[Cython] Cython 0.21 released
stefan_ml at behnel.de
Wed Sep 10 18:40:37 CEST 2014
on behalf of the Cython dev team, I'm pleased to announce the release of
Cython 0.21, a major feature release. Thanks everyone who contributed code,
documentation improvements, test feedback, bug reports and/or otherwise
helpful insights for this release.
I copied the complete changelog of this release below, but here are the
major highlights, in addition to the many bug fixes and general
improvements in this release.
* Legacy code and support for old CPython versions was removed, baselines
are now Python 2.6 and 3.2.
* cdef functions finally support inner Python functions with closures.
* C enums can now be declared as "cpdef" to publish them to Python space.
* Python method calls, boolean "and/or" operators and cascaded assignments
were optimised to streamline calls and type coercions.
* The annotated HTML code output is syntax highlighted and beautified.
* C (cdef) functions allow inner Python functions.
* Enums can now be declared as cpdef to export their values to
the module's Python namespace. Cpdef enums in pxd files export
their values to their own module, iff it exists.
* Allow @staticmethod decorator to declare static cdef methods.
This is especially useful for declaring "constructors" for
cdef classes that can take non-Python arguments.
* Taking a ``char*`` from a temporary Python string object is safer
in more cases and can be done inside of non-trivial expressions,
including arguments of a function call. A compile time error
is raised only when such a pointer is assigned to a variable and
would thus exceed the lifetime of the string itself.
* Generators have new properties ``__name__`` and ``__qualname__``
that provide the plain/qualified name of the generator function
(following CPython 3.5). See http://bugs.python.org/issue21205
* The ``inline`` function modifier is available as a decorator
``@cython.inline`` in pure mode.
* When cygdb is run in a virtualenv, it enables the same virtualenv
inside of the debugger. Patch by Marc Abramowitz.
* PEP 465: dedicated infix operator for matrix multiplication (A @ B).
* HTML output of annotated code uses Pygments for code highlighting
and generally received a major overhaul by Matthias Bussonier.
* IPython magic support is now available directly from Cython with
the command "%load_ext cython". Cython code can directly be
executed in a cell when marked with "%%cython". Code analysis
is available with "%%cython -a". Patch by Martín Gaitán.
* Simple support for declaring Python object types in Python signature
annotations. Currently requires setting the compiler directive
* New directive ``use_switch`` (defaults to True) to optionally disable
the optimization of chained if statement to C switch statements.
* Defines dynamic_cast et al. in ``libcpp.cast`` and C++ heap data
structure operations in ``libcpp.algorithm``.
* Shipped header declarations in ``posix.*`` were extended to cover
more of the POSIX API. Patches by Lars Buitinck and Mark Peek.
* Simple calls to C implemented Python functions/methods are faster.
This also speeds up many operations on builtins that Cython cannot
* The "and"/"or" operators try to avoid unnecessary coercions of their
arguments. They now evaluate the truth value of each argument
independently and only coerce the final result of the whole expression
to the target type (e.g. the type on the left side of an assignment).
This also avoids reference counting overhead for Python values during
evaluation and generally improves the code flow in the generated C code.
* The Python expression "2 ** N" is optimised into bit shifting.
* Cascaded assignments (a = b = ...) try to minimise the number of
* Calls to ``slice()`` are translated to a straight C-API call.
* Crash when assigning memory views from ternary conditional expressions.
* Nested C++ templates could lead to unseparated ">>" characters being
generated into the C++ declarations, which older C++ compilers could
* Sending SIGINT (Ctrl-C) during parallel cythonize() builds could
hang the child processes.
* No longer ignore local setup.cfg files for distutils in pyximport.
Patch by Martin Teichmann.
* Taking a ``char*`` from an indexed Python string generated unsafe
reference counting code.
* Set literals now create all of their items before trying to add them
to the set, following the behaviour in CPython. This makes a
difference in the rare case that the item creation has side effects
and some items are not hashable (or if hashing them has side effects,
* Cython no longer generates the cross product of C functions for code
that uses memory views of fused types in function signatures (e.g.
``cdef func(floating[:] a, floating[:] b)``). This is considered the
expected behaviour by most users and was previously inconsistent with
other structured types like C arrays. Code that really wants all type
combinations can create the same fused memoryview type under different
names and use those in the signature to make it clear which types are
* Names that were unknown at compile time were looked up as builtins at
runtime but not as global module names. Trying both lookups helps with
* Fixed stl container conversion for typedef element types.
* ``obj.pop(x)`` truncated large C integer values of x to ``Py_ssize_t``.
* ``__init__.pyc`` is recognised as marking a package directory
(in addition to .py, .pyx and .pxd).
* Syntax highlighting in ``cython-mode.el`` for Emacs no longer
incorrectly highlights keywords found as part of longer names.
* Correctly handle ``from cython.submodule cimport name``.
* Fix infinite recursion when using super with cpdef methods.
* No-args ``dir()`` was not guaranteed to return a sorted list.
* The header line in the generated C files no longer contains the
timestamp but only the Cython version that wrote it. This was
changed to make builds more reproducible.
* Removed support for CPython 2.4, 2.5 and 3.1.
* The licensing implications on the generated code were clarified
to avoid legal constraints for users.
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