0.28 (2018-03-13)

Features added

  • Cdef classes can now multiply inherit from ordinary Python classes.(The primary base must still be a c class, possibly object, andthe other bases must not be cdef classes.)
  • Type inference is now supported for Pythran compiled NumPy expressions.Patch by Nils Braun. (Github issue #1954)
  • The const modifier can be applied to memoryview declarations to allowread-only buffers as input. (Github issues #1605, #1869)
  • C code in the docstring of a cdef extern block is copied verbatimlyinto the generated file.Patch by Jeroen Demeyer. (Github issue #1915)
  • When compiling with gcc, the module init function is now tuned for smallcode size instead of whatever compile flags were provided externally.Cython now also disables some code intensive optimisations in that functionto further reduce the code size. (Github issue #2102)
  • Decorating an async coroutine with @cython.iterable_coroutine changes itstype at compile time to make it iterable. While this is not strictly in linewith PEP-492, it improves the interoperability with old-style coroutines thatuse yield from instead of await.
  • The IPython magic has preliminary support for JupyterLab.(Github issue #1775)
  • The new TSS C-API in CPython 3.7 is supported and has been backported.Patch by Naotoshi Seo. (Github issue #1932)
  • Cython knows the new Py_tss_t type defined in PEP-539 and automaticallyinitialises variables declared with that type to Py_tss_NEEDS_INIT,a value which cannot be used outside of static assignments.
  • The set methods .remove() and .discard() are optimised.Patch by Antoine Pitrou. (Github issue #2042)
  • dict.pop() is optimised.Original patch by Antoine Pitrou. (Github issue #2047)
  • Iteration over sets and frozensets is optimised.(Github issue #2048)
  • Safe integer loops (< range(2^30)) are automatically optimised into C loops.
  • alist.extend([a,b,c]) is optimised into sequential list.append() callsfor short literal sequences.
  • Calls to builtin methods that are not specifically optimised into C-API callsnow use a cache that avoids repeated lookups of the underlying C function.(Github 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 forloop optimisations.
  • Indexing into memoryview slices with view[i][j] is now optimised intoview[i, j].
  • Python compatible cython.* types can now be mixed with type declarationsin Cython syntax.
  • Name lookups in the module and in classes are faster.
  • Python attribute lookups on extension types without instance dict are faster.
  • Some missing signals were added to libc/signal.pxd.Patch by Jeroen Demeyer. (Github issue #1914)
  • The warning about repeated extern declarations is now visible by default.(Github issue #1874)
  • The exception handling of the function types used by CPython’s type slotfunctions was corrected to match the de-facto standard behaviour, so thatcode that uses them directly benefits from automatic and correct exceptionpropagation. Patch by Jeroen Demeyer. (Github issue #1980)
  • Defining the macro CYTHON_NO_PYINIT_EXPORT will prevent the module initfunction from being exported as symbol, e.g. when linking modules staticallyin an embedding setup. Patch by AraHaan. (Github issue #1944)

Bugs fixed

  • If a module name is explicitly provided for an Extension() that is compiledvia cythonize(), it was previously ignored and replaced by the source filename. It can now be used to override the target module name, e.g. for compilingprefixed accelerator modules from Python files. (Github issue #2038)
  • The arguments of the num_threads parameter of parallel sectionswere not sufficiently validated and could lead to invalid C code.(Github issue #1957)
  • Catching exceptions with a non-trivial exception pattern could call intoCPython with a live exception set. This triggered incorrect behaviourand crashes, especially in CPython 3.7.
  • The signature of the special richcmp() method was corrected to recognisethe type of the first argument as self. It was previously treated as plainobject, but CPython actually guarantees that it always has the correct type.Note: this can change the semantics of user code that previously relied onself being untyped.
  • Some Python 3 exceptions were not recognised as builtins when running Cythonunder Python 2.
  • Some async helper functions were not defined in the generated C code whencompiling simple async code. (Github issue #2075)
  • Line tracing did not include generators and coroutines.(Github issue #1949)
  • C++ declarations for unordered_map were corrected.Patch by Michael Schatzow. (Github issue #1484)
  • Iterator declarations in C++ deque and vector were corrected.Patch by Alex Huszagh. (Github issue #1870)
  • The const modifiers in the C++ string declarations were corrected, togetherwith the coercion behaviour of string literals into C++ strings.(Github issue #2132)
  • Some declaration types in libc.limits were corrected.Patch by Jeroen Demeyer. (Github issue #2016)
  • @cython.final was not accepted on Python classes with an @cython.cclassdecorator. (Github issue #2040)
  • Cython no longer creates useless and incorrect PyInstanceMethod wrappers formethods in Python 3. Patch by Jeroen Demeyer. (Github issue #2105)
  • The builtin bytearray type could not be used as base type of cdef classes.(Github issue #2106)

Other changes