Cyclic references et C libraries
fabsk+news at free.fr
Wed Aug 13 10:12:19 CEST 2003
I have a problem with a python module that uses C objects. In this
module (not mine, found on the net), I have one parent objet that
maintains a list of child objects. The child objects have a reference on
the parent object, so there is a cycle.
The parent object has a file handle (it is a native C object, not a
python "file object") as a member. This handle can be used with
functions like "lib_open", "lib_close", "lib_read_section".
My problem is that:
- I can not release the parent object in a fully automated manner, so
there is a leak, and since there is a native object, the handle will not
be closed. I can not modify the library to wrap the handle in a class,
because if such a class has a "__del__" method the python garbage
collector will not clean the cycle
I find it not funny to have leaks in Python, and to have to clean objet
One solution would be to wrap the parent objet in a new class
(forwarding all the calls to the parent object). In the "__del__" method
of this class, I would clean the list of children object, and then
remove the reference on the parent objet so its "__del__" method will be
called. Am I right ?
Last question: why does the python file objects not have a "__del__"
method ? How the file can be closed when the last reference is remove ?
If I do a simple test, there is not file leak:
self.file = open("tata")
a = Toto()
b = Toto()
a.member = b
b.member = a
The GC can clean the cycle because the file object doesn't have a
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