pass a text file , as argument of main() in Python

[nimitsis]

Hallo everyone,
I'm trying to convert a main function from C to Python,by using Swig and call it with a .txt argument.The code is the following :

/*test.c*/
#include <stdio.h>
int main(int argc, char ** argv)
{
    float f1,f2,f3;
    FILE *fp;
    fp=fopen(argv[1],"r");
    if(fp!=NULL)
    {
        printf("Succesfull opening\n");
        fscanf(fp,"%f\n%f\n%f",&f1,&f2,&f3);
        printf("the values are \n%f\n%f\n%f\n",f1,f2,f3);
        fclose(fp);
    }
    return 0;
}
 
/*test_interface.i*/
%module example
%{
    int main(int argc,char **argv);
%}
int main(int argc,char **argv);
 
/*text.txt*/

0.2313
2.3123
12.123

from Linux command prompt I execute the following commands:

$ swig -python test_interface.i
$ gcc -c test.c test_interface_wrap.c -I/usr/include/python2.5
$ ld -shared test.o test_interface_wrap.o -o _example.so
$ python
>>>from _example import *
>>>main(1,'text1.txt') // ERROR !!!!
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: in method 'main', argument 2 of type 'char **'

All i want to do is the same thing like the following C procces:
$ gcc test.c -o test
$ ./test text.txt
the values are
0.231300
2.312300
12.123000

What is the solution?

[varuns]

Hallo everyone,
I'm trying to convert a main function from C to Python,by using Swig and call it with a .txt argument.The code is the following :

/*test.c*/
#include <stdio.h>
int main(int argc, char ** argv)
{
float f1,f2,f3;
FILE *fp;
fp=fopen(argv[1],"r");
if(fp!=NULL)
{
printf("Succesfull opening\n");
fscanf(fp,"%f\n%f\n%f",&f1,&f2,&f3);
printf("the values are \n%f\n%f\n%f\n",f1,f2,f3);
fclose(fp);
}
return 0;
}

/*test_interface.i*/
%module example
%{
int main(int argc,char **argv);
%}
int main(int argc,char **argv);

/*text.txt*/
0.2313
2.3123
12.123

from Linux command prompt I execute the following commands:

$ swig -python test_interface.i
$ gcc -c test.c test_interface_wrap.c -I/usr/include/python2.5
$ ld -shared test.o test_interface_wrap.o -o _example.so
$ python
>>>from _example import *
>>>main(1,'text1.txt') // ERROR !!!!
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: in method 'main', argument 2 of type 'char **'

All i want to do is the same thing like the following C procces:
$ gcc test.c -o test
$ ./test text.txt
the values are
0.231300
2.312300
12.123000

What is the solution?

hi
just post your test_interface_wrap.c file

varun

[nimitsis]

hallo varun
Thanks for your answer .test_interface_wrap.c is about 2.700 lines .it is helpfull to post it?

[varuns]

hallo varun
Thanks for your answer .test_interface_wrap.c is about 2.700 lines .it is helpfull to post it?

only post lines of function
SWIG_wrap_main(...) or something like that

[nimitsis]

Hallo again verun
I hope the following code of interface_wrap.c is helpful.Thank you again.

extern "C" {
#endif
SWIGINTERN PyObject *_wrap_main(PyObject *SWIGUNUSEDPARM(self), PyObject *args) {
  PyObject *resultobj = 0;
  int arg1 ;
  char **arg2 = (char **) 0 ;
  int result;
  int val1 ;
  int ecode1 = 0 ;
  void *argp2 = 0 ;
  int res2 = 0 ;
  PyObject * obj0 = 0 ;
  PyObject * obj1 = 0 ;
 
  if (!PyArg_ParseTuple(args,(char *)"OO:main",&obj0,&obj1)) SWIG_fail;
  ecode1 = SWIG_AsVal_int(obj0, &val1);
  if (!SWIG_IsOK(ecode1)) {
    SWIG_exception_fail(SWIG_ArgError(ecode1), "in method '" "main" "', argument " "1"" of type '" "int""'");
  } 
  arg1 = (int)(val1);
  res2 = SWIG_ConvertPtr(obj1, &argp2,SWIGTYPE_p_p_char, 0 |  0 );
  if (!SWIG_IsOK(res2)) {
    SWIG_exception_fail(SWIG_ArgError(res2), "in method '" "main" "', argument " "2"" of type '" "char **""'"); 
  }
  arg2 = (char **)(argp2);
  result = (int)main(arg1,arg2);
  resultobj = SWIG_From_int((int)(result));
  return resultobj;
fail:
  return NULL;
}
 
 
static PyMethodDef SwigMethods[] = {
     { (char *)"main", _wrap_main, METH_VARARGS, NULL},
     { NULL, NULL, 0, NULL }
};
 
 
/* -------- TYPE CONVERSION AND EQUIVALENCE RULES (BEGIN) -------- */
 
static swig_type_info _swigt__p_char = {"_p_char", "char *", 0, 0, (void*)0, 0};
static swig_type_info _swigt__p_p_char = {"_p_p_char", "char **", 0, 0, (void*)0, 0};
 
static swig_type_info *swig_type_initial[] = {
  &_swigt__p_char,
  &_swigt__p_p_char,
};
 
static swig_cast_info _swigc__p_char[] = {  {&_swigt__p_char, 0, 0, 0},{0, 0, 0, 0}};
static swig_cast_info _swigc__p_p_char[] = {  {&_swigt__p_p_char, 0, 0, 0},{0, 0, 0, 0}};
 
static swig_cast_info *swig_cast_initial[] = {
  _swigc__p_char,
  _swigc__p_p_char,
};
 
 
/* -------- TYPE CONVERSION AND EQUIVALENCE RULES (END) -------- */
 
static swig_const_info swig_const_table[] = {
{0, 0, 0, 0.0, 0, 0}};
 
#ifdef __cplusplus
}

[varuns]

Hallo again verun
I hope the following code of interface_wrap.c is helpful.Thank you again.

extern "C" {
#endif
SWIGINTERN PyObject *_wrap_main(PyObject *SWIGUNUSEDPARM(self), PyObject *args) {
PyObject *resultobj = 0;
int arg1 ;
char **arg2 = (char **) 0 ;
int result;
int val1 ;
int ecode1 = 0 ;
void *argp2 = 0 ;
int res2 = 0 ;
PyObject * obj0 = 0 ;
PyObject * obj1 = 0 ;

if (!PyArg_ParseTuple(args,(char *)"OO:main",&obj0,&obj1)) SWIG_fail;
ecode1 = SWIG_AsVal_int(obj0, &val1);
if (!SWIG_IsOK(ecode1)) {
SWIG_exception_fail(SWIG_ArgError(ecode1), "in method '" "main" "', argument " "1"" of type '" "int""'");
}
arg1 = (int)(val1);
res2 = SWIG_ConvertPtr(obj1, &argp2,SWIGTYPE_p_p_char, 0 | 0 );
if (!SWIG_IsOK(res2)) {
SWIG_exception_fail(SWIG_ArgError(res2), "in method '" "main" "', argument " "2"" of type '" "char **""'");
}
arg2 = (char **)(argp2);
result = (int)main(arg1,arg2);
resultobj = SWIG_From_int((int)(result));
return resultobj;
fail:
return NULL;
}


static PyMethodDef SwigMethods[] = {
{ (char *)"main", _wrap_main, METH_VARARGS, NULL},
{ NULL, NULL, 0, NULL }
};


/* -------- TYPE CONVERSION AND EQUIVALENCE RULES (BEGIN) -------- */

static swig_type_info _swigt__p_char = {"_p_char", "char *", 0, 0, (void*)0, 0};
static swig_type_info _swigt__p_p_char = {"_p_p_char", "char **", 0, 0, (void*)0, 0};

static swig_type_info *swig_type_initial[] = {
&_swigt__p_char,
&_swigt__p_p_char,
};

static swig_cast_info _swigc__p_char[] = { {&_swigt__p_char, 0, 0, 0},{0, 0, 0, 0}};
static swig_cast_info _swigc__p_p_char[] = { {&_swigt__p_p_char, 0, 0, 0},{0, 0, 0, 0}};

static swig_cast_info *swig_cast_initial[] = {
_swigc__p_char,
_swigc__p_p_char,
};


/* -------- TYPE CONVERSION AND EQUIVALENCE RULES (END) -------- */

static swig_const_info swig_const_table[] = {
{0, 0, 0, 0.0, 0, 0}};

#ifdef __cplusplus
}

hi
sorry for the late responce
i think you need to manually write for (int argc,char *argv[])
try this code in your .i file

%typemap(in) (int argc, char *argv[]) {
  int i;
  if (!PyList_Check($input)) {
    PyErr_SetString(PyExc_ValueError, "Expecting a list");
    return NULL;
  }
  $1 = PyList_Size($input);
  $2 = (char **) malloc(($1+1)*sizeof(char *));
  for (i = 0; i < $1; i++) {
    PyObject *s = PyList_GetItem($input,i);
    if (!PyString_Check(s)) {
        free($2);
        PyErr_SetString(PyExc_ValueError, "List items must be strings");
        return NULL;
    }
    $2[i] = PyString_AsString(s);
  }
  $2[i] = 0;
}
 
%typemap(freearg) (int argc, char *argv[]) {
   if ($2) free($2);
}

[nimitsis]

I try to and it works. Thank you a lot varuns.

[Nicky Wang]

Hello, varuns.
I also meet a similar question, I don't know how to deal with the arguments of the main() function, should I replace the main() function in the c file? Thanks