Why handling value is core to blockchain - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple transaction object with a value field.

Blockchain / Solidity

transaction = {"sender": "Alice", "receiver": "Bob", "[1]": 50}

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

Avalue

Bhash

Ctimestamp

Dnonce

Attempts:

3 left

💡 Hint

Common Mistakes

Using keys like 'hash' or 'nonce' instead of 'value' for the amount.

The key value represents the amount being transferred, which is essential in blockchain transactions.

2fill in blank

medium

Complete the code to add the transaction value to the sender's balance check.

Blockchain / Solidity

if sender_balance >= [1]:
    print("Transaction approved")

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

Atransaction['hash']

Btransaction['value']

Ctransaction['timestamp']

Dtransaction['nonce']

Attempts:

3 left

💡 Hint

Common Mistakes

Checking against 'hash' or 'nonce' which are unrelated to the amount.

The sender must have enough value to cover the transaction amount.

3fill in blank

hard

Fix the error in the code to correctly update the receiver's balance by adding the transaction value.

Blockchain / Solidity

receiver_balance = receiver_balance [1] transaction['value']

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

A+

B*

C/

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

To increase the receiver's balance, you add the transaction value.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each user to their transaction value if the value is greater than 10.

Blockchain / Solidity

{user: [1] for user, [2] in transactions.items() if [1] > 10}

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

Avalue

Bamount

Cval

Dbalance

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keys like 'amount' or 'val' which may not exist.

The dictionary comprehension uses the key value from each transaction to filter and map users.

5fill in blank

hard

Fill all three blanks to create a filtered dictionary of users with transaction values above 100, using uppercase usernames as keys.

Blockchain / Solidity

filtered = {user.[1](): [2] for user, [3] in transactions.items() if [2] > 100}

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

Alower

Bvalue

Ctransaction_value

Dupper

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'lower' instead of 'upper' or wrong keys for transaction amounts.

Usernames are converted to uppercase with upper(), and the transaction value is used for filtering and mapping.