The following modules on the Python package index make standard library functionality from later versions of Python available in earlier versions (not all of them are technically backports - some existed on PyPI before being adopted wholesale into the standard library).

 * [[https://pypi.python.org/pypi/selectors34|selectors34]] (Python 3.4+ selectors for 2.6, 2.7 and 3.3)
 * faulthandler (Python 3.3+ faulhandler for 2.x and earlier versions of 3.x)
 * configparser (Python 3.2+ configparser for 2.x)
 * subprocess32 (provides equivalent functionality to the standard library's subprocess module as of Python 3.2)
 * unittest2 (provides equivalent functionality to the standard library's unittest module as of Python 2.7/3.2)
 * contextlib2 (provides ExitStack, in the standard library's contextlib module as of Python 3.3)
 * funcsigs (in the standard library's inspect module as of Python 3.3)
 * futures (in the standard library as concurrent.futures as of Python 3.2)
 * mock (in the standard library as unittest.mock as of Python 3.3)
 * cdecimal (default implementation for the standard library's decimal module as of Python 3.3)
 * enum34 (in the standard library as enum as of Python 3.3)
 * singledispatch (in the standard library's functools module as of Python 3.4)
 * logutils (logging functionality added in 2.7 and 3.2+, such as `dictConfig` / `QueueHandler` / `QueueListener`)
 * argparse (included in the standard library since Python 2.7/3.2) 

The following modules on PyPI inspired later standard library additions, but have different APIs:

 * flufl.enum (initial inspiration for what became the standard library's )
 * ipaddr (initial inspiration for the standard library's ipaddress module as of Python 3.3)