Cython v0.28 Release Notes

Release Date: 2018-03-13 // over 3 years ago
  • ๐Ÿ”‹ Features added

    • Cdef classes can now multiply inherit from ordinary Python classes. (The primary base must still be a c class, possibly object, and the other bases must not be cdef classes.)

    • ๐Ÿ‘ Type inference is now supported for Pythran compiled NumPy expressions. Patch by Nils Braun. (Github issue :issue:1954)

    • The const modifier can be applied to memoryview declarations to allow read-only buffers as input. (Github issues :issue:1605, :issue:1869)

    • ๐Ÿ“„ C code in the docstring of a cdef extern block is copied verbatimly into the generated file. Patch by Jeroen Demeyer. (Github issue :issue:1915)

    • When compiling with gcc, the module init function is now tuned for small code size instead of whatever compile flags were provided externally. Cython now also disables some code intensive optimisations in that function to further reduce the code size. (Github issue :issue:2102)

    • Decorating an async coroutine with @cython.iterable_coroutine changes its type at compile time to make it iterable. While this is not strictly in line with PEP-492, it improves the interoperability with old-style coroutines that use yield from instead of await.

    • ๐Ÿ‘ The IPython magic has preliminary support for JupyterLab. (Github issue :issue:1775)

    • ๐Ÿ‘ The new TSS C-API in CPython 3.7 is supported and has been backported. Patch by Naotoshi Seo. (Github issue :issue:1932)

    • Cython knows the new Py_tss_t type defined in PEP-539 and automatically initialises variables declared with that type to Py_tss_NEEDS_INIT, a value which cannot be used outside of static assignments.

    • ๐Ÿšš The set methods .remove() and .discard() are optimised. Patch by Antoine Pitrou. (Github issue :issue:2042)

    • dict.pop() is optimised. Original patch by Antoine Pitrou. (Github issue :issue:2047)

    • Iteration over sets and frozensets is optimised. (Github issue :issue:2048)

    • Safe integer loops (< range(230)) are automatically optimised into C loops.

    • alist.extend([a,b,c]) is optimised into sequential list.append() calls for short literal sequences.

    • Calls to builtin methods that are not specifically optimised into C-API calls now use a cache that avoids repeated lookups of the underlying C function. (Github issue :issue:2054)

    • Single argument function calls can avoid the argument tuple creation in some cases.

    • Some redundant extension type checks are avoided.

    • Formatting C enum values in f-strings is faster, as well as some other special cases.

    • String formatting with the '%' operator is optimised into f-strings in simple cases.

    • Subscripting (item access) is faster in some cases.

    • Some bytearray operations have been optimised similar to bytes.

    • Some PEP-484/526 container type declarations are now considered for loop optimisations.

    • Indexing into memoryview slices with view[i][j] is now optimised into view[i, j].

    • Python compatible cython.* types can now be mixed with type declarations in Cython syntax.

    • Name lookups in the module and in classes are faster.

    • Python attribute lookups on extension types without instance dict are faster.

    • ๐Ÿšฆ Some missing signals were added to libc/signal.pxd. Patch by Jeroen Demeyer. (Github issue :issue:1914)

    • โš  The warning about repeated extern declarations is now visible by default. (Github issue :issue:1874)

    • ๐Ÿ‘ป The exception handling of the function types used by CPython's type slot functions was corrected to match the de-facto standard behaviour, so that code that uses them directly benefits from automatic and correct exception propagation. Patch by Jeroen Demeyer. (Github issue :issue:1980)

    • Defining the macro CYTHON_NO_PYINIT_EXPORT will prevent the module init function from being exported as symbol, e.g. when linking modules statically in an embedding setup. Patch by AraHaan. (Github issue :issue:1944)

    ๐Ÿ› Bugs fixed

    • If a module name is explicitly provided for an Extension() that is compiled via cythonize(), it was previously ignored and replaced by the source file name. It can now be used to override the target module name, e.g. for compiling prefixed accelerator modules from Python files. (Github issue :issue:2038)

    • The arguments of the num_threads parameter of parallel sections were not sufficiently validated and could lead to invalid C code. (Github issue :issue:1957)

    • ๐Ÿ‘ป Catching exceptions with a non-trivial exception pattern could call into CPython with a live exception set. This triggered incorrect behaviour and crashes, especially in CPython 3.7.

    • The signature of the special __richcmp__() method was corrected to recognise the type of the first argument as self. It was previously treated as plain object, but CPython actually guarantees that it always has the correct type. Note: this can change the semantics of user code that previously relied on self being untyped.

    • Some Python 3 exceptions were not recognised as builtins when running Cython under Python 2.

    • Some async helper functions were not defined in the generated C code when compiling simple async code. (Github issue :issue:2075)

    • Line tracing did not include generators and coroutines. (Github issue :issue:1949)

    • C++ declarations for unordered_map were corrected. Patch by Michael Schatzow. (Github issue :issue:1484)

    • Iterator declarations in C++ deque and vector were corrected. Patch by Alex Huszagh. (Github issue :issue:1870)

    • The const modifiers in the C++ string declarations were corrected, together with the coercion behaviour of string literals into C++ strings. (Github issue :issue:2132)

    • Some declaration types in libc.limits were corrected. Patch by Jeroen Demeyer. (Github issue :issue:2016)

    • @cython.final was not accepted on Python classes with an @cython.cclass decorator. (Github issue :issue:2040)

    • Cython no longer creates useless and incorrect PyInstanceMethod wrappers for methods in Python 3. Patch by Jeroen Demeyer. (Github issue :issue:2105)

    • The builtin bytearray type could not be used as base type of cdef classes. (Github issue :issue:2106)

    Other changes