Python构造函数和默认值 [英] Python constructor and default value

问题描述

以某种方式，在下面的Node类中，在所有Node实例之间共享 wordList 和 adjacencyList 变量。

Somehow, in the Node class below, the wordList and adjacencyList variable is shared between all instances of Node.

>>> class Node:
...     def __init__(self, wordList = [], adjacencyList = []):
...         self.wordList = wordList
...         self.adjacencyList = adjacencyList
... 
>>> a = Node()
>>> b = Node()
>>> a.wordList.append("hahaha")
>>> b.wordList
['hahaha']
>>> b.adjacencyList.append("hoho")
>>> a.adjacencyList
['hoho']

有什么方法可以继续使用构造函数参数的默认值（在这种情况下为空列表），但要同时获取 a 和 b wordList 和 adjacencyList 变量？

Is there any way I can keep using the default value (empty list in this case) for the constructor parameters but to get both a and b to have their own wordList and adjacencyList variables?

我正在使用python 3.1.2。

I am using python 3.1.2.

推荐答案

可变的默认参数通常不能满足您的要求。相反，请尝试以下操作：

Mutable default arguments don't generally do what you want. Instead, try this:

class Node:
     def __init__(self, wordList=None, adjacencyList=None):
        if wordList is None:
            self.wordList = []
        else:
             self.wordList = wordList 
        if adjacencyList is None:
            self.adjacencyList = []
        else:
             self.adjacencyList = adjacencyList 

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