如何使用python中的函数对列表进行突变? [英] How to mutate a list with a function in python?

问题描述

这是我写的描述我的问题的伪代码:-

Here's a pseudocode I've written describing my problem:-

func(s):
   #returns a value of s

x = a list of strings
print func(x)
print x #these two should give the SAME output

当我最后打印x的值时，我希望它是func(x)返回的值.我只能通过编辑功能(而不设置x = func(x))

When I print the value of x in the end, I want it to be the one returned by func(x). Can I do something like this only by editing the function (and without setting x = func(x))

推荐答案

func(s):
   s[:] = whatever after mutating
   return s

x = a list of strings
print func(x)
print x

您实际上不需要返回任何内容:

You don't actually need to return anything:

def func(s):
    s[:] = [1,2,3]

x = [1,2]
print func(x)
print x # -> [1,2,3]

这完全取决于您的实际操作，在您实际更改传入的原始对象/列表时，追加或列表的任何直接突变都将反映在函数外部.如果您正在做的事情创建了一个新对象并且您希望反映在设置s[:] =..中传递的列表中的更改将更改原始列表.

It all depends on what you are actually doing, appending or any direct mutation of the list will be reflected outside the function as you are actually changing the original object/list passed in. If you were doing something that created a new object and you wanted the changes reflected in the list passed in setting s[:] =.. will change the original list.

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