Summary – Release highlights
New syntax features:
PEP 498, formatted string literals.
PEP 515, underscores in numeric literals.
PEP 526, syntax for variable annotations.
PEP 525, asynchronous generators.
PEP 530: asynchronous comprehensions.
New library modules:
secrets: PEP 506 – Adding A Secrets Module To The Standard Library.
CPython implementation improvements:
The dict type has been reimplemented to use a more compact representation based on a proposal by Raymond Hettinger and similar to the PyPy dict implementation. This resulted in dictionaries using 20% to 25% less memory when compared to Python 3.5.
Customization of class creation has been simplified with the new protocol.
The class attribute definition order is now preserved.
The order of elements in **kwargs now corresponds to the order in which keyword arguments were passed to the function.
DTrace and SystemTap probing support has been added.
The new PYTHONMALLOC environment variable can now be used to debug the interpreter memory allocation and access errors.
Significant improvements in the standard library:
The asyncio module has received new features, significant usability and performance improvements, and a fair amount of bug fixes. Starting with Python 3.6 the asyncio module is no longer provisional and its API is considered stable.
A new file system path protocol has been implemented to support path-like objects. All standard library functions operating on paths have been updated to work with the new protocol.
The datetime module has gained support for Local Time Disambiguation.
The typing module received a number of improvements and is no longer provisional.
The tracemalloc module has been significantly reworked and is now used to provide better output for ResourceWarning as well as provide better diagnostics for memory allocation errors. See the PYTHONMALLOC section for more information.
Security improvements:
The new secrets module has been added to simplify the generation of cryptographically strong pseudo-random numbers suitable for managing secrets such as account authentication, tokens, and similar.
On Linux, os.urandom() now blocks until the system urandom entropy pool is initialized to increase the security. See the PEP 524 for the rationale.
The hashlib and ssl modules now support OpenSSL 1.1.0.
The default settings and feature set of the ssl module have been improved.
The hashlib module received support for the BLAKE2, SHA-3 and SHAKE hash algorithms and the scrypt() key derivation function.
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