[SciPy-User] ANN: Cython 0.13 released!

Dag Sverre Seljebotn dagss@student.matnat.uio...
Wed Aug 25 03:04:50 CDT 2010

Forwarding; Crag Citro wrote:

It is with *great* pleasure that I email to announce the release of
Cython version 0.13! This release sets another milestone on the path
towards Python compatibility and brings major new features and
improvements for the usability of the Cython language.

 Download it here: http://cython.org/release/Cython-0.13.tar.gz

== New Features ==

 * Closures are fully supported for Python functions. Cython supports
inner functions and lambda expressions. Generators and generator
expressions are __not__ supported in this release.

 * Proper C++ support. Cython knows about C++ classes, templates and
overloaded function signatures, so that Cython code can interact with
them in a straight forward way.

 * Type inference is enabled by default for safe C types (e.g. double,
bint, C++ classes) and known extension types. This reduces the need
for explicit type declarations and can improve the performance of
untyped code in some cases. There is also a verbose compile mode for
testing the impact on user code.

 * Cython's for-in-loop can iterate over C arrays and sliced pointers.
The type of the loop variable will be inferred automatically in this

 * The Py_UNICODE integer type for Unicode code points is fully
supported, including for-loops and 'in' tests on unicode strings. It
coerces from and to single character unicode strings. Note that
untyped for-loop variables will automatically be inferred as
Py_UNICODE when iterating over a unicode string. In most cases, this
will be much more efficient than yielding sliced string objects, but
can also have a negative performance impact when the variable is used
in a Python context multiple times, so that it needs to coerce to a
unicode string object more than once. If this happens, typing the loop
variable as unicode or object will help.

 * The built-in functions any(), all(), sum(), list(), set() and
dict() are inlined as plain `for` loops when called on generator
expressions. Note that generator expressions are not generally
supported apart from this feature. Also, tuple(genexpr) is not
currently supported - use tuple([listcomp]) instead.

 * More shipped standard library declarations. The python_* and
stdlib/stdio .pxd files have been deprecated in favor of clib.* and
cpython[.*] and may get removed in a future release.

== Python compatibility ==

 * Pure Python mode no longer disallows non-Python keywords like
'cdef', 'include' or 'cimport'. It also no longer recognises syntax
extensions like the for-from loop.

 * Parsing has improved for Python 3 syntax in Python code, although
not all features are correctly supported. The missing Python 3
features are being worked on for the next release.

 * from __future__ import print_function is supported in Python 2.6
and later. Note that there is currently no emulation for earlier
Python versions, so code that uses print() with this future import
will require at least Python 2.6.

 * New compiler directive language_level (valid values: 2 or 3) with
corresponding command line options -2 and -3 requests source code
compatibility with Python 2.x or Python 3.x respectively. Language
level 3 currently enforces unicode literals for unprefixed string
literals, enables the print function (requires Python 2.6 or later)
and keeps loop variables in list comprehensions from leaking.

 * Loop variables in set/dict comprehensions no longer leak into the
surrounding scope (following Python 2.7). List comprehensions are
unchanged in language level 2.

== Incompatible changes ==

 * The availability of type inference by default means that Cython
will also infer the type of pointers on assignments. Previously, code
like this

 cdef char* s = ...
 untyped_variable = s

 would convert the char* to a Python bytes string and assign that.
This is no longer the case and no coercion will happen in the example
above. The correct way of doing this is through an explicit cast or by
typing the target variable, i.e.

 cdef char* s = ...
 untyped_variable1 = <bytes>s
 untyped_variable2 = <object>s

 cdef object py_object = s
 cdef bytes  bytes_string = s

 * bool is no longer a valid type name by default. The problem is that
it's not clear whether bool should refer to the Python type or the C++
type, and expecting one and finding the other has already led to
several hard-to-find bugs. Both types are available for importing: you
can use from cpython cimport bool for the Python bool type, and from
libcpp cimport bool for the C++ type.

== Contributors ==

Many people contributed to this release, including:

 * David Barnett
 * Stefan Behnel
 * Chuck Blake
 * Robert Bradshaw
 * Craig Citro
 * Bryan Cole
 * Lisandro Dalcin
 * Eric Firing
 * Danilo Freitas
 * Christoph Gohlke
 * Dag Sverre Seljebotn
 * Kurt Smith
 * Erik Tollerud
 * Carl Witty

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