python是不是以错误的顺序从swip中删除实例？可以修改吗？

Posted 2023-02-23

【中文标题】python是不是以错误的顺序从swip中删除实例？可以修改吗？

【英文标题】：does python delete instances from swip in wrong order? Can it be modified?python是否以错误的顺序从swip中删除实例？可以修改吗？

【发布时间】：2017-02-14 14:42:14

【问题描述】：

我使用 SWIG 在 c++ 中封装了一些类。我的 python 脚本看起来像

#!/usr/bin/python
import pyinput
import pygeom
import pystate
import pyeqfactory
import pyeigenprobfactory
import pyeigensolver

inp = pyinput.Input("heter1d/1d1g_heter")
geo = pygeom.ProbGeom1D(inp)
state = pystate.State1D(inp, geo);
equation = pyeqfactory.EqFactory1D.New(state)
eigenprob = pyeigenprobfactory.EigenProbFactory1D.New(state, equation)
solver = pyeigensolver.EigenSolver1D(state, eigenprob)
solver.solve_eigenproblem()
print state.get_keff()

我从智能指针类中得到一个错误，因为一个实例在被其他人拥有的同时被删除了

--------------------------------------------------------
An error occurred in line <114> of file </home/segonpin/lib/dealii/source/base/subscriptor.cc> in function
    virtual dealii::Subscriptor::~Subscriptor()
The violated condition was: 
    counter == 0
The name and call sequence of the exception was:
    ExcInUse (counter, object_info->name(), infostring)
Additional Information: 
Object of class N6dealii13TriangulationILi1ELi1EEE is still used by 1 other objects.

(Additional information: <none>)

See the entry in the Frequently Asked Questions of deal.II (linked to from http://www.dealii.org/) for a lot more information on what this error means and how to fix programs in which it happens.

Stacktrace:
-----------
#0  /home/segonpin/lib/dealii-8.4.bin/lib/libdeal_II.g.so.8.4.2: dealii::Subscriptor::~Subscriptor()
#1  /home/segonpin/lib/dealii-8.4.bin/lib/libdeal_II.g.so.8.4.2: dealii::Triangulation<1, 1>::~Triangulation()
#2  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: Forest::ProbGeom<1>::~ProbGeom()
#3  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: 
#4  python: PyObject_Call
#5  python: PyObject_CallFunctionObjArgs
#6  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: 
#7  python: ) [0x4fd4e6]
#8  python: PyDict_SetItem
#9  python: _PyModule_Clear
#10  python: PyImport_Cleanup
#11  python: Py_Finalize
#12  python: Py_Main
#13  /lib/x86_64-linux-gnu/libc.so.6: __libc_start_main
#14  python: _start
--------------------------------------------------------

当我以正确的顺序手动删除产生问题的两个类时，错误消失了

#!/usr/bin/python
import pyinput
import pygeom
import pystate
import pyeqfactory
import pyeigenprobfactory
import pyeigensolver

inp = pyinput.Input("heter1d/1d1g_heter")
geo = pygeom.ProbGeom1D(inp)
state = pystate.State1D(inp, geo);
equation = pyeqfactory.EqFactory1D.New(state)
eigenprob = pyeigenprobfactory.EigenProbFactory1D.New(state, equation)
solver = pyeigensolver.EigenSolver1D(state, eigenprob)
solver.solve_eigenproblem()
print state.get_keff()

# these two lines solve the problem
del state
del geo

不应该是python以相同的顺序删除这些实例（因为state的构造函数中使用了geo）？谢谢！

---

编辑 2017 年 2 月 15 日，11:19。

我可以添加一些额外的原因来说明为什么我需要按特定顺序删除。我正在使用 swig 来解析一个 c++ 库（www.dealii.org），当我创建一个需要 A 实例才有意义的 B 实例时，A 中的一个计数器会增加，表示它由 B 拥有。这用于删除对象（B需要A存在，所以我们在删除A之前删除B）。如果您以其他方式执行此操作，则会出现错误。在这种情况下，python 实例包含其中一些依赖项，因此我必须删除特定其他对象中的对象以避免错误消息。

我在 python 析构函数中添加了一些消息

#!/usr/bin/python
import pyinput
import pygeom
import pystate
import pyeqfactory
import pyeigenprobfactory
import pyeigensolver

def deltalk(self):
  print type(self).__name__ ," die"

pyinput.Input.__del__ = deltalk
pygeom.ProbGeom1D.__del__ = deltalk
pystate.State1D.__del__ = deltalk
pyeqfactory.EqFactory1D.__del__ = deltalk
pyeigenprobfactory.EigenProbFactory1D.__del__ = deltalk
pyeigensolver.EigenSolver1D.__del__ = deltalk
pypostprocessing.PostProcessing1D.__del__ = deltalk

inp = pyinput.Input("heter1d/1d1g_heter")
geo = pygeom.ProbGeom1D(inp)
state = pystate.State1D(inp, geo);
equation = pyeqfactory.EqFactory1D.New(state)
eigenprob = pyeigenprobfactory.EigenProbFactory1D.New(state, equation)
solver = pyeigensolver.EigenSolver1D(state, eigenprob)

当我运行它时，我发现它并没有按照我需要的方式进行破坏（在 state 之前破坏 geo 在 C++ 中引发错误）

$ python test2_forest.py 
EigenSolver1D  die
ProbGeom1D  die

--------------------------------------------------------
An error occurred in line <114> of file </home/segonpin/lib/dealii/source/base/subscriptor.cc> in function
    virtual dealii::Subscriptor::~Subscriptor()
The violated condition was: 
    counter == 0
The name and call sequence of the exception was:
    ExcInUse (counter, object_info->name(), infostring)
Additional Information: 
Object of class N6dealii13TriangulationILi1ELi1EEE is still used by 1 other objects.

(Additional information: <none>)

See the entry in the Frequently Asked Questions of deal.II (linked to from http://www.dealii.org/) for a lot more information on what this error means and how to fix programs in which it happens.

Stacktrace:
-----------
#0  /home/segonpin/lib/dealii-8.4.bin/lib/libdeal_II.g.so.8.4.2: dealii::Subscriptor::~Subscriptor()
#1  /home/segonpin/lib/dealii-8.4.bin/lib/libdeal_II.g.so.8.4.2: dealii::Triangulation<1, 1>::~Triangulation()
#2  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: Forest::ProbGeom<1>::~ProbGeom()
#3  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: 
#4  python: PyObject_Call
#5  python: PyObject_CallFunctionObjArgs
#6  /home/segonpin/codessebas/dealii-neutron-transport/python/_pygeom.so: 
#7  python: ) [0x4fd4e6]
#8  python: PyDict_SetItem
#9  python: _PyModule_Clear
#10  python: PyImport_Cleanup
#11  python: Py_Finalize
#12  python: Py_Main
#13  /lib/x86_64-linux-gnu/libc.so.6: __libc_start_main
#14  python: _start

考虑到这种依赖性，有没有一种通用的方法告诉 python 删除对象？还是应该在每个类的析构函数中明确说出来？

谢谢

【问题讨论】：

在构造函数中使用并不意味着什么...你保留对另一个对象的引用吗？

嗨@Tali我正在使用swig来解析一个c ++库（www.dealii.org），当我创建一个需要A实例才有意义的B实例时，计数器是在A中增加了它属于B的说法。这是用于删除对象（B需要A存在，所以我们在删除A之前删除B）。如果您以其他方式执行此操作，则会出现错误。在这种情况下，python 实例包含其中一些依赖项，因此我必须删除特定其他对象中的对象以避免错误消息。

【参考方案1】：

如果将来有人发现同样的问题，我已经找到了一种方法，可以使用atexit 按我想要的顺序调用删除。

不干净但实用的解决方案

不是很干净，但我会是这样的：

#!/usr/bin/python
import pyinput
import pygeom
import pystate
import pyeqfactory
import pyeigenprobfactory
import pyeigensolver

def goodbye() :
  print "Goodbye!!\n"
import atexit
atexit.register(goodbye)

def deltalk(self):
  print self.__class__.__name__ ," die"

pyinput.Input.__del__ = deltalk
pygeom.ProbGeom1D.__del__ = deltalk
pystate.State1D.__del__ = deltalk
pyeqfactory.Equation1D.__del__ = deltalk
pyeigenprobfactory.EigenProb1D.__del__ = deltalk
pyeigensolver.EigenSolver1D.__del__ = deltalk
pypostprocessing.PostProcessing1D.__del__ = deltalk

inp = pyinput.Input("heter1d/1d1g_heter")
atexit.register(inp.__del__)

geo = pygeom.ProbGeom1D(inp)
atexit.register(geo.__del__)

state = pystate.State1D(inp, geo);
atexit.register(state.__del__)

equation = pyeqfactory.EqFactory1D.New(state)
atexit.register(equation.__del__)

eigenprob = pyeigenprobfactory.EigenProbFactory1D.New(state, equation)
atexit.register(eigenprob.__del__)

solver = pyeigensolver.EigenSolver1D(state, eigenprob)
atexit.register(solver.__del__)

当我运行脚本时，我得到了

$ python test2_forest.py
EigenSolver1D  die
EigenProb1D  die
Equation1D  die
State1D  die
State1D  die
ProbGeom1D  die
Input  die
Goodbye!!

Input  die
EigenProb1D  die
State1D  die
ProbGeom1D  die
EigenSolver1D  die
Equation1D  die

如果可以直接修改构造函数就更好了

如果我可以在构造函数中添加atexit.register 会容易得多，如下例所示

#!/usr/bin/python
import atexit

class Foo(object):
  def __init__(self, id):
    self.id = id
    atexit.register(self.__del__)
  def __del__(self):
    print(self.id, " says bye")

a = Foo(1)
b = Foo(2)
c = Foo(3)

但是类是用c++定义的，用SWIG解析的，所以我需要修改一个现有类定义的构造函数来做这样的事情，所以对于一个小程序来说手动做起来更容易。

修改现有构造函数...

如果您必须为许多课程这样做，但如果您仍想避免手动注册，这不是最佳选择。类 foo 如下

#simplefoo.py
class Foo(object):
  def __init__(self, id):
    self.id = id

现有类的构造函数可以修改如下

#test.py
from simplefoo import Foo

# first: I load the module atexit and register the bye function    
import atexit
def bye():
  print("Bye bye!")
atexit.register(bye)

# second: I add the destructor that talks loudly
def del_ini(self):
  print(self.id, " says bye")
Foo.__del__ = del_ini 

# third: I modify the original constructor. This is ugly
Foo.ini_old = Foo.__init__
def ini_new(self, id):
  self.ini_old(id)
  atexit.register(self.__del__)
Foo.__init__ = ini_new

# fourth: I create objects and finish the program them to see what happens

a = Foo(1)
b = Foo(2)
c = Foo(3)

当我们运行脚本时，我们得到

$ python3 test.py 
3  says bye
2  says bye
1  says bye
Bye bye!
3  says bye
1  says bye
2  says bye

谢谢。