del所做的部分(来自Python语言参考):

删除名称将从本地或全局名称空间删除该名称的绑定

将None赋值给名称不会删除名称与名称空间的绑定。

(我想关于移除名称绑定是否真的有用可能会有一些争论，但这是另一个问题。)

除非重新初始化，否则Del将从当前作用域删除变量。将其设置为None将其保留在当前范围内。

a = "python string"        
print(a)
del a
print(a)
a = "new python string"
print(a)

输出:

python string
Traceback (most recent call last):
  File "testing.py", line 4, in <module>
    print(a)
NameError: name 'a' is not defined

Del删除变量及其所指向的对象的绑定。

>>> a = ['a', 'b', 'c']
>>> b = a
>>> del a
>>> b
['a', 'b', 'c']
>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined

我能想到的一个简单的用例是，如果你已经使用内置函数名作为变量，并且你想在它已经被你的变量名“覆盖”之后使用该函数。

t = ('a', "letter")
value, type = t
print(value, type)
del type
print(type(value))

输出:

a letter
<class 'str'>

Del经常出现在__init__.py文件中。任何在__init__.py文件中定义的全局变量都将自动“导出”(它将包含在from模块import *中)。避免这种情况的一种方法是定义__all__，但这可能会很混乱，并不是每个人都使用它。

例如，如果你在__init__.py中有这样的代码

import sys
if sys.version_info < (3,):
    print("Python 2 not supported")

然后您的模块将导出sys名称。你应该写

import sys
if sys.version_info < (3,):
    print("Python 2 not supported")

del sys

I think one of the reasons that del has its own syntax is that replacing it with a function might be hard in certain cases given it operates on the binding or variable and not the value it references. Thus if a function version of del were to be created a context would need to be passed in. del foo would need to become globals().remove('foo') or locals().remove('foo') which gets messy and less readable. Still I say getting rid of del would be good given its seemingly rare use. But removing language features/flaws can be painful. Maybe python 4 will remove it :)

还有一个小众用途: 在带有ROOT5或ROOT6的pyroot中，"del"可以用于删除引用不再存在的c++对象的python对象。这允许pyroot的动态查找找到同名的c++对象，并将其绑定到python名称。所以你可以有这样一个场景:

import ROOT as R
input_file = R.TFile('inputs/___my_file_name___.root')
tree = input_file.Get('r')
tree.Draw('hy>>hh(10,0,5)')
R.gPad.Close()
R.hy # shows that hy is still available. It can even be redrawn at this stage.
tree.Draw('hy>>hh(3,0,3)') # overwrites the C++ object in ROOT's namespace
R.hy # shows that R.hy is None, since the C++ object it pointed to is gone
del R.hy
R.hy # now finds the new C++ object

希望ROOT7的更健全的对象管理能够填补这个空缺。