我尝试了python请求库文档中提供的示例。

使用async.map(rs),我获得了响应代码,但我想获得所请求的每个页面的内容。例如,这是行不通的:

out = async.map(rs)
print out[0].content

当前回答

如果您想使用asyncio,则requests-async为请求提供async/await功能- https://github.com/encode/requests-async

其他回答

我知道这已经关闭了一段时间,但我认为推广另一种基于请求库的异步解决方案可能是有用的。

list_of_requests = ['http://moop.com', 'http://doop.com', ...]

from simple_requests import Requests
for response in Requests().swarm(list_of_requests):
    print response.content

文档在这里:http://pythonhosted.org/simple-requests/

也许请求-期货是另一种选择。

from requests_futures.sessions import FuturesSession

session = FuturesSession()
# first request is started in background
future_one = session.get('http://httpbin.org/get')
# second requests is started immediately
future_two = session.get('http://httpbin.org/get?foo=bar')
# wait for the first request to complete, if it hasn't already
response_one = future_one.result()
print('response one status: {0}'.format(response_one.status_code))
print(response_one.content)
# wait for the second request to complete, if it hasn't already
response_two = future_two.result()
print('response two status: {0}'.format(response_two.status_code))
print(response_two.content)

办公文档中也有建议。如果你不想卷入gevent,这是一个不错的选择。

我也尝试过使用python中的异步方法做一些事情,然而我使用twisted进行异步编程的运气要好得多。它的问题较少,并且有良好的文档记录。这里有一个类似于你在twisted中尝试的东西的链接。

http://pythonquirks.blogspot.com/2011/04/twisted-asynchronous-http-request.html

Note

下面的答案不适用于v0.13.0+请求。在写完这个问题之后,异步功能被移到了请求中。但是,您可以用下面的请求替换请求,它应该可以工作。

我保留这个答案,以反映最初的问题,即使用请求< v0.13.0。


异步完成多个任务。异步映射你必须:

为每个对象(任务)定义一个函数 将该函数作为事件钩子添加到请求中 调用异步。映射到所有请求/操作的列表上

例子:

from requests import async
# If using requests > v0.13.0, use
# from grequests import async

urls = [
    'http://python-requests.org',
    'http://httpbin.org',
    'http://python-guide.org',
    'http://kennethreitz.com'
]

# A simple task to do to each response object
def do_something(response):
    print response.url

# A list to hold our things to do via async
async_list = []

for u in urls:
    # The "hooks = {..." part is where you define what you want to do
    # 
    # Note the lack of parentheses following do_something, this is
    # because the response will be used as the first argument automatically
    action_item = async.get(u, hooks = {'response' : do_something})

    # Add the task to our list of things to do via async
    async_list.append(action_item)

# Do our list of things to do via async
async.map(async_list)

不幸的是,据我所知,请求库不具备执行异步请求的能力。您可以在请求周围包装async/await语法,但这将使底层请求的同步性不会降低。如果您想要真正的异步请求,则必须使用其他提供异步请求的工具。其中一个解决方案是aiohttp (Python 3.5.3+)。根据我在Python 3.7 async/await语法中使用它的经验,它工作得很好。下面我写了执行n个web请求的三个实现

使用Python请求库的纯同步请求(sync_requests_get_all) 同步请求(async_requests_get_all),使用Python 3.7中包装的Python请求库async/await语法和asyncio 一个真正的异步实现(async_aiohttp_get_all), Python aiohttp库封装在Python 3.7 async/await语法和asyncio中

"""
Tested in Python 3.5.10
"""

import time
import asyncio
import requests
import aiohttp

from asgiref import sync

def timed(func):
    """
    records approximate durations of function calls
    """
    def wrapper(*args, **kwargs):
        start = time.time()
        print('{name:<30} started'.format(name=func.__name__))
        result = func(*args, **kwargs)
        duration = "{name:<30} finished in {elapsed:.2f} seconds".format(
            name=func.__name__, elapsed=time.time() - start
        )
        print(duration)
        timed.durations.append(duration)
        return result
    return wrapper

timed.durations = []


@timed
def sync_requests_get_all(urls):
    """
    performs synchronous get requests
    """
    # use session to reduce network overhead
    session = requests.Session()
    return [session.get(url).json() for url in urls]


@timed
def async_requests_get_all(urls):
    """
    asynchronous wrapper around synchronous requests
    """
    session = requests.Session()
    # wrap requests.get into an async function
    def get(url):
        return session.get(url).json()
    async_get = sync.sync_to_async(get)

    async def get_all(urls):
        return await asyncio.gather(*[
            async_get(url) for url in urls
        ])
    # call get_all as a sync function to be used in a sync context
    return sync.async_to_sync(get_all)(urls)

@timed
def async_aiohttp_get_all(urls):
    """
    performs asynchronous get requests
    """
    async def get_all(urls):
        async with aiohttp.ClientSession() as session:
            async def fetch(url):
                async with session.get(url) as response:
                    return await response.json()
            return await asyncio.gather(*[
                fetch(url) for url in urls
            ])
    # call get_all as a sync function to be used in a sync context
    return sync.async_to_sync(get_all)(urls)


if __name__ == '__main__':
    # this endpoint takes ~3 seconds to respond,
    # so a purely synchronous implementation should take
    # little more than 30 seconds and a purely asynchronous
    # implementation should take little more than 3 seconds.
    urls = ['https://postman-echo.com/delay/3']*10

    async_aiohttp_get_all(urls)
    async_requests_get_all(urls)
    sync_requests_get_all(urls)
    print('----------------------')
    [print(duration) for duration in timed.durations]

在我的机器上,这是输出:

async_aiohttp_get_all          started
async_aiohttp_get_all          finished in 3.20 seconds
async_requests_get_all         started
async_requests_get_all         finished in 30.61 seconds
sync_requests_get_all          started
sync_requests_get_all          finished in 30.59 seconds
----------------------
async_aiohttp_get_all          finished in 3.20 seconds
async_requests_get_all         finished in 30.61 seconds
sync_requests_get_all          finished in 30.59 seconds