Private Constructor in Python

Question

How do I create a private constructor which should be called only by the static function of the class and not from else where?

Answer 1

class MongoConn(object):
    @classmethod
    def instance(cls):
        if not hasattr(cls, '_instance'):
            cls._instance = cls()
        return cls._instance

    def __init__(self):
        assert not hasattr(self.__class__, '_instance'), 'Do not call constructor directly!'

If you want a single instance.