'
# Check if requested_book is in books and set result with a human-readable message
# Your code here

Hint

Use an if statement to check membership and f-strings to create clear messages.

4

Print the result

Write a print statement to display the variable result

Rest API

books = {
    '1984': 'George Orwell',
    'To Kill a Mockingbird': 'Harper Lee',
    'The Great Gatsby': 'F. Scott Fitzgerald'
}
requested_book = 'The Catcher in the Rye'

if requested_book in books:
    author = books[requested_book]
    result = f"Found: {requested_book} by {author}"
else:
    result = f"Error: '{requested_book}' not found in the library."

# Print the result variable
# Your code here

Hint

Use print(result) to show the message on the screen.

Practice

1.

What is the main purpose of human-readable error messages in a REST API?

easy

A. To confuse users with complex codes

B. To hide all error details from users

C. To make error messages as technical as possible

D. To explain problems in simple words for users

Solution

1. Step 1: Understand the role of error messages

   Error messages should help users understand what went wrong.

2. Step 2: Identify the best description

   Human-readable means simple and clear, not technical or confusing.

3. Final Answer:

   To explain problems in simple words for users -> Option D

4. Quick Check:

   Human-readable = simple explanation [OK]

Hint: Think: error messages should help, not confuse [OK]

Common Mistakes:

• Choosing technical jargon instead of simple words
• Assuming error messages should hide details
• Confusing human-readable with code-only messages

2.

Which of the following is the correct JSON format for a human-readable error message in a REST API response?

{
  "error": {
    "code": 404,
    "message": "Resource not found"
  }
}

easy

A. { error: 404, message: 'Not found' }

B. { "error": { "code": 404, "message": "Resource not found" } }

C. { "code": 404, "msg": "Not found" }

D. { error_code: 404, error_message: 'Resource missing' }

Solution

1. Step 1: Check JSON syntax correctness

   Valid JSON requires double quotes around keys and string values.

2. Step 2: Match the expected structure

   The error object should contain code and message keys with clear names.

3. Final Answer:

   { "error": { "code": 404, "message": "Resource not found" } } -> Option B

4. Quick Check:

   Valid JSON with clear keys = { "error": { "code": 404, "message": "Resource not found" } } [OK]

Hint: Look for double quotes and clear key names in JSON [OK]

Common Mistakes:

• Using single quotes instead of double quotes in JSON
• Missing nested error object structure
• Using incorrect key names like 'msg' or 'error_code'

3.

Given this API response code snippet, what will be the output message?

response = {
  "status": 400,
  "error": {
    "code": "INVALID_INPUT",
    "message": "Input value is not valid"
  }
}
print(response["error"]["message"])

medium

A. Input value is not valid

B. 400

C. INVALID_INPUT

D. KeyError

Solution

1. Step 1: Access nested dictionary keys

   response["error"] gives the nested dictionary, then ["message"] accesses the message string.

2. Step 2: Print the message value

   The value of response["error"]["message"] is "Input value is not valid".

3. Final Answer:

   Input value is not valid -> Option A

4. Quick Check:

   Nested key access = message string [OK]

Hint: Follow dictionary keys step-by-step to find the message [OK]

Common Mistakes:

• Printing the error code instead of message
• Confusing status code with error message
• Trying to access keys incorrectly causing KeyError

4.

Identify the error in this REST API error response JSON and fix it for proper human-readable message format:

{
  error: {
    code: 401,
    message: 'Unauthorized access'
  }
}

medium

A. Remove the error object and keep only code and message

B. Change code 401 to string '401'

C. Replace single quotes with double quotes and add quotes around keys

D. Add a status key with value 'error'

Solution

1. Step 1: Check JSON syntax rules

   JSON keys and string values must be in double quotes, not single quotes or unquoted.

2. Step 2: Fix the JSON format

   Add double quotes around keys (error, code, message) and change single quotes to double quotes.

3. Final Answer:

   Replace single quotes with double quotes and add quotes around keys -> Option C

4. Quick Check:

   Valid JSON needs double quotes on keys and strings [OK]

Hint: JSON keys and strings always need double quotes [OK]

Common Mistakes:

• Using single quotes for strings in JSON
• Leaving keys unquoted causing syntax errors
• Changing numeric codes to strings unnecessarily

5.

You want to design a REST API error response that helps users fix input errors quickly. Which approach is best?

{
  "error": {
    "code": "INVALID_EMAIL",
    "message": "Email format is incorrect",
    "field": "email",
    "suggestion": "Use a valid email like [e-mail]"
  }
}

hard

A. Include error code, message, field name, and suggestion for fix

B. Only include a generic error message without details

C. Return HTTP 200 status with error details inside

D. Send error details only in server logs, not in response

Solution

1. Step 1: Identify helpful error response elements

   Clear code, message, field, and suggestion guide users to fix errors.

2. Step 2: Compare options for user-friendliness

   Include error code, message, field name, and suggestion for fix provides detailed, human-readable info; others hide or confuse users.

3. Final Answer:

   Include error code, message, field name, and suggestion for fix -> Option A

4. Quick Check:

   Detailed, clear errors improve user experience [OK]

Hint: Add suggestions and field info for clearer error messages [OK]

Common Mistakes:

• Returning generic messages without guidance
• Using HTTP 200 for errors causing confusion
• Hiding error details from users