python - 如何复制字典并仅编辑副本(How to copy a dictionary and only edit the copy)

Question

Can someone please explain this to me?

(有人可以向我解释一下吗？)

This doesn't make any sense to me.

(这对我来说毫无意义。)

I copy a dictionary into another and edit the second and both are changed.

(我将字典复制到另一个字典中，然后编辑第二个字典，并且两者都已更改。)

Why is this happening?

(为什么会这样呢？)

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

  ask by MadSc13ntist translate from so

Answer 1

Python never implicitly copies objects.

(Python 绝不会隐式复制对象。)

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.

(设置dict2 = dict1 ， dict2 = dict1它们引用相同的确切dict对象，因此，在对它进行突变时，对其的所有引用将始终引用该对象的当前状态。)

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

(如果要复制字典（这种情况很少见），则必须使用)

dict2 = dict(dict1)

or

(要么)

dict2 = dict1.copy()