mirror of
https://github.com/kennethreitz/python-guide.git
synced 2026-06-05 23:00:18 +00:00
aaron
107 lines
3.2 KiB
ReStructuredText
107 lines
3.2 KiB
ReStructuredText
Interfacing with C/C++ Libraries
|
|
================================
|
|
|
|
|
|
ctypes
|
|
------
|
|
|
|
`ctypes <https://docs.python.org/3/library/ctypes.html>`_ is the de facto
|
|
library for interfacing with C/C++, and it provides not only full access to
|
|
the native C interface of most major operating systems (e.g., kernel32 on
|
|
Windows, or libc on *nix), but also provides support for loading and
|
|
interfacing with dynamic libraries, such as DLLs or shared objects at runtime.
|
|
It does bring along with it a whole host of types for interacting with system
|
|
APIs, and allows you to rather easily define your own complex types, such
|
|
as structs and unions, and allows you to modify things such as padding and
|
|
alignment, if needed. It can be a bit crufty to use, but in conjunction with
|
|
the `struct <https://docs.python.org/3.5/library/struct.html>`_ module, you
|
|
are essentially provided full control over how your data types get translated
|
|
into something something usable by a C(++).
|
|
|
|
Struct Equivalents
|
|
~~~~~~~~~~~~~~~~~~
|
|
|
|
:file:`MyStruct.h`
|
|
|
|
.. code-block:: c
|
|
:linenos:
|
|
|
|
struct my_struct {
|
|
int a;
|
|
int b;
|
|
};
|
|
|
|
:file:`MyStruct.py`
|
|
|
|
.. code-block:: python
|
|
:linenos:
|
|
|
|
import ctypes
|
|
class my_struct(ctypes.Structure):
|
|
_fields_ = [("a", c_int),
|
|
("b", c_int)]
|
|
|
|
SWIG
|
|
----
|
|
|
|
`SWIG <http://www.swig.org>`_, though not strictly Python focused (it supports a
|
|
large number of scripting languages), is a tool for generating bindings for
|
|
interpreted languages from C/C++ header files. It is extremely simple to use:
|
|
the consumer simply needs to define an interface file (detailed in the
|
|
tutorial and documentations), include the requisite C/C++ headers, and run
|
|
the build tool against them. While it does have some limits, (it currently
|
|
seems to have issues with a small subset of newer C++ features, and getting
|
|
template-heavy code to work can be a bit verbose), it provides a great deal
|
|
of power and exposes lots of features to Python with little effort.
|
|
Additionally, you can easily extend the bindings SWIG creates (in the
|
|
interface file) to overload operators and built-in methods, effectively re-
|
|
cast C++ exceptions to be catchable by Python, etc.
|
|
|
|
Example: Overloading __repr__
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
:file:`MyClass.h`
|
|
|
|
.. code-block:: c++
|
|
:linenos:
|
|
|
|
#include <string>
|
|
class MyClass {
|
|
private:
|
|
std::string name;
|
|
public:
|
|
std::string getName();
|
|
};
|
|
|
|
:file:`myclass.i`
|
|
|
|
.. code-block:: c++
|
|
:linenos:
|
|
|
|
%include "string.i"
|
|
|
|
%module myclass
|
|
%{
|
|
#include <string>
|
|
#include "MyClass.h"
|
|
%}
|
|
|
|
%extend MyClass {
|
|
std::string __repr__()
|
|
{
|
|
return $self->getName();
|
|
}
|
|
}
|
|
|
|
%include "MyClass.h"
|
|
|
|
|
|
Boost.Python
|
|
------------
|
|
|
|
`Boost.Python <http://www.boost.org/doc/libs/1_59_0/libs/python/doc/>`_
|
|
requires a bit more manual work to expose C++ object functionality, but
|
|
it is capable of providing all the same features SWIG does, and then some,
|
|
to include providing wrappers to access PyObjects in C++, extracting SWIG-
|
|
wrapper objects, and even embedding bits of Python into your C++ code.
|