how avoid delay while returning from C-python api?
Stefan Behnel
stefan_ml at behnel.de
Wed May 28 15:00:54 EDT 2014
Lakshmipathi.G, 28.05.2014 12:22:
> I have C-Python api like below. It works fine, but the problem is
> while invoking this method
> from python script say
>
> #cat script.py
> <snip>
> offset=0
> size=4
> write_object(offset,size)
> </snip>
>
>
> This calls write_this_c() C api and returns quickly to next printf statement.
> But the return call (Py_RETURN_NONE) takes something like 4-6 seconds.
>
> -----
> static
> PyMethodDef xyz_methods[] = {
> {"write_object", write_object, METH_VARARGS,"write some stuff "},
> {NULL, NULL, 0, NULL}
> };
>
>
> ----
> static PyObject *
> write_object(PyObject *self, PyObject *args)
> {
> int offset, size;
> if (!PyArg_ParseTuple(args,"ii", &offset, &size))
> Py_RETURN_NONE;
>
> printf("before call");
> write_this_c(offset, size);
> printf("after call");
> Py_RETURN_NONE; ##delay happens here
> }
>
> How to avoid this delay time? Thanks for any help/pointers!
You already found the problem yourself, so let me just give you a general
advice that you can avoid a lot of the hassle of writing code like the
above and struggling to get it right by writing it in Cython instead of
plain C. Here's a complete example of the above code in Cython, including
the module setup code etc., but without the bugs:
# external declarations:
cdef extern from "someheader.h":
void write_this_c(int offset, int size)
# your module function:
def write_object(int offset, int size):
"""write some stuff"""
print("before call")
write_this_c(offset, size)
print("after call")
That's it.
Stefan
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