Blockchain use cases beyond crypto - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple blockchain block structure with a timestamp.

Blockchain / Solidity

block = {
    'timestamp': [1],
    'data': 'Sample data'
}

Drag options to blanks, or click blank then click option'

Atime.time()

Bdatetime.now()

Crandom.randint(1, 100)

D'2024-01-01'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a fixed string instead of a dynamic timestamp.

Using a random number instead of a timestamp.

The datetime.now() function provides the current timestamp for the block.

2fill in blank

medium

Complete the code to calculate the hash of a block's data using SHA-256.

Blockchain / Solidity

import hashlib

block_data = 'Transaction data'
hash_result = hashlib.[1](block_data.encode()).hexdigest()

Drag options to blanks, or click blank then click option'

Amd5

Bsha512

Csha1

Dsha256

Attempts:

3 left

💡 Hint

Common Mistakes

Using weaker hash functions like MD5 or SHA1.

Using a hash function not supported by hashlib.

The sha256 function from hashlib is used to create a secure hash for blockchain data.

3fill in blank

hard

Fix the error in the code to add a new transaction to the blockchain list.

Blockchain / Solidity

blockchain = []
new_transaction = {'sender': 'Alice', 'receiver': 'Bob', 'amount': 50}
blockchain.[1](new_transaction)

Drag options to blanks, or click blank then click option'

Aappend

Badd

Cextend

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using add which is for sets.

Using extend which expects an iterable.

The append method adds a single item to the end of a list, which is correct for adding a transaction.

4fill in blank

hard

Fill both blanks to filter transactions with amount greater than 100 and create a dictionary with sender as key.

Blockchain / Solidity

filtered = {tx['sender']: tx for tx in transactions if tx['amount'] [1] 100 and tx['receiver'] [2] 'Unknown'}

Drag options to blanks, or click blank then click option'

A>

B<

C!=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than instead of greater than.

Using equality instead of inequality for receiver check.

The code filters transactions where amount is greater than 100 and receiver is not 'Unknown'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps block IDs to their data if the block is verified.

Blockchain / Solidity

verified_blocks = {block[1]: block[2] for block in blocks if block[3] == True}

Drag options to blanks, or click blank then click option'

A['id']

B['data']

C['verified']

D['timestamp']

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong keys for dictionary mapping.

Checking the wrong field for verification.

The dictionary comprehension maps each block's ID to its data only if the block is verified.