Changed 3.3.4:
PEP 380, syntax for delegating to a subgenerator (yield from)
PEP 393, flexible string representation (doing away with the distinction between "wide" and "narrow" Unicode builds)
A C implementation of the "decimal" module, with up to 120x speedup for decimal-heavy applications
The import system (__import__) is based on importlib by default
The new "lzma" module with LZMA/XZ support
PEP 397, a Python launcher for Windows
PEP 405, virtual environment support in core
PEP 420, namespace package support
PEP 3151, reworking the OS and IO exception hierarchy
PEP 3155, qualified name for classes and functions
PEP 409, suppressing exception context
PEP 414, explicit Unicode literals to help with porting
PEP 418, extended platform-independent clocks in the "time" module
PEP 412, a new key-sharing dictionary implementation that significantly saves memory for object-oriented code
PEP 362, the function-signature object
The new "faulthandler" module that helps diagnosing crashes
The new "unittest.mock" module
The new "ipaddress" module
The "sys.implementation" attribute
A policy framework for the email package, with a provisional (see PEP 411) policy that adds much improved unicode support for email header parsing
A "collections.ChainMap" class for linking mappings to a single unit
Wrappers for many more POSIX functions in the "os" and "signal" modules, as well as other useful functions such as "sendfile()"
Hash randomization, introduced in earlier bugfix releases, is now switched on by default


(adam)