Hi,
I've written a decorator that prints exceptions and I'm having some
trouble with garbage collection.
My decorator is:
import sys
def print_exception_decorator(fn):
def decorator(self, *args, **kwds):
try:
return fn(*args, **kwds)
except:
print 'Exception:', sys.exc_info()
raise
return decorator
The class I want to decorate the methods of is:
class InstanceCounted(object):
"A class that keeps track of how many instances there are."
count = 0
def __init__(self):
InstanceCounted.count += 1
def __del__(self):
InstanceCounted.count -= 1
class A(InstanceCounted):
"A class that I want to decorate a method on."
def __init__(self):
super(A, self).__init__()
self.method = print_exception_decorator(self.method)
def __del__(self):
del self.method
def method(self):
pass
When I run the following it does not seem like my object 'a' is garbage
collected:
print 'Have %d instances' % InstanceCounted.count
print 'Creating A'
a = A()
print 'Have %d instances' % InstanceCounted.count
print 'Deleting A'
del a
print 'Have %d instances' % InstanceCounted.count
This is the output:
Have 0 instances
Creating A
Have 1 instances
Deleting A
Have 1 instances
The InstanceCounted.count is 1 at the end. If I omit the call to
"self.method = print_exception_decorator(self.method)" then the instance
count goes down to 0 as desired. I thought that the decorator might be
holding a reference to the instance through the bound method, so I added
the __del__() but it doesn't fix the problem.
Can anyone suggest anything? Is my technique to decorate bound methods
not a good one? How else should I decorate a bound method?
Thanks in advance,
John.
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