call async io function in coroutine

call_in_coroutine.py

# -*- coding:utf-8 -*-
from tornado.gen import coroutine
from tornado.concurrent import Future
from tornado.ioloop import IOLoop
from tornado.httpclient import AsyncHTTPClient
from functools import wraps, partial

ioloop = IOLoop.instance()
AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient")
httpclient = AsyncHTTPClient()

class Return(Exception):
    def __init__(self, value):
        super(Return, self).__init__()
        self._value = value

    @property
    def value(self):
        return self._value


def subcoroutine(func):
    final_future = Future()
    def _continue_yield(result, future):
        try:
            tmp_result = result.send(future.result())
            if isinstance(tmp_result, Future):
                ioloop.add_callback(_io_callback, result, tmp_result)
            else:
                raise Exception("only support yield future")
        except StopIteration:
            final_future.set_result(None)
        except Return as rvalue:
            final_future.set_result(rvalue.value)
        except Exception as ex:
            final_future.set_exception(ex)

    def _io_callback(result, attach=None):
        if isinstance(attach, Future):
            ioloop.add_future(attach, partial(_continue_yield, result))

    @wraps(func)
    def inner_call(*args, **kwargs):
        result = func(*args, **kwargs)
        attach = result.send(None)
        ioloop.add_callback(_io_callback, result, attach)
        return final_future
    return inner_call

@subcoroutine
def step1(url):
    print("step1, fetch %s url" % url)
    response = yield httpclient.fetch(url)  
    print("step1, fetch %s url ok , http code is:%d" % (url, response.code))
    raise Return(response)

@subcoroutine
def step2(url):
    print("fetch %s" % url)
    response = yield httpclient.fetch(url)
    print("%s url fetch ok, the http code is:%d" % (url, response.code))
    raise Return(response)

@subcoroutine
def call_other_coroutine(url, url2):
    response = yield httpclient.fetch(url)
    print("%s fetch ok" % url)
    yield step2(url2)
    print("%s fetch ok" % url2)

@coroutine
def start():
    response = yield step1("https://www.baidu.com")
    print("https://www.yahoo.com", response.headers)
    response = yield step2("http://www.baidu.com")
    print("http://www.apple.com", response.headers)
    yield call_other_coroutine("https://news.ycombinator.com/", "http://www.quora.com")

ioloop.run_sync(start)