如果更改其他变量，变量也会更改 [英] variable changes if I change a different variable

问题描述

每当我创建一个类的实例时，创建一个为第一个实例分配的变量，并在我的第一个变量更改的第二个变量上使用该类的属性。

Whenever I create an instance of a class, create a variable that's assigned that first instance, and use an attribute of the class on the second variable my first variable changes.

class number:
    def __init__(self, value):
        self.value = value
    def add(self):
        self.value = self.value + 1
a = number(10)
b = a
b.add()
a.value

为什么当我不使用 a.add（）时a.value给我11 ？

why does a.value give me 11 when I didn't use a.add()?

推荐答案

@ juanpa.arrivillaga为您的问题提供了很好的评论。我只想添加如何修复您的代码以执行您期望的操作：

@juanpa.arrivillaga provided good comments to your question. I just want to add how to fix your code to do what you expect it to do:

class number:
    def __init__(self, value):
        self.value = value
    def add(self):
        self.value = self.value + 1
a = number(10)
b = number(a.value) # create a new object with the same value as 'a'
b.add()
a.value

方法2：

Method 2:

import copy
class number:
    def __init__(self, value):
        self.value = value
    def add(self):
        self.value = self.value + 1
a = number(10)
b = copy.copy(a) # make a shallow copy of the object a 
# b = copy.deepcopy(a) # <-- that is what most people think of a "real" copy
b.add()
a.value

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