[Python] Decorate setter property of a class

I have a class Tracker defined as below:

class Tracker():
def __init__(self):
self._value = None

@property
def value(self):
return self._value

@value.setter
def value(self, value):
self._value = value


Then I have another class Aggregator, defined as below. This class takes instances of Tracker defined above.

class Aggregator():
def __init__(self,trackers):
self.trackers = trackers

def updator(func):
def wrapper(*args): # this function will be used to wrap the Tracker.value property/descriptor
return_value = func(*args)
self.update() # Call Aggregator.update() method
return return_value
return wrapper

for t in trackers: # list of tracker objects
t.value = updator(t.value) # Causes errors since the t.value no longer references the method but is used to get/set the value
t.__class__.__dict__['value'].fset = updator(t.__class__.__dict__['value'].fset) # Causes AttributeError: readonly attribute


def update(self):
self.value = sum([t.value for t in self.trackers])


I understand why this is happening. My problem is this: how do I decorate the Tracker.value (property/descriptor) so updating a value in any tracker will trigger the Aggregator.update method of the object that includes that tracker?

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