Token refresh mechanism in Rest API - Mini Project: Build & Apply

Token Refresh Mechanism

📖 Scenario: You are building a simple REST API that uses tokens to allow users to access protected resources. Tokens expire after some time, so you need a way to refresh them without asking the user to log in again.

🎯 Goal: Create a token refresh mechanism that checks if the current token is expired and issues a new token if needed.

📋 What You'll Learn

Create a dictionary called tokens with user tokens and their expiry times

Create a variable called current_time representing the current time

Write a function called refresh_token that takes a user and refreshes the token if expired

Print the refreshed token or a message if the token is still valid

💡 Why This Matters

🌍 Real World

Token refresh mechanisms are used in apps and websites to keep users logged in securely without asking for passwords repeatedly.

💼 Career

Understanding token refresh is important for backend developers working on authentication and security in web services.

1

Create the initial tokens dictionary

Create a dictionary called tokens with these exact entries: 'alice': {'token': 'abc123', 'expiry': 100}, 'bob': {'token': 'def456', 'expiry': 200}, and 'carol': {'token': 'ghi789', 'expiry': 50}.

Rest API

# Create the tokens dictionary with user tokens and expiry times
# Your code here

Need a hint?

Use a dictionary with usernames as keys and another dictionary as values holding 'token' and 'expiry'.

2

Set the current time

Create a variable called current_time and set it to 120 to represent the current time.

Rest API

tokens = {
    'alice': {'token': 'abc123', 'expiry': 100},
    'bob': {'token': 'def456', 'expiry': 200},
    'carol': {'token': 'ghi789', 'expiry': 50}
}
# Set the current_time variable to 120
# Your code here

Need a hint?

Just assign the number 120 to the variable current_time.

3

Write the token refresh function

Write a function called refresh_token that takes a parameter user. Inside the function, check if tokens[user]['expiry'] is less than current_time. If yes, update tokens[user]['token'] to 'newtoken123' and tokens[user]['expiry'] to current_time + 100. Otherwise, do nothing.

Rest API

tokens = {
    'alice': {'token': 'abc123', 'expiry': 100},
    'bob': {'token': 'def456', 'expiry': 200},
    'carol': {'token': 'ghi789', 'expiry': 50}
}

current_time = 120

# Write the refresh_token function below
# Your code here

Need a hint?

Use an if statement to compare expiry with current_time and update the token and expiry if expired.

4

Print the refreshed token

Call refresh_token for the user 'alice'. Then print the string "Refreshed token for alice: " followed by tokens['alice']['token'].

Rest API

tokens = {
    'alice': {'token': 'abc123', 'expiry': 100},
    'bob': {'token': 'def456', 'expiry': 200},
    'carol': {'token': 'ghi789', 'expiry': 50}
}

current_time = 120

def refresh_token(user):
    if tokens[user]['expiry'] < current_time:
        tokens[user]['token'] = 'newtoken123'
        tokens[user]['expiry'] = current_time + 100

# Call refresh_token for 'alice' and print the refreshed token
# Your code here

Need a hint?

Call the function with 'alice' and print the message with the updated token.