Asynchronous Python HTTP Requests for Humans

Small add-on for the python requests http library. Makes use of python 3.2's concurrent.futures or the backport for prior versions of python.

The additional API and changes are minimal and strives to avoid surprises.

The following synchronous code:

from requests import Session

session = Session()
# first requests starts and blocks until finished
response_one = session.get('http://httpbin.org/get')
# second request starts once first is finished
response_two = session.get('http://httpbin.org/get?foo=bar')
# both requests are complete
print('response one status: {0}'.format(response_one.status_code))
print(response_one.content)
print('response two status: {0}'.format(response_two.status_code))
print(response_two.content)

Can be translated to make use of futures, and thus be asynchronous by creating a FuturesSession and catching the returned Future in place of Response. The Response can be retrieved by calling the result method on the Future:

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)

By default a ThreadPoolExecutor is created with 2 workers. If you would like to adjust that value or share a executor across multiple sessions you can provide one to the FuturesSession constructor.

from concurrent.futures import ThreadPoolExecutor
from requests_futures.sessions import FuturesSession

session = FuturesSession(executor=ThreadPoolExecutor(max_workers=10))
# ...

As a shortcut in case of just increasing workers number you can pass max_workers straight to the FuturesSession constructor:

from requests_futures.sessions import FuturesSession
session = FuturesSession(max_workers=10)

That's it. The api of requests.Session is preserved without any modifications beyond returning a Future rather than Response. As with all futures exceptions are shifted (thrown) to the future.result() call so try/except blocks should be moved there.

Working in the Background

There is one additional parameter to the various request functions, background_callback, which allows you to work with the Response objects in the background thread. This can be useful for shifting work out of the foreground, for a simple example take json parsing.

from pprint import pprint
from requests_futures.sessions import FuturesSession

session = FuturesSession()

def bg_cb(sess, resp):
    # parse the json storing the result on the response object
    resp.data = resp.json()

future = session.get('http://httpbin.org/get', background_callback=bg_cb)
# do some other stuff, send some more requests while this one works
response = future.result()
print('response status {0}'.format(response.status_code))
# data will have been attached to the response object in the background
pprint(response.data)

Installation

pip install requests-futures