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Asynchronous Python HTTP Requests for Humans
============================================
.. image:: https://travis-ci.org/ross/requests-futures.png?branch=master
:target: https://travis-ci.org/ross/requests-futures
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:
.. code-block:: python
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:
.. code-block:: python
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.
.. code-block:: python
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:
.. code-block:: python
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.
.. code-block:: python
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
.. _`requests`: https://github.com/kennethreitz/requests
.. _`concurrent.futures`: http://docs.python.org/dev/library/concurrent.futures.html
.. _backport: https://pypi.python.org/pypi/futures
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