Hello Peter,
Peter Otten <__pete...@web.de> writes:
> Is there an actual use case?
I discussed this in the german newsgroup. Here is the use in my class:
-----------------------------8<-----------------------
import threading
import weakref
class DoAsync(threading.Thread):
def __init__(self, func):
threading.Thread.__init__(self)
self.setDaemon(True)
self._cond = threading.Condition()
self.scheduled = False
self._func = weakref.ref(func, self._cleanup)
self.start()
def run(self):
while self._func():
with self._cond:
while not self.scheduled and self._func():
self._cond.wait()
self.scheduled = False
func = self._func()
if func:
func()
def __call__(self):
with self._cond:
self.scheduled = True
self._cond.notify()
def _cleanup(self, ref):
self()
-----------------------------8<-----------------------
The use for this callable class is to take a function call, and whenever
the DoAsync object is called, trigger a call to the stored function.
Other classes use it like:
-----------------------------8<-----------------------
class MyClass:
def __init__(self):
...
self.update = DoAsync(self._do_update)
def _do_update(self):
do_something_that_takes_long_and_shall_be_done_after_an_update()
-----------------------------8<-----------------------
Since DoAsync starts its own thread, I get a classical deadlock
situation: DoAsync needs a reference to the method to be called, and as
long as the thread is running, the MyClass object (which contains the
method) cannot be cleaned up. This would be a classic case for a weak
reference, if Python would not create it at calling time.
> No. o.myfunc is a different object, a bound method, and every time you
> access o's myfunc attribute a new bound method is created:
What is the reason for that behaviour? It looks quite silly to me.
And how can I get a reference to a bound method that lives as long as
the method itself?
Regards
Ole
--
http://mail.python.org/mailman/listinfo/python-list
