__init__和__new__的对比及单例模式

class Book(object):

    #对象生成方法
    def __new__(cls, title):
        # 设计成单例模式
        if not hasattr(cls,"_instance"):
             cls._instance= super().__new__(cls)
        print('in __new__')
        return  cls._instance  

    #对象初始化方法
    def __init__(self, title):
        print('in __init__')
        super().__init__()
        self.title = title

if __name__ == '__main__':
    b = Book('The Spider Book')
    b2= Book('The Flask Book')
    print(id(b))
    print(id(b2))
    print(b.title)
    print(b2.title)