清除清单的不同方法 [英] Different ways of clearing lists

问题描述

当您想在Python中清除列表时，有什么理由要做比这两行之一更复杂的事情吗?

Is there any reason to do anything more complicated than one of these two lines when you want to clear a list in Python?

old_list = []
old_list = list()

我问的原因是我只是在一些正在运行的代码中看到了这一点:

The reason I ask is that I just saw this in some running code:

del old_list[ 0:len(old_list) ]

推荐答案

清除列表将影响同一列表的所有其他引用.

Clearing a list in place will affect all other references of the same list.

例如，此方法不会影响其他引用:

For example, this method doesn't affect other references:

>>> a = [1, 2, 3]
>>> b = a
>>> a = []
>>> print(a)
[]
>>> print(b)
[1, 2, 3]

但是这个确实做到了:

>>> a = [1, 2, 3]
>>> b = a
>>> del a[:]      # equivalent to   del a[0:len(a)]
>>> print(a)
[]
>>> print(b)
[]
>>> a is b
True

您也可以这样做:

>>> a[:] = []

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