Does python have any sort of built in functionality of notifying what dictionary elements changed upon dict update? For example I am looking for some functionality like this:

>>> a = {'a':'hamburger', 'b':'fries', 'c':'coke'}
>>> b = {'b':'fries', 'c':'pepsi', 'd':'ice cream'}
>>> a.diff(b)
{'c':'pepsi', 'd':'ice cream'}
>>> a.update(b)
>>> a
{'a':'hamburger', 'b':'fries', 'c':'pepsi', 'd':'ice cream'}

I am looking to get a dictionary of the changed values as shown in the result of a.diff(b)