The new memoryview implementation comprehensively fixes all ownership and lifetime issues of dynamically allocated fields in the Py_buffer struct that led to multiple crash reports. Additionally, several functions that crashed or returned incorrect results for non-contiguous or multi-dimensional input have been fixed.
There are also some major performance improvements, thanks to PEP 393, which changed the Unicode string type to support multiple internal representations, allowing for space-efficient representation in most cases, while still providing access to full UCS-4 on all systems.
Other changes thanks to PEP 393 include:
- Provides full support of all Unicode code points, including non-BMP ones.
- Eliminates narrow builds, even in Windows, and thereby eliminates narrow build-specific problems.
The following features are also new to Python 3.3:
- All native single character format specifiers in struct module syntax (optionally prefixed with '@') are now supported.
- Multi-dimensional list representations are supported for any array type.
- All array types are hash able if the exporting object is hash able and the view is read-only.
- API Changes
- The maximum number of dimensions is officially limited to 64.
- The representation of empty shape, strides, and sub offsets is now an empty tuple instead of None.
Other interesting improvements:
PEP 3151: Reworking the OS and IO Exception Hierarchy - exception types have been condensed down to one: OSError, while other exceptions have been kept as aliases for compatibility reasons.
PEP 409: Suppressing Exception Context - disables the display of the chained exception context, providing better error messages.
There is also a long list of New and Improved Modules for Python 3.3 you can browse through here.