Question

I have a function which repeatedly indexes into a dictionary with the same key. Is it possible to take a reference to the item in question?

def my_function(self, event):
    self.__observers[event] ... #this is get is performed multiple times
    observer_ref = self.__observers[event] #can I make this a reference to the value?

Update:
The goal is to not take a copy of what is at self.__observers[event]. I am looking for behaviour akin to C++, e.g.

int x = 1
int& y = x #reference to y, not a copy

Answer 1

When you assign a value to a name (variable) in Python, the variable is just a reference to the value.

So for example say self.__observers[event] starts as an empty list, the following code would work fine:

assert self.__observers[event] == []
observer_ref = self.__observers[event]
observer_ref.append(1)                    # this modifies self.__observers[event]
assert self.__observers[event] == [1]

However, as pointed out by BrenBarn, if you were to then assign observer_ref a new value, it would not modify self.__observers[event] at all.