如何及早删除函数参数？ [英] How to delete a function argument early?

问题描述

我正在编写一个函数，该函数需要大量参数并且可以运行很长时间。它只需要一半的参数。如果没有更多引用，该函数是否可以删除该参数所指向的值？

I'm writing a function which takes a huge argument, and runs for a long time. It needs the argument only halfway. Is there a way for the function to delete the value pointed to by the argument if there are no more references to it?

我能够尽快将其删除函数返回，如下所示：

I was able to get it deleted as soon as the function returns, like this:

def f(m):
  print 'S1'
  m = None
  #__import__('gc').collect()  # Uncommenting this doesn't help.
  print 'S2'
class M(object):   
  def __del__(self):
    print '__del__'
f(M())

此打印：

S1
S2
__del__

我需要：

S1
__del__
S2

我也在尝试 def f（* args）：和 def f（** kwargs），但这并没有帮助，最后我仍然得到 __ del __ 。

I was also trying def f(*args): and def f(**kwargs), but it didn't help, I still get __del__ last.

请注意我的代码依赖于Python具有引用计数这一事实，并且 __ del __ 在对象的引用计数降至零时立即被调用。我希望函数参数的引用计数在函数中间降至零。

Please note that my code is relying on the fact that Python has reference counting, and __del__ gets called as soon as an object's reference count drops to zero. I want the reference count of a function argument drop to zero in the middle of a function. Is this possible?

请注意，我知道一种解决方法：传递参数列表：

Please note that I know of a workaround: passing a list of arguments:

def f(ms):
  print 'S1'
  del ms[:]
  print 'S2'
class M(object):   
  def __del__(self):
    print '__del__'
f([M()])

此打印：

S1
__del__
S2

是否可以在不更改API的情况下（例如在参数列表中引入）来实现早期删除？

Is there a way to get the early deletion without changing the API (e.g. introducing lists to the arguments)?

如果很难获得可在许多Python实现中使用的便携式解决方案，那么我需要在最新的CPython 2.7中可以使用的解决方案。

If it's hard to get a portable solution which works in many Python implementations, I need something which works in the most recent CPython 2.7. It doesn't have to be documented.

推荐答案

似乎无法在CPython 2.7中进行早期删除而不进行更改 f 函数的API。

It look like it's not possible to do the early deletion in CPython 2.7 without changing the API of the f function.

这篇关于如何及早删除函数参数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！