【Tornado笔记】tornado.web.IOLoop和tornado.util.Configurable

2 minute read
python

上一篇文章tornado的 Hello, world 还没有分析完 还差最后一句

import tornado.ioloop
import tornado.web

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello, world")

application = tornado.web.Application([
    (r"/", MainHandler),
])

if __name__ == "__main__":
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()

IOLoop就是整个tornado区别于其他框架的最关键的地方。

一、tornado.ioloop.IOLoop.instance

@staticmethod
def instance():
    if not hasattr(IOLoop, "_instance"):
        with IOLoop._instance_lock:
            if not hasattr(IOLoop, "_instance"):
                # New instance after double check
                IOLoop._instance = IOLoop()
    return IOLoop._instance

每个tornado进程都会有一个全局的IOLoop实例，这个方法就是用来获得这个实例的。

with IOLoop._instance_lock保证了创建的这个实例的过程是线程安全的。

IOLoop继承了tornado.util.Configurable。Configurable （是一个“抽象”类）实现了__new__，所以将自动调用了__new__生成IOLoop的实例。

二、tornado.util.Configurable.__new__()

def __new__(cls, **kwargs):
    base = cls.configurable_base()
    args = {}
    if cls is base:
        impl = cls.configured_class()
        if base.__impl_kwargs:
            args.update(base.__impl_kwargs)
    else:
        impl = cls
    args.update(kwargs)
    instance = super(Configurable, cls).__new__(impl)
    # initialize vs __init__ chosen for compatibility with AsyncHTTPClient
    # singleton magic.  If we get rid of that we can switch to __init__
    # here too.
    instance.initialize(**args)
    return instance</pre></div>
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