从字典中删除一个元素 [英] Delete an element from a dictionary

问题描述

有没有办法在 Python 中从字典中删除项目?

Is there a way to delete an item from a dictionary in Python?

另外，如何从字典中删除一个项目以返回副本(即不修改原始项目)?

Additionally, how can I delete an item from a dictionary to return a copy (i.e., not modifying the original)?

推荐答案

del 语句 删除一个元素:

The del statement removes an element:

del d[key]

请注意，这会改变现有字典，因此对于引用同一实例的任何其他人，字典的内容都会更改.要返回新字典，请复制字典:

Note that this mutates the existing dictionary, so the contents of the dictionary changes for anybody else who has a reference to the same instance. To return a new dictionary, make a copy of the dictionary:

def removekey(d, key):
    r = dict(d)
    del r[key]
    return r

dict() 构造函数创建一个浅拷贝.要进行深层复制，请参阅copy 模块.

The dict() constructor makes a shallow copy. To make a deep copy, see the copy module.

请注意，为每个 dict del/assignment/etc 制作一个副本.意味着您将从恒定时间变为线性时间，并且还使用线性空间.对于小字典，这不是问题.但是，如果您打算制作大量大型字典的副本，您可能需要不同的数据结构，例如 HAMT(如 中所述)这个答案).

Note that making a copy for every dict del/assignment/etc. means you're going from constant time to linear time, and also using linear space. For small dicts, this is not a problem. But if you're planning to make lots of copies of large dicts, you probably want a different data structure, like a HAMT (as described in this answer).

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