Accounts (EOA vs contract accounts) in Blockchain / Solidity - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if an address is an Externally Owned Account (EOA).

Blockchain / Solidity

if len(address.code) == [1]:
    print("This is an EOA.")

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

A0

BNone

C1

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 for code length.

An EOA has no code, so its code length is 0.

2fill in blank

medium

Complete the code to send Ether from an EOA to another address.

Blockchain / Solidity

tx = {
    'from': sender,
    'to': receiver,
    'value': [1]
}

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

Aamount_in_wei

B'amount'

C0

D'0x0'

Attempts:

3 left

💡 Hint

Common Mistakes

Using string literals instead of numeric values.

The 'value' field must be the amount of Ether in wei to send.

3fill in blank

hard

Fix the error in the code that tries to call a contract function from an EOA.

Blockchain / Solidity

contract = web3.eth.contract(address=contract_address, abi=contract_abi)
result = contract.functions.[1]().call()

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

Atransfer

BmyFunction

CsendTransaction

DbalanceOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using generic or incorrect function names.

You must call the actual function name defined in the contract ABI.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps EOAs to their balances if balance is greater than 0.

Blockchain / Solidity

balances = {addr: [1] for addr in addresses if [2] > 0}

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

Aweb3.eth.get_balance(addr)

Baddr

Dbalance

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that are not defined.

Use web3.eth.get_balance(addr) to get the balance for each address and filter those with balance > 0.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps contract addresses to their code size if code size is greater than zero.

Blockchain / Solidity

contract_codes = {addr: len([1]) for addr in contract_addresses if len([2]) [3] 0}

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

Aweb3.eth.get_code(addr)

C>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality check instead of greater than.

Use web3.eth.get_code(addr) to get the contract code and check if its length is greater than zero.