I don't know if this is the correct place to send this question.
I've checked out some ways to get this to work. I want to be able to
add a new function to an instance of an object. I've tested two
different methods that cause problems with 'deleting'/garbage collection
(__del__ may never get called), but implemented one sort of hackishly
maybe that works find. I'm wondering if there is more of an official way
than mine.
1.
import new
import gc
class A:
def __del__(x):
print "Deleting"
def f(x):
print x
a = A()
a.f = new.instancemethod(a,f)
a.f() # This works
del a # Not what is expected
gc.collect() # Works, but __del__ does not get called
2.
import gc
def addmethod(self,func,name):
def wrapper(*args,**kwargs):
return func(self,*args,**kwargs)
setattr(self,name,func)
class A:
def __del__(x):
print "Deleting"
def f(x):
print x
a = A()
addmethod(a, f, "f")
a.f() # Works as expected
del a # nope
gc.collect() # Still __del__ doesn't get called
3. Slightly hackish method, maybe some problems
import gc
import weakref
def addmethod(self,func,name):
# change the value of 'self' so wrapper.func_globals will reference
the new value
self = weakref.ref(self)
def wrapper(*args,**kwargs):
return func(self(),*args,**kwargs)
setattr(self(),name,func)
class A:
def __del__(x):
print "Deleting"
def f(x):
print x
a = A()
addmethod(a, f, "f")
a.f() # Works as expected
del a
gc.collect()
With this method 'del a' does the expected most of the time, and
"Deleting" does get printed or when calling 'gc.collect()' it prints
correctly. This seems the best approach so that when 'a' is no longer
valid, the object can die instead of continuing to exitng because
wrapper.func_globals still contains a reference, but seems very hackish
an maybe problematic. I'm wondering if there is a better way?
Brian Vanderburg II
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