A piece of code that you can't read (about descriptors)

1 classCallbackproperty (object):2     """A property that would alert observers when upon updates"""3 4     def __init__(Self, default=None):5Self.data =dict ()6Self.default =default7Self.callbacks =dict ()8 9     def __get__(self, instance, owner):Ten         ifInstance isNone: One             return Self A         returnSelf.data.get (instance, Self.default) -  -     def __set__(self, instance, value): the          forCallbackinchSelf.callbacks.get (instance, []): -             #Alert callback function of new value - callback (value) -Self.data[instance] =value +  -     defAdd_callback (self, instance, callback): +         """Add A new function to call everytime the descriptor within instance updates""" A         ifInstance not inchself.callbacks: atSelf.callbacks[instance] = [] - Self.callbacks[instance].append (callback) -  - classBankAccount (object): -Balance =callbackproperty (0) -  in deflow_balance_warning (value): -     ifValue < 100: to         Print("You is now poor") +  -BA =BankAccount () the BankAccount.balance.add_callback (BA, low_balance_warning) *  $Ba.balance = 5000Panax Notoginseng Print("Balance is%s"%ba.balance) -Ba.balance = 99

A piece of code that you can't read (about descriptors)