python：对我的复制变量的更改会影响原始变量
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python: changes to my copy variable affect the original variable
提问by natsuki_2002
I've got a list that I create a copy of in order to do some manipulations while still keeping the original list. However, when I set copy_listequal to org_list, they become the same thing, and if I change copy_list, org_listchanges too. For example:
我有一个列表，我创建了一个副本，以便在保留原始列表的同时进行一些操作。但是，当我设置为copy_listequal 时org_list，它们变成了相同的东西，如果我改变了copy_list，org_list也会改变。例如：
org_list = ['y', 'c', 'gdp', 'cap']
copy_list = org_list
copy_list.append('hum')
print(copy_list)
print(org_list)
returns
返回
['y', 'c', 'gdp', 'cap', 'hum']
['y', 'c', 'gdp', 'cap', 'hum']
I don't know too much about what is actually going on but it looks like org_listis actually passing itself to copy_listso that they are actually the same thing.
我对实际发生的事情不太了解，但看起来org_list实际上是在传递给自己，copy_list因此它们实际上是同一件事。
Is there a way to make an independent copy of org_list without doing something clumsy like:
有没有办法制作 org_list 的独立副本而不会做一些笨拙的事情，例如：
copy_list = []
for i in org_list:
copy_list.append(i)
I say this because I have the same problem with other types of variables, for example a pandas dataframe.
我这样说是因为我对其他类型的变量也有同样的问题，例如熊猫数据框。
采纳答案by yuvi
That is because in python setting a variable actually sets a reference to the variable. Almost every person learning python encounters this at some point. The solution is simply to copy the list:
那是因为在 python 设置变量中实际上设置了对变量的引用。几乎每个学习 Python 的人都会在某个时候遇到这个问题。解决方案是简单地复制列表：
copy_list = org_list[:]
回答by John La Rooy
This is just copying the reference
这只是复制参考
copy_list = org_list
you should use
你应该使用
copy_list = org_list[:] # make a slice that is the whole list
or
或者
copy_list = list(org_list)
回答by Andrew Jaffe
回答by Roberto
When you write
当你写
org_list = ['y', 'c', 'gdp', 'cap']
you create the list object, and give it the name "org_list".
您创建列表对象，并将其命名为“org_list”。
Then when you do
然后当你做
copy_list = org_list
you just mean, "the name copy_list refers to the same object as org_list does".
您的意思是，“名称 copy_list 指代与 org_list 相同的对象”。
If your list only contains immutable types, then you can create a copy by
如果您的列表仅包含不可变类型，那么您可以通过以下方式创建副本
copy_list = list(org_list)
But note that this is only valid if the list objects are immutable, because it creates a SHALLOW copy, i.e. the list is copied, but every element on the list is not duplicated.
但请注意，这仅在列表对象是不可变的情况下才有效，因为它创建了一个浅拷贝，即列表被复制，但列表中的每个元素都不会重复。
If you have i.e. a list of lists and want EVERYTHING to be duplicated, you need to perform a DEEP copy:
如果您有一个列表列表并希望复制所有内容，则需要执行深度复制：
import copy
org_list = ['y', 'c', ['gdp', 'rtd'], 'cap']
copy_list = copy.deepcopy(org_list)
