python - 无法从任何类中的析构函数调用函数

Question

我想在一个类中使用 ConfigParser，它需要从析构函数中调用，但奇怪的事情发生了。

这是我的代码:

"""
function name is 
test  ok!
test1 failed!
test2 failed!
test3 failed!

test4
...  ok!

"""

def test3():
  pass

class Class1:
  def __del__(self):
    test3()

if __name__=="__main__":
  obj=Class1()

如果函数名为test1、test2或test3，将引发异常，我无法通过尝试除外。

回溯是:

E:\tc.py
Exception TypeError: "'NoneType' object is not callable" in <bound method Class1.__del__ of <__main__.Class1 instance at 0x00C18F58>> ignored

太奇怪了!你能在你的系统中测试它吗？还是我做错了什么？

Answer 1

对象被销毁的顺序是未定义的。这意味着当 obj.__del__() 被调用时——如果它被调用的话——test3() 可能已经被破坏也可能没有被破坏。

documentation中有一个带有警告的红框:

Warning Due to the precarious circumstances under which __del__() methods are invoked, exceptions that occur during their execution are ignored, and a warning is printed to sys.stderr instead. Also, when __del__() is invoked in response to a module being deleted (e.g., when execution of the program is done), other globals referenced by the __del__() method may already have been deleted or in the process of being torn down (e.g. the import machinery shutting down). For this reason, __del__() methods should do the absolute minimum needed to maintain external invariants. Starting with version 1.5, Python guarantees that globals whose name begins with a single underscore are deleted from their module before other globals are deleted; if no other references to such globals exist, this may help in assuring that imported modules are still available at the time when the __del__() method is called.

在 Python 中，几乎从不覆盖 __del__。您可能应该重新考虑您的设计。参见 How do I correctly clean up a Python object?