这个模式，我还是了解的。
书上用了三种不同的方法。
class Singleton1:
# 单例实现方式1
__instance = None
__is_first_init = False
def __new__(cls, name):
if not cls.__instance:
Singleton1.__instance = super().__new__(cls)
return cls.__instance
def __init__(self, name):
if not self.__is_first_init:
self.__name = name
self.__is_first_init = True
def get_name(self):
return self.__name
tony = Singleton1('Tony')
karry = Singleton1('karry')
print(tony.get_name(), karry.get_name())
print(id(tony), id(karry))
print(tony == karry)
print("=======单例实现方式1========")
class Singleton2(type):
# 单例实现方式2
def __init__(cls, what, bases=None, dict=None):
super().__init__(what, bases, dict)
cls._instance = None
def __call__(cls, *args, **kwargs):
if cls._instance is None:
cls._instance = super().__call__(*args, **kwargs)
return cls._instance
class CustomClass(metaclass=Singleton2):
def __init__(self, name):
self.__name = name
def get_name(self):
return self.__name
tony = CustomClass('Tony')
karry = CustomClass('karry')
print(tony.get_name(), karry.get_name())
print(id(tony), id(karry))
print(tony == karry)
print("=======单例实现方式2========")
def singleton_decorator(cls, *args, **kwargs):
instance = {}
def wrapper_singleton(*args, **kwargs):
if cls not in instance:
instance[cls] = cls(*args, **kwargs)
return instance[cls]
return wrapper_singleton
@singleton_decorator
class Singleton3:
# 单例实现方式2
def __init__(self, name):
self.__name = name
def get_name(self):
return self.__name
tony = Singleton3('Tony')
karry = Singleton3('karry')
print(tony.get_name(), karry.get_name())
print(id(tony), id(karry))
print(tony == karry)
print("=======单例实现方式3========")
C:\Python36\python.exe C:/Users/Sahara/PycharmProjects/test1/test.py Tony Tony 39257648 39257648 True =======单例实现方式1======== Tony Tony 39257984 39257984 True =======单例实现方式2======== Tony Tony 39257928 39257928 True =======单例实现方式3======== Process finished with exit code 0