Python 3.7

New Features:

Features: Status
PEP 538 Coercing the legacy C locale to a UTF-8 based locale  
PEP 539 A New C-API for Thread-Local Storage in CPython  
PEP 540 UTF-8 mode  
PEP 552 Deterministic pyc  
PEP 553 Built-in breakpoint()  
PEP 557 Data Classes  
PEP 560 Core support for typing module and generic types  
PEP 562 Module __getattr__ and __dir__ Partially done
PEP 563 Postponed Evaluation of Annotations  
PEP 564 Time functions with nanosecond resolution  
PEP 565 Show DeprecationWarning in __main__  
PEP 567 Context Variables  

Other Language Changes:

async and await are now reserved keywords Completed
dict objects must preserve insertion-order  
More than 255 arguments can now be passed to a function; a function can now have more than 255 parameters  
bytes.fromhex() and bytearray.fromhex() now ignore all ASCII whitespace, not only spaces  
str, bytes, and bytearray gained support for the new isascii() method, which can be used to test if a string or bytes contain only the ASCII characters  
ImportError now displays module name and module __file__ path whenfrom ... import ... fails  
Circular imports involving absolute imports with binding a submodule to a name are now supported  
object.__format__(x, '') is now equivalent to str(x) rather than format(str(self), '')  
In order to better support dynamic creation of stack traces, types.TracebackType can now be instantiated from Python code, and the tb_next attribute on tracebacks is now writable  
When using the -m switch, sys.path[0] is now eagerly expanded to the full starting directory path, rather than being left as the empty directory (which allows imports from the current working directory at the time when an import occurs)  
The new -X importtime option or the PYTHONPROFILEIMPORTTIME environment variable can be used to show the timing of each module import  

Changes to built-in modules:

asyncio (many, may need a separate ticket)  
New features include gc.freeze(), gc.unfreeze(), gc-get_freeze_count  
math.remainder() added to implement IEEE 754-style remainder  
A number of tidy up features including better support for splitting on empty strings and copy support for compiled expressions and match objects  
sys.breakpointhook() added. sys.get(/set)_coroutine_origin_tracking_depth() added  
Mostly updates to support nanosecond resolution in PEP564, see above