班级中的怪异名单行为 [英] Weird list behavior in class

问题描述

我写了一个具有列表作为变量的类.我有一个添加到该列表的函数和一个输出该列表的函数.

I've written a class that has a list as a variable. I have a function that adds to that list and a function that outputs that list.

class MyClass:
    myList = []

    def addToList(self, myNumber):
        self.myList.append(myNumber)

    def outputList(self):
        for someNumber in self.myList:
            print someNumber

现在出于某些奇怪的原因，如果我声明了该类的两个单独的对象，则:

Now for some weird reason, if I declare two separate objects of the class:

ver1 = MyClass()
ver2 = MyClass()

，然后在ver1上调用addToList:

and then call addToList on ver1:

ver1.addToList(3)

，然后输出ver2的列表:

and then output ver2's list:

ver2.outputList()

我得到3作为版本2列表的输出！发生什么事了?

I get 3 as output for version 2's list! What is happening?

推荐答案

您的语法错误.您正在使用类静态变量.考虑一下:

Your syntax is wrong. You are using a class-static variable. Consider this:

class MyClass:
    myList = []    # Static variable

    def __init__(self):
        self.myRealList = []   # Member variable

myList实际上是MyClass定义的一部分，因此不仅可见于类名，而且可见于该类的所有实例:

myList is actually a part of the MyClass definition, and thus is visible not only by the class name, but all instances of that class as well:

c = MyClass()
c.myList = [1]
print MyClass.myList  # will print [1]

您需要在__init__构造函数中声明常规的成员变量".

You need to declare regular "member variables" in the __init__ constructor.

还不错，我从C/C ++/C#领域来到python，犯了同样的错误，一开始它也使我感到困惑.

Don't feel bad, I came to python from a C/C++/C# world, made this same mistake, and it confused me too at first.

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