python异步特殊类方法__delete__ [英] python async special class methods __delete__

问题描述

海峡要点：

如何异步定义特殊类方法，例如 __ delete __ 在python中？

How can I async def specials class methods like __delete__ in python ?

为什么我需要这样做：

实现一个在多个进程之间共享的良好的缓存系统，我想一次从数据库检索数据并将其存储在缓存中，修改缓存中的数据以及何时不再使用该数据：更新数据库。我的问题是，为了知道哪个实例是最后一个实例，我想异步使用__delete__特殊方法

In order to implement a nice caching system shared between multiple process, I want to retrieve the data from the database once and store them in a cache, modify the data in the cache and when the data is not used anymore: update the database. My problem is, in order to know which instance is the last one, I want to use the __delete__ special method asyncly

def asyncinit(cls):
    """Credits: http://stackoverflow.com/a/33140788/4241798"""
    __new__ = cls.__new__

    async def init(obj, *arg, **kwarg):
        await obj.__init__(*arg, **kwarg)
        return obj

    def new(cls, *arg, **kwarg):
        obj = __new__(cls, *arg, **kwarg)
        coro = init(obj, *arg, **kwarg)
        return coro

    cls.__new__ = new
    return cls

@asyncinit
class AsyncUser:
    async def __init__(self, id: int):
        self.id = id
        with await cachepool as cache:
            cache.hincr(f"users:{id}", "refcnt")

    async def __delete__(self):
        """Won't work"""
        with await cachepool as cache:
            refcnt = await cache.hincrby(f"users:{self.id}", "refcnt", -1)
            if refcnt == 0:
                # update database

    # rest of the class...

推荐答案

不可能同步def python的builint方法，但是可以使用<来调度循环外的协程调用a href = https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.AbstractEventLoop.create_future rel = nofollow noreferrer> loop.create_future 或 asyncio.ensure_future

It is impossible to async def python's builint methods but it is possible to schedule a coroutine call outside the loop using loop.create_future or asyncio.ensure_future

class asyncdel:
    def __delete__(self):
        asyncio.ensure_future(free(self.__dict__.copy()))

async def free(data):
    pass

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