call c function from python

Question

I have code in c :

typedef struct {
int bottom;
int top;
int left;
int right;
} blur_rect;

int bitmapblur(
char* input,
char* output,
blur_rect* rects,
int count,
int blur_repetitions);

I need use the bitmapblur function from python . How I do it? The question about array of structs.

THX

The question is "HOW CREATE ARRAY OF STRUCTS IN PYTON???????" — Leonid
– Leonid, Commented Jun 16, 2012 at 17:00

EyalAr · Accepted Answer · 2012-06-16 16:56:38Z

5

you will need to compile your c code as a shared library and then use the 'ctypes' python module to interact with the library.
I recommend you start here.

answered Jun 16, 2012 at 16:56

EyalAr

3,1801 gold badge24 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

David · Accepted Answer · 2012-06-16 17:00:09Z

0

This can be usefull too: "Extending Python with C or C++", starting with a simple example. U can find more about it here.

answered Jun 16, 2012 at 17:00

David

3881 silver badge14 bronze badges

Comments

Cory · Accepted Answer · 2012-06-16 18:15:07Z

You will first need to use ctypes. First, build a struct:

import ctypes

class BlurRect(ctypes.Structure):
    """
    rectangular area to blur
    """
    _fields_ = [("bottom", ctypes.c_int),
                ("top", ctypes.c_int),
                ("left", ctypes.c_int),
                ("right", ctypes.c_int),
                ]

Now load your function. You will need to figure out the best name for the shared library, and then load it. You should have this code already implemented as a dll or .so and available in the ld path.

The other tricky bit is your function has an "output" parameter, and the function is expected to write its result there. You will need to create a buffer for that.

The ctypes code will look something like this:

blurlib = ctypes.cdll.LoadLibrary("libblur.so")
outbuf = ctypes.create_string_buffer(1024) # not sure how big you need this

inputStructs = [BlurRect(*x) for x in application_defined_data]

successFlag = blurlib.bitmapblur("input", 
    outbuf,
    inputStructs,
    count,
    reps)

Collectives™ on Stack Overflow

call c function from python

3 Answers 3

Comments

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Related