persistent

from persistent import Persistent class MyPersistentObject(Persistent): def __init__(self, name="Default"): self.name = name self.attributes = {} # A mutable dictionary def update_name(self, new_name): # Assigning to a direct attribute will mark the object dirty self.name = new_name def add_attribute(self, key, value): # For objects managed by a persistence layer (e.g., ZODB), # modifying this dict would also mark the parent dirty. # Without a persistence layer, direct dict modification here # does NOT automatically set _p_changed. self.attributes[key] = value def describe(self): return f"Name: {self.name}, Attributes: {self.attributes}" # Create an instance my_obj = MyPersistentObject("Initial Name") print(f"1. Initial state: {my_obj.describe()}, _p_changed: {my_obj._p_changed}") # Modifying a direct attribute marks it dirty my_obj.update_name("New Name 1") print(f"2. After update_name: {my_obj.describe()}, _p_changed: {my_obj._p_changed}") # Simulate 'saving' (a persistence layer would set _p_changed to None) my_obj._p_changed = None print(f"3. After 'saving': {my_obj.describe()}, _p_changed: {my_obj._p_changed}") # Modifying the mutable dictionary directly (without a storage proxy) # does NOT automatically set _p_changed, which is a common gotcha. my_obj.attributes['version'] = 1 print(f"4. After modifying internal dict: {my_obj.describe()}, _p_changed: {my_obj._p_changed}") # To ensure persistence layer detects changes in mutable objects, # you often need to manually set _p_changed or reassign the attribute # (e.g., obj.attributes = new_dict_or_copy) or rely on a proxy provided by the storage. my_obj._p_changed = True print(f"5. Manually set _p_changed after internal change: {my_obj.describe()}, _p_changed: {my_obj._p_changed}")