bchain.py

blockchain = []


def get_last_value():
    """ extracting the last element of the blockchain list """
    return blockchain[-1]


def add_value(transaction_amount, last_transaction=None):
    if last_transaction is None:
        last_transaction = [1]
    blockchain.append([last_transaction, transaction_amount])


def get_transaction_value():
    user_value = float(input('Enter your transaction amount '))
    return user_value


def get_user_choice():
    user_input = input("Please give your choice here: ")
    return user_input


def print_block():
    for block in blockchain:
        print("Here is your block")
        print(block)


def verify_chain():
    index = 0
    valid = True
    for block in blockchain:
        if index == 0:
            index += 1
            continue
        elif block[0] == blockchain[index - 1]:
            valid = True
        else:
            valid = False
            break
        index += 1
    return valid


tx_amount = get_transaction_value()
add_value(tx_amount)

while True:
    print("Choose an option")
    print('Choose 1 for adding a new transaction')
    print('Choose 2 for printing the blockchain')
    print('Choose 3 if you want to manipulate the data')
    print('Choose anything else if you want to quit')
    user_choice = get_user_choice()
    if user_choice == 1:
        tx_amount = get_transaction_value()
        add_value(tx_amount, get_last_value())
    elif user_choice == 2:
        print_block()
    elif user_choice == 3:
        if len(blockchain) >= 1:
            blockchain[0] = 2
    else:
        break
    if not verify_chain():
        print('Block-Chain manipulated')
        break