如何在Flask微框架中创建单例对象

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///example.db'
db = SQLAlchemy(app)

class Singleton(object):
    _instance = None

    def __new__(cls, *args, **kwargs):
        if not cls._instance:
            cls._instance = super(Singleton, cls).__new__(cls, *args, **kwargs)
        return cls._instance

class MySingleton(Singleton):
    def __init__(self):
        # 初始化代码
        pass

@app.route('/')
def index():
    singleton = MySingleton()
    # 使用单例对象
    return 'Hello World'

if __name__ == '__main__':
    app.run()