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Python 3.7¶

New Features:

Feature		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__`	Partial
PEP 563	Postponed Evaluation of Annotations
PEP 564	Time functions with nanosecond resolution	Partial 1
PEP 565	Show DeprecationWarning in `__main__`
PEP 567	Context Variables

Other Language Changes:

`async` and `await` are now reserved keywords	Complete
`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 when `from ... 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
Too many to list
gc
New features include gc.freeze(), gc.unfreeze(), gc-get_freeze_count
math
math.remainder() added to implement IEEE 754-style remainder
re
A number of tidy up features including better support for splitting on empty strings and copy support for compiled expressions and match objects
sys
sys.breakpointhook() added. sys.get(/set)_coroutine_origin_tracking_depth() added
time
Mostly updates to support nanosecond resolution in PEP564, see above

Notes