| Section | Video Links |
|---|---|
| Memento Overview |    |
| Memento Use Case | |
| Getters/Setters | |
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python ./memento/memento_concept.py
Originator: Setting state to `State #1`
Originator: Setting state to `State #2`
CareTaker: Getting a copy of Originators current state
Originator: Providing Memento of state to caretaker.
Originator: Setting state to `State #3`
CareTaker: Getting a copy of Originators current state
Originator: Providing Memento of state to caretaker.
Originator: Setting state to `State #4`
State #4
CareTaker: Restoring Originators state from Memento
Originator: State after restoring from Memento: `State #2`
State #2
CareTaker: Restoring Originators state from Memento
Originator: State after restoring from Memento: `State #3`
State #3... Refer to Book, pause Video Lectures or subscribe to Medium Membership to read textual content.
python ./memento/client.py
Score: 200, Level: 0, Location: {'x': 0, 'y': 0, 'z': 2}
Inventory: {'rifle', 'sword'}
CareTaker: Game Save
Score: 500, Level: 1, Location: {'x': 0, 'y': 0, 'z': 13}
Inventory: {'motorbike', 'rifle', 'sword'}
CareTaker: Game Save
Score: 600, Level: 2, Location: {'x': 0, 'y': 0, 'z': 14}
Inventory: {'motorbike', 'rifle', 'sword'}
CareTaker: Restoring Characters attributes from Memento
Score: 200, Level: 0, Location: {'x': 0, 'y': 0, 'z': 2}
Inventory: {'rifle', 'sword'}Often when coding attributes in classes, you may want to provide methods to allow external functions to read or modify a classes internal attributes.
A common approach would be to add two methods prefixed with get_ and set_,
class ExampleClass:
def __init__(self):
self._value = 123
def get_value(self):
return self._value
def set_value(self, value):
self._value = value
example = ExampleClass()
print(example.get_value())This makes perfect sense what the intentions are, but there is a more pythonic way of doing this and that is by using the inbuilt Python @property decorator.
class ExampleClass:
def __init__(self):
self._value = 123
@property
def value(self):
return self._value
@value.setter
def value(self, value):
self._value = value
example = ExampleClass()
print(example.value)Note that in the above example, there is an extra decorator named @value.setter . This is used for setting the _value attribute.
Along with the above two new getter/setter methods, there is also another method for deleting an attribute called deleter .
class ExampleClass:
def __init__(self):
self._value = 123
@property
def value(self):
return self._value
@value.setter
def value(self, value):
self._value = value
@value.deleter
def value(self):
print('Deleting _value')
del self._value
example = ExampleClass()
print(example.value)
del example.value
print(example.value) # now raises an AttributeError... Refer to Book, pause Video Lectures or subscribe to Medium Membership to read textual content.