反转具有单个元素的列表给出无 [英] Reversing a list with single element gives None

问题描述

当我从函数返回一个列表(带有单个元素)然后尝试使用 reverse() 反转它时，我注意到了奇怪的行为

I noticed odd behaviour when returning a list (with a single element) from a function and then trying to reverse it, using reverse()

我在这里提炼过:

def myFunction():
  return ["The Smiths"]

nums = [5,4,3,2,1]
nums.reverse()
print nums # 1,2,3,4,5 - fine!

# lets use one element in a list
something = ["Gwen Stefani"]
something.reverse()
print something # ["Gwen Stefani"] also fine

# now let's do the same, but from a function
a = myFunction()
print a # The Smiths
print a.reverse() # None
print a[::-1] # The Smiths

我需要一个大人来解释创建 None 而不是 [::-1] 中看到的单个元素是怎么回事.

I need a grown-up to explain what is going on to create the None instead of the single element as seen with [::-1].

推荐答案

list.reverse() 就地反转列表，但函数本身不返回任何内容.

list.reverse() reverses the list in-place, but the function itself doesn't return anything.

a = ["The Smiths"]
print a # The Smiths
print a.reverse() # None
print a # It's already there

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