Various methods of Python calling C + +

Various methods of Python calling C + +

2010-12-07 09:59 28433 People read reviews (1) Favorites

Python is an explanatory language, the bottom is implemented in C, so it is very easy to call C with Python, the following summarizes the various methods of invocation, give examples, all the examples are ubuntu9.10, python2.6 under the test.

1. Python calls C (base)

Want to call C functions in Python, like here's fact

#include <Python.h>

int fact (int n)

{

if (n <= 1)

return 1;

Else

return n * fact (n-1);

}

pyobject* wrap_fact (pyobject* self, pyobject* args)

{

int n, result;

if (! Pyarg_parsetuple (args, "i:fact", &n))

return NULL;

result = fact (n);

Return Py_buildvalue ("I", result);

}

Static Pymethoddef examplemethods[] =

{

{"Fact", Wrap_fact, Meth_varargs, "Caculate n!"},

{NULL, NULL}

};

void Initexample ()

{

pyobject* m;

m = Py_initmodule ("Example", examplemethods);

}

Save this piece of code as a wrapper.c and make it into so library,

Gcc-fpic Wrapper.c-o Example.so-shared-i/usr/include/python2.6-i/usr/lib/python2.6/config

Then, in the directory with this so library, go to Python, you can use the following

Import Example

Example.fact (4)

2. Python calls C + + (base)

Call C + + class member functions in Python, such as the fact function in the Testfact class,

#include <Python.h>

Class testfact{

Public

Testfact () {};

~testfact () {};

int fact (int n);

};

int testfact::fact (int n)

{

if (n <= 1)

return 1;

Else

return n * (n-1);

}

int fact (int n)

{

Testfact T;

return T.fact (n);

}

pyobject* wrap_fact (pyobject* self, pyobject* args)

{

int n, result;

if (! Pyarg_parsetuple (args, "i:fact", &n))

return NULL;

result = fact (n);

Return Py_buildvalue ("I", result);

}

Static Pymethoddef examplemethods[] =

{

{"Fact", Wrap_fact, Meth_varargs, "Caculate n!"},

{NULL, NULL}

};

extern "C"//does not cause initexample to be found

void Initexample ()

{

pyobject* m;

m = Py_initmodule ("Example", examplemethods);

}

Save this piece of code as a wrapper.cpp and make it into so library,

g++-fpic Wrapper.cpp-o Example.so-shared-i/usr/include/python2.6-i/usr/lib/python2.6/config

Then, in the directory with this so library, go to Python, you can use the following

Import Example

Example.fact (4)

3. Python calls C + + (Boost.python)

The boost library is a very powerful library in which the Python library can be used to encapsulate C + + being called by Python and is powerful enough not only to encapsulate functions but also to encapsulate classes, class members.

Http://dev.gameres.com/Program/Abstract/Building%20Hybrid%20Systems%20with%20Boost_Python.CHN.by.JERRY.htm

First install Boost.python under Ubuntu, Apt-get installs Libboost-python-dev

#include <boost/python.hpp>

Char const* greet ()

{

Return "Hello, World";

}

Boost_python_module (Hello)

{

Using namespace boost::p Ython;

def ("greet", greet);

}

Save the code as hello.cpp and compile it into so library

g++ Hello.cpp-o Hello.so-shared-i/usr/include/python2.5-i/usr/lib/python2.5/config-lboost_python-gcc42-mt-1_34_1

Here the Python path is set to your Python path, and must be-lboost_python-gcc42-mt-1_34_1, this library name is not necessarily this, go to/user/lib

Then, in the directory with this so library, go to Python, you can use the following

>>> Import Hello

>>> Hello.greet ()

' Hello, World '

4. Python calls C + + (ctypes)

cTYPES is a advanced FFI (Foreign Function Interface) package for Python 2.3 and higher. In Python 2.5 It is already included.

cTYPES allows to call functions in dlls/shared libraries and have extensive facilities to create, access and manipulate sim Ple and complicated C data types in python-in other words:wrap libraries in pure Python. It is even possible to implement C callback functions in pure Python.

http://python.net/crew/theller/ctypes/

#include <Python.h>

Class testfact{

Public

Testfact () {};

~testfact () {};

int fact (int n);

};

int testfact::fact (int n)

{

if (n <= 1)

return 1;

Else

return n * (n-1);

}

extern "C"

int fact (int n)

{

Testfact T;

return T.fact (n);

}

Save the code as wrapper.cpp do not write Python interface encapsulation, directly compiled into so library,

g++-fpic Wrapper.cpp-o Example.so-shared-i/usr/include/python2.6-i/usr/lib/python2.6/config

To enter Python, you can use the following

>>> Import cTYPES

>>> Pdll = ctypes. Cdll ('/home/ubuntu/tmp/example.so ')

>>> Pdll.fact (4)

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Various methods of Python calling C + +