Py_ParseTuple Problem

**Rick L. Ratzel** · Jul 18 '05, 10:23 AM

Re: Py_ParseTuple Problem

I'm assuming you mean PyArg_Parse and PyArg_ParseTupl e? I couldn't find
any docs on Py_Parse or Py_ParseTuple.. .

Anyway, maybe something like this might work for you (portions taken
from example in http://elmer.sourceforge.net/PyCon04...pycon04.html):

....
PyObject* evalModule;
PyObject* evalDict;
PyObject* evalVal;
PyObject* tupleItem;
unsigned char* my_c_array;
int i;
int tupleSize;

PyRun_SimpleStr ing( "result = pyFuncWhichRead sDevice()" )

evalModule = PyImport_AddMod ule( (char*)"__main_ _" );
evalDict = PyModule_GetDic t( evalModule );
evalVal = PyDict_GetItemS tring( evalDict, "result" );

if( evalVal == NULL ) {
PyErr_Print();
exit( 1 );

} else {
if( !PyTuple_Check( evalVal ) ) {
printf( "Error: pyFuncWhichRead sDevice() did not return a tuple" );
exit( 1 );
}

my_c_array = (unsigned char*) malloc( sizeof( unsigned char ) *
PyTuple_Size( evalVal ) );

tupleSize = PyTuple_Size( evalVal );

for( i=0; i < tupleSize; i++ ) {
tupleItem = PyTuple_GetItem ( evalVal, i );

if( !PyInt_Check( tupleItem ) ) {
printf( "Error: pyFuncWhichRead sDevice() returned tuple with
non-int value" );
exit( 1 );
}
my_c_array[i] = (unsigned char) PyInt_AsLong( tupleItem );
}
}
....

I have no idea if this will work for you since I haven't even tried
to compile it...consider it pseudo-code.

-Rick.

youngdubliner@h otmail.com wrote:[color=blue]
> Hi All ,
>
> Bit of a problem with Py_Parse or Py_ParseTuple ?
>
> I have a python script that reads a sector of flash in an embedded device.
> it returns the value of each byte within the sector as a tuple.
>
> i.e. [255,255,255,255 ,255,255,255, .......etc etc for the whole sector !
>
> We are using this script to read whats currently in any sector.
> No problems there.
>
> Now I need to call our script from C.
>
> I want to copy each of the bytes within the sector into an C unsigned char *array
>
> Is there any way to do this using Py_ParseTuple or Py_Parse ???
>
> something like this for instance ??? ......
>
> Py_ParseTuple[pres,"??",&my_c _array]
>
> so now my_c_array[0] = 255 ,my_c_array[1] = 255 ,my_c_array[2] = 255 , etc etc
>
>
> Thanks for the help ![/color]

**Terry Reedy** · Jul 18 '05, 10:24 AM

Re: Py_ParseTuple Problem

<youngdubliner@ hotmail.com> wrote in message
news:4039221c.0 404202256.3f21d 817@posting.goo gle.com...[color=blue]
> Hi All ,
>
> Bit of a problem with Py_Parse or Py_ParseTuple ?
>
> I have a python script that reads a sector of flash in an embedded[/color]
device.[color=blue]
> it returns the value of each byte within the sector as a tuple.
>
> i.e. [255,255,255,255 ,255,255,255, .......etc etc for the whole sector ![/color]

As written, above is a list instead of a tuple.
[color=blue]
> We are using this script to read whats currently in any sector.
> No problems there.
>
> Now I need to call our script from C.
>
> I want to copy each of the bytes within the sector into an C unsigned[/color]
char *array

Without knowing the C API, I would try to generate byte string from within
Python. Three possibilities:

1. turn list into string - secstring = ''.join(map(chr , seclist)). Then
use C API to get the cstring from string object.

2. turn list/tuple into array (of unsigned chars) or built that directly
instead of list or tuple. See array module. I presume you can get at the
buffer itself from C API.

3. look into ctypes module.
[color=blue]
> Is there any way to do this using Py_ParseTuple or Py_Parse ???[/color]

If you mean PyArg.... stuff, I believe these are meant for parsing
argu;ments passed as heterogeneous Python tuple, which is quite different
from what you want to do.

Terry J. Reedy

**youngdubliner@hotmail.com** · Jul 18 '05, 10:25 AM

Re: Py_ParseTuple Problem

Thanks Rick ,

Thats excellent I tried your code , changed it a little and it works
really well.

I didn't even know that PyTuple_Size() existed , handy little function that.

Thanks again !

Keith.

Py_ParseTuple Problem

Py_ParseTuple Problem

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