Using for directive in Blockchain / Solidity - Mini Project: Build & Apply

Using for directive in blockchain smart contract

📖 Scenario: You are creating a simple blockchain smart contract that manages a list of registered users. You want to loop through the list of users to check their status.

🎯 Goal: Build a smart contract that stores a list of users and uses a for directive to iterate over them to count how many are active.

📋 What You'll Learn

Create a list variable called users with exact entries: 'Alice', 'Bob', 'Charlie'

Create a dictionary called status with exact entries: 'Alice': True, 'Bob': False, 'Charlie': True

Use a for directive with variable user to iterate over users

Count how many users have True status in status

Print the count with the exact text: Active users: X where X is the count

💡 Why This Matters

🌍 Real World

Smart contracts often need to process lists of users or transactions. Using loops helps automate checks and calculations.

💼 Career

Blockchain developers use loops and data structures to manage user states, balances, and permissions efficiently in smart contracts.

1

Create the list of users

Create a list called users with these exact entries: 'Alice', 'Bob', 'Charlie'

Blockchain / Solidity

# Create the list of users
# Your code here

Need a hint?

Use square brackets [] to create a list and separate names with commas.

2

Create the status dictionary

Create a dictionary called status with these exact entries: 'Alice': True, 'Bob': False, 'Charlie': True

Blockchain / Solidity

users = ['Alice', 'Bob', 'Charlie']
# Create the status dictionary
# Your code here

Need a hint?

Use curly braces {} to create a dictionary with keys and boolean values.

3

Use for directive to count active users

Create a variable called active_count and set it to 0. Then use a for directive with variable user to iterate over users. Inside the loop, increase active_count by 1 if status[user] is True.

Blockchain / Solidity

users = ['Alice', 'Bob', 'Charlie']
status = {'Alice': True, 'Bob': False, 'Charlie': True}
# Count active users using for directive
# Your code here

Need a hint?

Use for user in users: to loop, and check if status[user]: to count active users.

4

Print the number of active users

Write a print statement to display the text Active users: X where X is the value of active_count.

Blockchain / Solidity

users = ['Alice', 'Bob', 'Charlie']
status = {'Alice': True, 'Bob': False, 'Charlie': True}
active_count = 0
for user in users:
    if status[user]:
        active_count += 1
# Print the active user count
# Your code here

Need a hint?

Use print(f"Active users: {active_count}") to show the result.