Python将空列表更改为整数

Question

所以我的问题是编写一个function statement（），它将一系列浮点数作为输入，正数表示银行帐户的存款，负数表示从银行帐户中取款。您的函数应该返回两个浮点数的列表；第一个是存款的总和，第二个（负数）是取款的总和。在

我写的那个似乎是把取款空列表改为0，这样就不允许append函数工作了。我想知道python这样做是有原因的，还是仅仅是一个奇怪的错误？在

以下代码供参考：

def statement(lst):
"""returns a list of two numbers; the first is the sum of the
   positive numbers (deposits) in list lst, and the second is
   the sum of the negative numbers (withdrawals)"""
deposits, withdrawals, final = [], [], []
for l in lst:
    print(l)
    if l < 0:
        print('the withdrawals are ', withdrawals)  # test
        withdrawals.append(l)
        print('the withdrawals are ', withdrawals)  # test
    else:
        print('the deposits are', deposits)  # test
        deposits.append(l)
        print('the deposits are', deposits)  # test
    withdrawals = sum(withdrawals)
    deposits = sum(deposits)
    final.append(deposits)
    final.append(withdrawals)

Answer 1

这些线条：

withdrawals = sum(withdrawals)
deposits = sum(deposits)
final.append(deposits)
final.append(withdrawals)

需要写为：

^{pr2}$

否则，变量withdrawals和deposits将反弹到sum返回的整数对象。换句话说，它们将不再引用此处创建的列表对象：

deposits, withdrawals, final = [], [], []