潇潇雨雨
这是我自己的单身汉的实现。您所要做的就是装饰类；要获得单例，则必须使用Instance方法。下面是一个例子：@Singletonclass Foo:
def __init__(self):
print 'Foo created'f = Foo() # Error, this isn't how you get the instance of a singletonf = Foo.instance()
# Good. Being explicit is in line with the Python Zeng = Foo.instance() # Returns already created instanceprint f is g # True这是密码：class Singleton:
"""
A non-thread-safe helper class to ease implementing singletons.
This should be used as a decorator -- not a metaclass -- to the
class that should be a singleton.
The decorated class can define one `__init__` function that
takes only the `self` argument. Also, the decorated class cannot be
inherited from. Other than that, there are no restrictions that apply
to the decorated class.
To get the singleton instance, use the `instance` method. Trying
to use `__call__` will result in a `TypeError` being raised.
"""
def __init__(self, decorated):
self._decorated = decorated def instance(self):
"""
Returns the singleton instance. Upon its first call, it creates a
new instance of the decorated class and calls its `__init__` method.
On all subsequent calls, the already created instance is returned.
"""
try:
return self._instance except AttributeError:
self._instance = self._decorated()
return self._instance def __call__(self):
raise TypeError('Singletons must be accessed through `instance()`.')
def __instancecheck__(self, inst):
return isinstance(inst, self._decorated)