C API from Extension Module in Python | Set 2

C API from Extension Module in Python | Set 2

Last Updated : 27 Mar, 2019

Prerequisite: C API from Extension Module in Python | Set 1 Let's see an example of a new extension module that loads and uses these API functions that we build up in the previous article. Code #1 :

C

#include "pythonsample.h"
/* An extension function that uses the exported API */
static PyObject *print_point(PyObject *self, PyObject *args)
{
    PyObject *obj;
    Point *p;
    if (!PyArg_ParseTuple(args, "O", &obj))
    {
        return NULL;
    }
    /* Note: This is defined in a different module */
    p = PyPoint_AsPoint(obj);
    if (!p)
    {
        return NULL;
    }
    printf("%f %f\n", p->x, p->y);
    return Py_BuildValue("");
}

static PyMethodDef PtExampleMethods[] =
{
    {"print_point", print_point, METH_VARARGS, "output a point"},
    { NULL, NULL, 0, NULL}
};

static struct PyModuleDef ptexamplemodule =
{
    PyModuleDef_HEAD_INIT,
    /* name of module */
    "ptexample", 
    /* Doc string (may be NULL) */
    "A module that imports an API", 
    /* Size of per-interpreter state or -1 */
    -1, 
    /* Method table */
    PtExampleMethods 
    
};

Code #2 : Module initialization function

C

PyMODINIT_FUNC
PyInit_ptexample(void)
{
    PyObject *m;
    
    m = PyModule_Create(&ptexamplemodule);
    
    if (m == NULL)
        return NULL;
    
    /* Import sample, loading its API functions */
    if (!import_sample())
    {
        return NULL;
    }
    
    return m;
}

Now to compile this new module, one need not bother about how to link against any of the libraries or code from the other module. One can just simply use work.py file as shown below. Code #3 :

Python3 1==

# setup.py
from distutils.core import setup, Extension

# May need pythonsample.h directory
setup(name ='ptexample', 
      ext_modules = [ Extension('ptexample', 
                     ['ptexample.c'], include_dirs = [], )])

After performing all this task, this new extension function works perfectly with the C API functions defined in the other module. Code #4 : Using CPI API functions defined in the other module

Python3 1==

import ptexample
import work

point1 = work.Point(2, 3)
print ("Point_1 : ", point1)

print ("\n", ptexample.print_point(p1))

Output :

Point_1 : 

2.000000 3.000000

C API from Extension Module in Python | Set 2

M

manikachandna97

Improve

Article Tags :

Practice Tags :

python

Similar Reads

C API from Extension Module in Python | Set 1

Suppose given a C extension module that internally defines a variety of useful functions that can be exported as a public C API for use elsewhere. Now if we want to use these functions inside other extension modules. Then, it is important to know how to link them together but doing it with the C com

C Extension Module using Python

Writing a simple C extension module directly using Pythonâ€™s extension API and no other tools. It is straightforward to make a handcrafted extension module for a simple C code. But first, we have to make sure that the C code has a proper header file. Code #1 : C #include <math.h> extern int gcd

How to create modules in Python 3 ?

Modules are simply python code having functions, classes, variables. Any python file with .py extension can be referenced as a module. Although there are some modules available through the python standard library which are installed through python installation, Other modules can be installed using t

Create and Import modules in Python

In Python, a module is a self-contained Python file that contains Python statements and definitions, like a file named GFG.py, can be considered as a module named GFG which can be imported with the help of import statement. However, one might get confused about the difference between modules and pac

Introduction to Python Typing-Extensions Module

The typing-extensions module provides backports of the latest typing features to ensure that developers working with older versions of Python can still leverage these advanced tools. This module acts as a bridge between future releases of Python and existing codebases, enabling us to stay up to date

Python | Passing Filenames to Extension in C

Filename has to be encoded according to the systemâ€™s expected filename encoding before passing filenames to C library functions. Code #1 : To write an extension function that receives a filename CPP static PyObject* py_get_filename(PyObject* self, PyObject* args) { PyObject* bytes; char* filename; P

Python | Opaque Pointers in C extension modules

Let's discuss an extension module that needs to handle a pointer to a C data structure, without exposing any internal details of the structure to Python. Opaque data structures can be easily handled by wrapping them inside capsule objects as shown in the code snippet below. Code #1 : C typedef struc

Calling Python from C | Set 2

Prerequisite: Calling Python from C | Set 1 A reference to an existing Python callable needs to be passed in, to use this function. To do that there are many ways like â€“ simply writing C code to extract a symbol from an existing module or having a callable object passed into an extension module. Cod

Change File Extension In Python

Changing file extensions in Python can be a common task when working with files. Whether you need to modify file types for compatibility, organize your files, or perform some other operation, Python provides several methods to achieve this. In this article, we will explore four different methods to

How to get file extension in Python?

In this article, we will cover How to extract file extensions using Python. How to Get File Extension in Python? Get File Extension in Python we can use either of the two different approaches discussed below: Use the os.path Module to Extract Extension From File in PythonUse the pathlib Module to Ex