Release Date: June 18, 2019

Python 3.7.4rc1 is the release candidate preview of the fourth maintenance release of Python 3.7. The Python 3.7 series is the newest major release of the Python language and contains many new features and optimizations.

Note that 3.7.4rc1 is a release preview and thus its use is not recommended for production environments.

Among the major new features in Python 3.7 are:

• PEP 539, new C API for thread-local storage
• PEP 545, Python documentation translations
• New documentation translations: Japanese, French, and Korean.
• PEP 552, Deterministic pyc files
• PEP 553, Built-in breakpoint()
• PEP 557, Data Classes
• PEP 560, Core support for typing module and generic types
• PEP 562, Customization of access to module attributes
• PEP 563, Postponed evaluation of annotations
• PEP 564, Time functions with nanosecond resolution
• PEP 565, Improved DeprecationWarning handling
• PEP 567, Context Variables
• Avoiding the use of ASCII as a default text encoding (PEP 538, legacy C locale coercion and PEP 540, forced UTF-8 runtime mode)
• The insertion-order preservation nature of dict objects is now an official part of the Python language spec.
• Notable performance improvements in many areas.

Please see What’s New In Python 3.7 for more information.

Full Changelog