Python實現單例模式的5種方法
基本介紹
一個對象隻允許被一次創建,一個類隻能創建一個對象,並且提供一個全局訪問點。
單例模式應該是應用最廣泛,實現最簡單的一種創建型模式。
特點:全局唯一,允許更改
優缺點
優點:
- 避免對資源的多重占用,如寫入文件操作
- 節省內存
- 防止命名空間被污染
缺點:
- 沒有接口,不能繼承,與單一職責原則沖突,一個類應該隻關心內部邏輯,而不關心外面怎麼樣來實例化
Python實現
方式1,元類實現:
class MetaClass(type): def __call__(self, *args, **kwargs): """ self : class Singleton """ if not hasattr(self, "ins"): insObject = super(__class__, self).__call__(*args, **kwargs) setattr(self, "ins", insObject) return getattr(self, "ins") class Singleton(object, metaclass=MetaClass): pass if __name__ == "__main__": ins = Singleton() print(id(ins)) ins = Singleton() print(id(ins))
方式2,繼承實現:
class ParentClass: def __new__(cls, *args, **kwargs) -> object: """ cls : class Singeton """ if not hasattr(cls, "ins"): insObject = super(__class__, cls).__new__(cls, *args, **kwargs) setattr(cls, "ins", insObject) return getattr(cls, "ins") class Singleton(ParentClass): pass if __name__ == "__main__": ins = Singleton() print(id(ins)) ins = Singleton() print(id(ins))
方式3,裝飾器實現:
def warpper(clsObject): def inner(*args, **kwargs): if not hasattr(clsObject, "ins"): insObject = clsObject(*args, **kwargs) setattr(clsObject, "ins", insObject) return getattr(clsObject, "ins") return inner @warpper class Singleton: pass if __name__ == "__main__": ins = Singleton() print(id(ins)) ins = Singleton() print(id(ins))
方式4,模塊實現:
- foo.py --> ins = Singleton() - bar.py --> from foo import ins
方式5,@classmethod實現單例模式:
class Singleton: @classmethod def getSingletonInstanceObject(cls, *args, **kwargs): if not hasattr(cls, "ins"): insObject = cls(*args, **kwargs) setattr(cls, "ins", insObject) return getattr(cls, "ins") if __name__ == "__main__": ins = Singleton.getSingletonInstanceObject() print(id(ins)) ins = Singleton.getSingletonInstanceObject() print(id(ins))
到此這篇關於Python實現單例模式的5種方法的文章就介紹到這瞭,更多相關Python 單例模式內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet!