Python 为什么在我返回项目时不显示它？我得到的是记忆的位置

基本上，我要做的是显示支出列表中属于同一类别的所有项目，然后显示每个类别的总额，最后显示总总额。例如：

$12.00 Mon, 12 Aug 2019 Food
$15.25 Mon, 12 Aug 2019 Food
Total for Food = $27.25
$8.40 Wed, 14 Aug 2019 Drinks
Total for Drinks = $8.40
$33.00 Tue, 13 Aug 2019 Entertainment
Total for Entertainment = $33.00
Overall Total = $178.55

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根据之前的评论进行了一些更改

您的问题是这两行（加上其他几个点）：

导致错误的最小示例：

exp = {}
exp['test'] = []
# exp = {'test': []}
exp['test']['Amount'] = [] # Amount throws an error because exp['test'] is a list.

我想你的意思是：

exp[types] = {}
exp[types]['Amount'] = []

但你的另一个逻辑令人困惑：

# Here you assume exp[item._type] is of type list because you use append on it
exp[item._type].append(item)

# But here you assume exp[item._type] is of type dict because you call ['Amount'] on it...
exp[item._type]['Amount'].append(item._amount)

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请粘贴错误回溯，它准确地告诉您是哪一行导致了问题，以及导致问题的那几行。

\uuuu str\uuuu（）

不应该打印任何内容，它的工作是返回对象的字符串版本（调用者可以选择打印，也可以选择完全执行其他操作）。

exp[types] = {}
exp[types]['Amount'] = []

# Here you assume exp[item._type] is of type list because you use append on it
exp[item._type].append(item)

# But here you assume exp[item._type] is of type dict because you call ['Amount'] on it...
exp[item._type]['Amount'].append(item._amount)