Choosing The SSL Version In Python Requests

Over the last few months (and probably for quite a while before then too), a
few issues have been raised on the
Requests GitHub page asking how to
select the version of SSL used by Requests. This is actually simple once you
know how, so I thought I’d write a short post to show you how it’s done.

A quick note before we begin: it is not possible to select the version of SSL
you want to use before Requests v1.0.0 without changing the underlying
library code. The following set of instructions will not work if you’re running
an earlier version.

How It’s Done

Altogether this is relatively simple. To change the SSL version used in HTTPS,
you are expected to subclass the HTTPAdapter class and mount it to a
Session object. If, for example, you wanted to force the use of TLSv1, your
new Transport Adapter will look like this:

from requests.adapters import HTTPAdapter
from requests.packages.urllib3.poolmanager import PoolManager
import ssl

class MyAdapter(HTTPAdapter):
    def init_poolmanager(self, connections, maxsize, block=False):
        self.poolmanager = PoolManager(num_pools=connections,
                                       maxsize=maxsize,
                                       block=block,
                                       ssl_version=ssl.PROTOCOL_TLSv1)

With that done, you can mount it to a Requests Session object:

import requests
s = requests.Session()
s.mount('https://', MyAdapter())

Of course, this is so easy that it’s simple to write a Transport Adapter that
can take an arbitrary SSL type from the ssl package in the constructor and
use that. Whack this in a file and import it into whatever you’re doing:

from requests.adapters import HTTPAdapter
from requests.packages.urllib3.poolmanager import PoolManager

class SSLAdapter(HTTPAdapter):
    '''An HTTPS Transport Adapter that uses an arbitrary SSL version.'''
    def __init__(self, ssl_version=None, **kwargs):
        self.ssl_version = ssl_version

        super(SSLAdapter, self).__init__(**kwargs)

    def init_poolmanager(self, connections, maxsize, block=False):
        self.poolmanager = PoolManager(num_pools=connections,
                                       maxsize=maxsize,
                                       block=block,
                                       ssl_version=self.ssl_version)

You can mount it to a Session object and just go to town.

Hopefully this will be of use to people. If you have any problems or
improvements, leave a note in the comments or drop me a line on Twitter (the
url is in the sidebar).

EDIT: Fixed broken code in constructor.

EDIT (22/06/13): Brought code up to date with Requests v1.2.3.

EDIT (28/08/13): Actually brought code up to date with Requests v1.2.3.