python - 如何修复在线课程代码中的这个 json.dumps 错误？

Question

我正在学习 Python，我正在学习 Udemy 课程，但课程代码给了我错误：blockchain = json.loads(file_content[0][:-1]) IndexError: list index out of range

我不明白这一切，我不确定我应该做什么。在我添加 json.dumps 之前，整个代码都运行良好，现在在完成本节之前我无法继续上课。

讲师版本的代码运行同样的错误。这是整个代码：

from functools import reduce
import hashlib as hl
from collections import OrderedDict
import json

from hash_util import hash_string_256, hash_block

# intializing blockchain
MINING_REWARD = 10

genesis_block = {
        'previous_hash': '', 
        'index':0, 
        'transactions': [],
        'proof': 100
    }
blockchain = [genesis_block]
open_transactions = []
owner = 'Max'
participants = {'Max'}

def load_data():
        with open('Blockchain.txt', mode='r') as f:
            file_content = f.readlines()
            global blockchain
            global open_transactions
            blockchain = json.loads(file_content[0][:-1])
            open_transactions = json.loads(file_content[1])

load_data()

def save_data():
    with open('Blockchain.txt', mode='w') as f:
        f.write(json.dumps(blockchain))
        f.write('\n')
        f.write(json.dumps(open_transactions))

def valid_proof(transactions, last_hash, proof):
    guess = (str(transactions) + str(last_hash)+ str(proof)).encode()
    guess_hash = hash_string_256(guess)
    print(guess_hash)
    return guess_hash[0:2] == '00'

def proof_of_work():
    last_block = blockchain[-1]
    last_hash = hash_block(last_block)
    proof = 0
    while not valid_proof(open_transactions, last_hash, proof):
        proof += 1
    return proof

def get_balance(participant):
    tx_sender = [[tx['amount'] for tx in block['transactions'] if tx['sender'] == participant] for block in blockchain]
    open_tx_sender = [tx['amount'] for tx in open_transactions if tx['sender'] == participant]
    tx_sender.append(open_tx_sender)
    amount_sent = reduce(lambda tx_sum, tx_amt: tx_sum + sum(tx_amt) if len(tx_amt) > 0 else tx_sum + 0, tx_sender, 0)
    tx_recipient = [[tx['amount'] for tx in block['transactions'] if tx['recipient'] == participant] for block in blockchain]
    amount_received = reduce(lambda tx_sum, tx_amt: tx_sum + sum(tx_amt) if len(tx_amt) > 0 else tx_sum + 0, tx_recipient, 0)
    return amount_received - amount_sent

def get_last_blockchain_value():
    if len(blockchain) < 1:
        return None
    return blockchain[-1]

def verify_transaction(transaction):
    sender_balance = get_balance(transaction['sender'])
    return sender_balance >= transaction['amount']

def add_transaction(recipient, sender=owner, amount = 1.0):
    transaction = OrderedDict([('sender', sender), ('recipient', recipient), ('amount', amount)])
    if verify_transaction(transaction):
        open_transactions.append(transaction)
        participants.add(sender)
        participants.add(recipient)
        save_data()
        return True
    return False

def mine_block():
    last_block = blockchain[-1]
    hashed_block = hash_block(last_block)
    proof = proof_of_work()
    reward_transaction = OrderedDict([('sender', 'MINING'), ('recipient', owner), ('amount', MINING_REWARD)])
    copied_transactions = open_transactions[:]
    copied_transactions.append(reward_transaction)
    block = {
        'previous_hash': hashed_block, 
        'index':len(blockchain), 
        'transactions': copied_transactions,
        'proof': proof
    }
    blockchain.append(block)
    save_data()
    return True

def get_transaction_value():
    tx_recipient = input('Enter the recipient of the transaction: ')
    tx_amount =  float(input('Your transaction amount please: '))
    return(tx_recipient, tx_amount)

def get_user_choice():
    user_input = input('Your choice: ')
    return user_input

def print_blockchain_elements():
    for block in blockchain:
        print('Outputting block')
        print(block)
    else:
        print('-' * 20)

def verify_chain():
    for (index,block) in enumerate(blockchain):
        if index == 0:
            continue
        if block['previous_hash'] != hash_block(blockchain[index - 1]):
            return False
        if not valid_proof(block['transactions'][:-1], block['previous_hash'], block['proof']):
            print('Proof of work is invalid')
            return False
    return True

def verify_transactions():
    return all([verify_transactions(tx) for tx in open_transactions])

waiting_for_input = True


while waiting_for_input:
    print('please choose:')
    print('1: Add a new value')
    print('2: Mine a new block')
    print('3: Output the blocks')
    print('4: Output the participants')
    print('5: Check transaction validity')
    print('h: Manipulate the chain')
    print('q: Quit')
    user_choice = get_user_choice()
    if user_choice == '1':
        tx_data = get_transaction_value()
        recipient, amount = tx_data
        if add_transaction(recipient, amount=amount):
            print('Added transaction!')
        else:
            print('Transaction failed!')
        print(open_transactions)
    elif user_choice == '2':
        if mine_block():
            open_transactions = []
    elif user_choice == '3':
        print_blockchain_elements()
    elif user_choice == '4':
        print(participants)
    elif user_choice == '5':
        if verify_transactions():
            print('All transactions are valid')
        else:
            print('There are invalid transactions')
    elif user_choice == 'h':
        if len(blockchain) >= 1:
            blockchain[0] = {
            'previous_hash': '', 
            'index':0, 
            'transactions': [{'sender':'Chris','recipient':'Max','amount':100.0}]
        }
    elif user_choice == 'q':
        waiting_for_input = False
    else:
        print('Input was invalid, please choose from the list!')
    if not verify_chain():
        print_blockchain_elements()
        print('Invalid blockchain!')
        break 
    print('Balance of {}: {:6.2f}'.format('Max', get_balance('Max')))
else:
    print('User Left!')

print('Done!')

标签： pythonjson