파이썬으로 작성된 프로토타입
프로토타입은 객체들(복잡한 객체 포함)을 그의 특정 클래스들에 결합하지 않고 복제할 수 있도록 하는 생성 디자인 패턴입니다.
모든 프로토타입 클래스들은 객체들의 구상 클래스들을 알 수 없는 경우에도 해당 객체들을 복사할 수 있도록 하는 공통 인터페이스가 있어야 합니다. 프로토타입 객체들은 전체 복사본들을 생성할 수 있습니다. 왜냐하면 같은 클래스의 객체들은 서로의 비공개 필드들에 접근할 수 있기 때문입니다.
복잡도:
인기도:
사용 사례들: 프로토타입 패턴은 copy 모듈을 통해 파이썬에서 바로 사용할 수 있습니다.
식별: 프로토타입은 clone 또는 copy 등의 메서드들의 유무로 식별할 수 있습니다.
개념적인 예시
이 예시는 프로토타입 패턴의 구조를 보여주고 다음 질문에 중점을 둡니다:
- 패턴은 어떤 클래스들로 구성되어 있나요?
- 이 클래스들은 어떤 역할을 하나요?
- 패턴의 요소들은 어떻게 서로 연관되어 있나요?
main.py: 개념적인 예시
import copy
class SelfReferencingEntity:
def __init__(self):
self.parent = None
def set_parent(self, parent):
self.parent = parent
class SomeComponent:
"""
Python provides its own interface of Prototype via `copy.copy` and
`copy.deepcopy` functions. And any class that wants to implement custom
implementations have to override `__copy__` and `__deepcopy__` member
functions.
"""
def __init__(self, some_int, some_list_of_objects, some_circular_ref):
self.some_int = some_int
self.some_list_of_objects = some_list_of_objects
self.some_circular_ref = some_circular_ref
def __copy__(self):
"""
Create a shallow copy. This method will be called whenever someone calls
`copy.copy` with this object and the returned value is returned as the
new shallow copy.
"""
# First, let's create copies of the nested objects.
some_list_of_objects = copy.copy(self.some_list_of_objects)
some_circular_ref = copy.copy(self.some_circular_ref)
# Then, let's clone the object itself, using the prepared clones of the
# nested objects.
new = self.__class__(
self.some_int, some_list_of_objects, some_circular_ref
)
new.__dict__.update(self.__dict__)
return new
def __deepcopy__(self, memo=None):
"""
Create a deep copy. This method will be called whenever someone calls
`copy.deepcopy` with this object and the returned value is returned as
the new deep copy.
What is the use of the argument `memo`? Memo is the dictionary that is
used by the `deepcopy` library to prevent infinite recursive copies in
instances of circular references. Pass it to all the `deepcopy` calls
you make in the `__deepcopy__` implementation to prevent infinite
recursions.
"""
if memo is None:
memo = {}
# First, let's create copies of the nested objects.
some_list_of_objects = copy.deepcopy(self.some_list_of_objects, memo)
some_circular_ref = copy.deepcopy(self.some_circular_ref, memo)
# Then, let's clone the object itself, using the prepared clones of the
# nested objects.
new = self.__class__(
self.some_int, some_list_of_objects, some_circular_ref
)
new.__dict__ = copy.deepcopy(self.__dict__, memo)
return new
if __name__ == "__main__":
list_of_objects = [1, {1, 2, 3}, [1, 2, 3]]
circular_ref = SelfReferencingEntity()
component = SomeComponent(23, list_of_objects, circular_ref)
circular_ref.set_parent(component)
shallow_copied_component = copy.copy(component)
# Let's change the list in shallow_copied_component and see if it changes in
# component.
shallow_copied_component.some_list_of_objects.append("another object")
if component.some_list_of_objects[-1] == "another object":
print(
"Adding elements to `shallow_copied_component`'s "
"some_list_of_objects adds it to `component`'s "
"some_list_of_objects."
)
else:
print(
"Adding elements to `shallow_copied_component`'s "
"some_list_of_objects doesn't add it to `component`'s "
"some_list_of_objects."
)
# Let's change the set in the list of objects.
component.some_list_of_objects[1].add(4)
if 4 in shallow_copied_component.some_list_of_objects[1]:
print(
"Changing objects in the `component`'s some_list_of_objects "
"changes that object in `shallow_copied_component`'s "
"some_list_of_objects."
)
else:
print(
"Changing objects in the `component`'s some_list_of_objects "
"doesn't change that object in `shallow_copied_component`'s "
"some_list_of_objects."
)
deep_copied_component = copy.deepcopy(component)
# Let's change the list in deep_copied_component and see if it changes in
# component.
deep_copied_component.some_list_of_objects.append("one more object")
if component.some_list_of_objects[-1] == "one more object":
print(
"Adding elements to `deep_copied_component`'s "
"some_list_of_objects adds it to `component`'s "
"some_list_of_objects."
)
else:
print(
"Adding elements to `deep_copied_component`'s "
"some_list_of_objects doesn't add it to `component`'s "
"some_list_of_objects."
)
# Let's change the set in the list of objects.
component.some_list_of_objects[1].add(10)
if 10 in deep_copied_component.some_list_of_objects[1]:
print(
"Changing objects in the `component`'s some_list_of_objects "
"changes that object in `deep_copied_component`'s "
"some_list_of_objects."
)
else:
print(
"Changing objects in the `component`'s some_list_of_objects "
"doesn't change that object in `deep_copied_component`'s "
"some_list_of_objects."
)
print(
f"id(deep_copied_component.some_circular_ref.parent): "
f"{id(deep_copied_component.some_circular_ref.parent)}"
)
print(
f"id(deep_copied_component.some_circular_ref.parent.some_circular_ref.parent): "
f"{id(deep_copied_component.some_circular_ref.parent.some_circular_ref.parent)}"
)
print(
"^^ This shows that deepcopied objects contain same reference, they "
"are not cloned repeatedly."
)
Output.txt: 실행 결과
Adding elements to `shallow_copied_component`'s some_list_of_objects adds it to `component`'s some_list_of_objects.
Changing objects in the `component`'s some_list_of_objects changes that object in `shallow_copied_component`'s some_list_of_objects.
Adding elements to `deep_copied_component`'s some_list_of_objects doesn't add it to `component`'s some_list_of_objects.
Changing objects in the `component`'s some_list_of_objects doesn't change that object in `deep_copied_component`'s some_list_of_objects.
id(deep_copied_component.some_circular_ref.parent): 4429472784
id(deep_copied_component.some_circular_ref.parent.some_circular_ref.parent): 4429472784
^^ This shows that deepcopied objects contain same reference, they are not cloned repeatedly.
