如何将值附加到 dict 键?(AttributeError:'str'对象没有属性'append')

How do I append a value to dict key? (AttributeError: #39;str#39; object has no attribute #39;append#39;)(如何将值附加到 dict 键?(AttributeError:str对象没有属性append))

问题描述

假设我有一本带有一个键(和一个值)的字典:

Say I have a dictionary with one key (and a value):

dict = {'key': '500'}.

现在我想向同一个键添加一个新值 '1000'.然而，

Now I want to add a new value '1000' to the same key. However,

dict[key].append('1000')

只给我 AttributeError: 'str' object has no attribute 'append'".

如果我这样做了

dict[key] = '1000' 

它替换了之前的值.

我猜我必须创建一个列表作为值，并以某种方式将该列表附加为键的值，但我不确定我将如何处理.感谢您的帮助！

I'm guessing I have to create a list as a value and somehow append that list as the key's value but I'm not sure how I would go about this. Thanks for any help!

推荐答案

我建议使用 defaultdict 在缺少键时实例化一个空列表.

I suggest the usage of a defaultdict that instantiates an empty list when a key is missing.

>>> from collections import defaultdict
>>> d = defaultdict(list)
>>> d['key'].append(500)
>>> d
defaultdict(<type 'list'>, {'key': [500]})
>>> d['key'].append(1000)
>>> d
defaultdict(<type 'list'>, {'key': [500, 1000]})

我不建议将字符串/整数作为值，然后在您想附加到字段时切换到列表.保持一致.

I don't recommend having strings/integers as values and then switching to lists once you want to append to a field. Keep it consistent.

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