Hi all
I have read that one should not have to worry about garbage collection
in modern versions of Python - it 'just works'.
I don't want to rely on that. My app is a long-running server, with
multiple clients logging on, doing stuff, and logging off. They can
create many objects, some of them long-lasting. I want to be sure that
all objects created are gc'd when the session ends.
I do have several circular references. My experience is that if I do not
take some action to break the references when closing the session, the
objects remain alive. Below is a very simple program to illustrate this.
Am I missing something? All comments appreciated.
Frank Millman
==================================================
import gc
class delwatcher:
# This stores enough information to identify the object being watched.
# It does not store a reference to the object itself.
def __init__(self, obj):
self.id = (obj.type, obj.name, id(obj))
print('***', *self.id, 'created ***')
def __del__(self):
print('***', *self.id, 'deleted ***')
class Parent:
def __init__(self, name):
self.type = 'parent'
self.name = name
self.children = []
self._del = delwatcher(self)
class Child:
def __init__(self, parent, name):
self.type = 'child'
self.parent = parent
self.name = name
parent.children.append(self)
self._del = delwatcher(self)
p1 = Parent('P1')
p2 = Parent('P2')
c1_1 = Child(p1, 'C1_1')
c1_2 = Child(p1, 'C1_2')
c2_1 = Child(p2, 'C2_1')
c2_2 = Child(p2, 'C2_2')
input('waiting ...')
# if next 2 lines are included, parent and child can be gc'd
# for ch in p1.children:
# ch.parent = None
# if next line is included, child can be gc'd, but not parent
# p1.children = None
del c1_1
del p1
gc.collect()
input('wait some more ...')
--
https://mail.python.org/mailman/listinfo/python-list
I have read that one should not have to worry about garbage collection
in modern versions of Python - it 'just works'.
I don't want to rely on that. My app is a long-running server, with
multiple clients logging on, doing stuff, and logging off. They can
create many objects, some of them long-lasting. I want to be sure that
all objects created are gc'd when the session ends.
I do have several circular references. My experience is that if I do not
take some action to break the references when closing the session, the
objects remain alive. Below is a very simple program to illustrate this.
Am I missing something? All comments appreciated.
Frank Millman
==================================================
import gc
class delwatcher:
# This stores enough information to identify the object being watched.
# It does not store a reference to the object itself.
def __init__(self, obj):
self.id = (obj.type, obj.name, id(obj))
print('***', *self.id, 'created ***')
def __del__(self):
print('***', *self.id, 'deleted ***')
class Parent:
def __init__(self, name):
self.type = 'parent'
self.name = name
self.children = []
self._del = delwatcher(self)
class Child:
def __init__(self, parent, name):
self.type = 'child'
self.parent = parent
self.name = name
parent.children.append(self)
self._del = delwatcher(self)
p1 = Parent('P1')
p2 = Parent('P2')
c1_1 = Child(p1, 'C1_1')
c1_2 = Child(p1, 'C1_2')
c2_1 = Child(p2, 'C2_1')
c2_2 = Child(p2, 'C2_2')
input('waiting ...')
# if next 2 lines are included, parent and child can be gc'd
# for ch in p1.children:
# ch.parent = None
# if next line is included, child can be gc'd, but not parent
# p1.children = None
del c1_1
del p1
gc.collect()
input('wait some more ...')
--
https://mail.python.org/mailman/listinfo/python-list