更新嵌套字典中的值-Python

问题描述：

我创建了一个字典，如下所示:

I created a dictionary as follows:

gP = dict.fromkeys(range(6), {'a': None, 'b': None, 'c': None, 'd': None})

现在，当我尝试修改值时:

Now, when I try to modify a value doing:

gP[0]['a'] = 1

由于某些原因，a的所有值(无论它们属于哪个键)都变为1，如下所示:

for some reason, all the values of a (regardless of the key they belong to) change to 1 as shown below:

{0: {'a': 1, 'b': None, 'c': None, 'd': None},
 1: {'a': 1, 'b': None, 'c': None, 'd': None},
 2: {'a': 1, 'b': None, 'c': None, 'd': None},
 3: {'a': 1, 'b': None, 'c': None, 'd': None},
 4: {'a': 1, 'b': None, 'c': None, 'd': None},
 5: {'a': 1, 'b': None, 'c': None, 'd': None}}

我做错了什么?正确的赋值声明是什么?

What I am doing wrong? What's the proper assignment statement?

答

正如@deceze所说，Python不会复制.您在键值对的所有值部分中引用的是同一个字典.

As @deceze said, Python doesn't make copies. You are referencing the same dict in all the value parts of the key-value pairs.

一种替代方法是:

gP = {x: {'a': None, 'b': None, 'c': None, 'd': None} for x in range(6)}

更新: @Chris_Rands 有一个更干净的答案版本:

Update: There is a much cleaner version of this answer by @Chris_Rands:

{x: dict.fromkeys('abcd') for x in range(6)}

更新嵌套字典中的值-Python

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