dict.clear（）和Python分配{}之间的区别 [英] Difference between dict.clear() and assigning {} in Python

问题描述

在python中，调用 clear（）并将 {} 分配给字典之间有区别吗？如果是，是什么？
示例：

In python, is there a difference between calling clear() and assigning {} to a dictionary? If yes, what is it? Example:

d = {"stuff":"things"}
d.clear()   #this way
d = {}      #vs this way

推荐答案

也指同一个字典，有很大的区别：

If you have another variable also referring to the same dictionary, there is a big difference:

>>> d = {"stuff": "things"}
>>> d2 = d
>>> d = {}
>>> d2
{'stuff': 'things'}
>>> d = {"stuff": "things"}
>>> d2 = d
>>> d.clear()
>>> d2
{}

这是因为分配 d = {} 创建一个新的空字典，并将其分配给 d 变量。这将留下 d2 ，指向旧字典，其中仍有项目。但是， d.clear（）清除与 d 和 d2 都指向。

This is because assigning d = {} creates a new, empty dictionary and assigns it to the d variable. This leaves d2 pointing at the old dictionary with items still in it. However, d.clear() clears the same dictionary that d and d2 both point at.

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