如何复制字典并仅编辑副本 [英] How to copy a dictionary and only edit the copy

问题描述

有人可以向我解释一下吗?这对我来说没有任何意义.

我将一本字典复制到另一个字典中并编辑第二个，两者都发生了变化.为什么会发生这种情况?

<预><代码>>>>dict1 = {"key1": "value1", "key2": "value2"}>>>字典 2 = 字典 1>>>字典2{'key2':'value2'，'key1':'value1'}>>>dict2["key2"] = "为什么?！">>>字典1{'key2':'为什么?！'，'key1':'value1'}

解决方案

Python never 隐式复制对象.当您设置 dict2 = dict1 时，您是在使它们引用完全相同的 dict 对象，因此当您对其进行变异时，对它的所有引用都会继续引用处于当前状态的对象.

如果你想复制字典(这种情况很少见)，你必须明确地使用

dict2 = dict(dict1)

或

dict2 = dict1.copy()

Can someone please explain this to me? This doesn't make any sense to me.

I copy a dictionary into another and edit the second and both are changed. Why is this happening?

>>> dict1 = {"key1": "value1", "key2": "value2"}
>>> dict2 = dict1
>>> dict2
{'key2': 'value2', 'key1': 'value1'}
>>> dict2["key2"] = "WHY?!"
>>> dict1
{'key2': 'WHY?!', 'key1': 'value1'}

解决方案

Python never implicitly copies objects. When you set dict2 = dict1, you are making them refer to the same exact dict object, so when you mutate it, all references to it keep referring to the object in its current state.

If you want to copy the dict (which is rare), you have to do so explicitly with

dict2 = dict(dict1)

or

dict2 = dict1.copy()

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