Python, using singleton pattern or just global variable

问题

In python, is it better that using the singleton pattern instead of using global variable?

class Singleton(type):
    def __call__(self, *args, **kwargs):
        if 'instance' not in self.__dict__:
            self.instance = super(Singleton, self).__call__(*args, **kwargs)
        return self.instance

or just make a global variable:

SINGLETON_VARIABLE = None
def getSingleton():
    if SINGLETON is None:
        SINGLETON_VARIABLE = SOME_ININ_CLASS()
    return SINGLETON_VARIABLE

Is it necessary to complicate the life to make a singleton pattern? Thank you in advance.

回答1:

The problem with the global variable approach would be that you can always access that variable and modify its content, so it would be a "weaker" form of the Singleton pattern. Also, if you have more than one Singleton class, you have to define a function and a global variable for each, so it ends up being messier than the pattern.

来源：https://stackoverflow.com/questions/25429349/python-using-singleton-pattern-or-just-global-variable