grequests以哪种方式异步?

问题描述

我使用python请求库已有一段时间了，最​​近需要异步发出请求，这意味着我想发送HTTP请求，让我的主线程继续执行，并进行回调请求返回时调用.

自然地，我被带到grequests库( https://github.com/kennethreitz/grequests )，但是我对此行为感到困惑.例如:

import grequests

def print_res(res):
    from pprint import pprint
    pprint (vars(res))

req = grequests.get('http://www.codehenge.net/blog', hooks=dict(response=print_res))
res = grequests.map([req])

for i in range(10):
    print i

上面的代码将产生以下输出:

<...large HTTP response output...>

0
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9

grequests.map()调用显然会阻塞，直到HTTP响应可用为止.似乎我在这里误解了异步"行为，而grequests库仅用于同时执行多个HTTP请求并将所有响应发送到单个回调.这是正确的吗?

解决方案

.map()旨在并行运行多个URL的检索，并且确实会等待这些任务完成(调用gevent.joinall(jobs)). /p>

使用.send()代替，使用 Pool实例:

req = grequests.get('http://www.codehenge.net/blog', hooks=dict(response=print_res))
job = grequests.send(req, grequests.Pool(1))

for i in range(10):
    print i

在没有池的情况下，.send()调用将仍然阻塞，但仅针对执行的gevent.spawn()调用.

I've been using the python requests library for some time, and recently had a need to make a request asynchronously, meaning I would like to send off the HTTP request, have my main thread continue to execute, and have a callback called when the request returns.

Naturally, I was lead to the grequests library (https://github.com/kennethreitz/grequests), but i'm confused about the behavior. For example:

import grequests

def print_res(res):
    from pprint import pprint
    pprint (vars(res))

req = grequests.get('http://www.codehenge.net/blog', hooks=dict(response=print_res))
res = grequests.map([req])

for i in range(10):
    print i

The above code will produce the following output:

<...large HTTP response output...>

0
1
2
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4
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6
7
8
9

The grequests.map() call obviously blocks until the HTTP response is available. It seems likely I misunderstood the 'asynchronous' behavior here, and the grequests library is just for performing multiple HTTP requests concurrently and sending all responses to a single callback. Is this accurate?

解决方案

.map() is meant to run retrieval of several URLs in parallel, and will indeed wait for these tasks to complete (gevent.joinall(jobs)) is called).

Use .send() instead to spawn jobs, using a Pool instance:

req = grequests.get('http://www.codehenge.net/blog', hooks=dict(response=print_res))
job = grequests.send(req, grequests.Pool(1))

for i in range(10):
    print i

Without the pool the .send() call will block still, but only for the gevent.spawn() call it executes.

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